serratia infections from military experiments to current practice

• DOI: 10.1128/CMR.00017-11
• Corpus ID: 206737855

Serratia Infections: from Military Experiments to Current Practice

• Steven D. Mahlen
• Published in Clinical Microbiology Reviews 1 October 2011

477 Citations

Serratia marcescens infections in neonatal intensive care units (nicus), a rare presentation of infective endocarditis due to serratia marcescens, sepsis neonatal por serratia marcescens asociada con nutrición parenteral total, serratia fonticola, pathogen or bystander a case series and review of the literature, serratia myositis in an intravenous drug user.

• Highly Influenced

Global population structure of the Serratia marcescens complex and identification of hospital-adapted lineages in the complex

A sixty-nine-year-old female with serratia marcescens infection, cutaneous serratia marcescens infections in korea: a retrospective analysis of 13 patients, healthcare-associated infections caused by chlorhexidine-tolerant serratia marcescens carrying a promiscuous inchi2 multi-drug resistance plasmid in a veterinary hospital, molecular characterization of serratia marcescens strain isolated from yellow mealworms, tenebrio molitor, in the netherlands, 450 references, serratia marcescens isolated in 2005 from clinical specimens from patients with diminished immunity., overgrowth of serratia marcescens in respiratory tract, simulating hemoptysis; report of a case., extended epidemic of nosocomial urinary tract infections caused by serratia marcescens, role of serratia species in urinary tract infections., serratia marcescens bacteremia – an indicator for outbreak management and heightened surveillance.

• Highly Influential

Serratia ficaria: a Misidentified or Unidentified Rare Cause of Human Infections in Fig Tree Culture Zones

[serratia rubidaea bacteremia]., pseudomonas aeruginosa, an outbreak of nosocomial infection due to multiply resistant serratia marcescens: evidence of interhospital spread., serratia marcescens infections in neonatal departments: description of an outbreak and review of the literature., related papers.

Showing 1 through 3 of 0 Related Papers

Pascal and Francis Bibliographic Databases

Selection :

• Selected items ( 1 )

Serratia Infections: from Military Experiments to Current Practice

Clinical microbiology reviews (Print) . 2011, Vol 24, Num 4 ; III, 755-791 [38 p.] ; ref : 427 ref

Sauf mention contraire ci-dessus, le contenu de cette notice bibliographique peut être utilisé dans le cadre d’une licence CC BY 4.0 Inist-CNRS / Unless otherwise stated above, the content of this bibliographic record may be used under a CC BY 4.0 licence by Inist-CNRS / A menos que se haya señalado antes, el contenido de este registro bibliográfico puede ser utilizado al amparo de una licencia CC BY 4.0 Inist-CNRS

Access to the document

Searching the Web

GENERAL COMMENTARY article

Serratia marcescens : an outbreak experience.

• Institute of Hygiene and Environmental Health, Charité - University Medicine Berlin, Berlin, Germany

One year ago, I had one of the worst experiences a hospital epidemiologist can have: a Serratia marcescens outbreak in a neonatal department with a total of 21 colonized or infected newborns. This outbreak caused headlines in all national TV channels and newspapers for at least one week in Germany.

What happened? On October 8th, we identified two newborns with S. marcescens bloodstream infection on the same day. The local health authorities were informed, the infected infants were isolated and staff was educated about the special risks of Serratia infections. In addition, environmental samples were taken to search for an external source and a general screening of all newborns of this neonatal intensive care unit was performed to identify possible additional colonized cases. After detecting further colonized patients, we extended the screening to two other neonatal wards and found more neonates colonized with S. marcescens . Because the units were unable to isolate all colonized neonates with the available staff, the hospital director decided to close the department for new admissions on October 18th. This was the reason why the media became interested and asked for an explanation. One colonized infant born with a severe heart defect was transferred to another hospital for heart surgery and died some days after the operation. The supposition of the media was that the infection had caused the infant's death and it was not as a result of the severe heart defect. As a consequence, the State Attorney's Office opened an investigation into negligent manslaughter by persons unknown.

Our experience is in strong contrast with the knowledge about S. marcescens about 50 years ago. Until the 1950s, microbiologists considered this pathogen a harmless saprophyte. Because of its red pigment it served as a tracer organism to identify the spread of other microorganisms such as influenza viruses. It was used in World War I and until 1968 for military experiments to investigate transmission of pathogens ( Mahlen, 2011 ). The first description of lethal S. marcescens cases in newborns was published in 1961 ( Urmenyi and Franklin, 1961 ). A report from our own institution from 1989 described a prolonged outbreak with 222 cases of neonatal septicemia and/or meningitis in the period between 1983 and 1988. The incidence was 8.46 per 1000 liveborn infants. The case fatality rate amounted to 45.9%. ( Grauel et al., 1989 ).

Current data from the German national nosocomial surveillance system for very low birth weight (VLBW) infants with 234 neonatal units participating show that 1.2% of blood stream infections with an identified pathogen are due to S. marcescens . The incidence of nosocomial infections with S. marcescens was 1.1 per 1000 VLBW in the period from 2008 to 2012 ( Nationales Referenzzentrum für die Surveillance von nosokomialen Infektionen Available online at: http://www.nrz-hygiene.de ).

However, the proportion of S. marcescens infections is much higher when analyzing outbreak data. S. marcescens had the third highest number of published outbreaks following Klebsiella spp. and S. aureus ( Gastmeier et al., 2007 ). In most of the published neonatal S. marcescens outbreaks, it was impossible to identify the source of the outbreak. A recent query of the Worldwide Database with more than 3000 nosocomial outbreaks published in the literature ( www.outbreak-database.com ) identified 109 S. marcescens outbreaks. Forty-eight of these outbreaks (44%) were described in neonatal units. The average number of cases in the neonatal outbreaks was 33 with a range from 4 to 159. In about 60% of S. marcescens outbreaks in neonatal departments, it was impossible to identify the source (Table 1 ).

Table 1. Distribution of outbreak sources for neonatal S. marcescens outbreaks .

Of course, the published outbreaks are only the tip of the iceberg, and one can expect that at least 2–3 S. marcescens outbreaks occur annually in German neonatal intensive care units ( Schwab et al., 2014 ).

One year later, the State Attorney's Office closed its investigation in Berlin and concluded on the basis of an autopsy by two pathologists that the death was not due to negligence (but rather because of the birth defect) and that were no cases of physical injury due to negligence. The hospital's infection control measures, they concluded, were appropriate. Among more than 600 environmental samples, we did not find any evidence for an environmental source. Looking back, it became clear that a mother with an amnion infection syndrome and identification of S. marcescens three months earlier was perhaps the source of the outbreak. She infected her infant and a further infant was colonized, but we did not find any other infected of colonized patients in the surrounding of these newborns. This child was also transferred to the heart surgery center and came back some weeks later.

One year after the outbreak, we can say that after identifying all colonized neonates in the first week of the outbreak by the extensive screening, no further neonates became infected although the last infant of the outbreak group was discharged 7 months later. In addition, scientists have shown by whole genome sequencing that that our S. marcescens strain had special virulence factors which lead to a rapid spread of this microorganism (submitted).

A recently published article analyzing fecal microbiota during the first month of life concluded that the presence of Serratia was strongly associated with a higher degree of immaturity and other hospital-related parameters, including antibiotic therapy and mechanical ventilation ( Moles et al., 2013 ). This means that S. marcescens remains a dangerous pathogen in neonatal intensive care units. Our S. marcescens strain was a susceptible one, but the problem may even increase when resistant strains cause outbreaks. In 2013, the first outbreak with a Carbapenemase-producing S. marcescens was published in Argentina ( Nastro et al., 2013 ).

Gastmeier, P., Loui, A., Stamm-Balderjahn, S., Hansen, S., Zuschneid, I., Sohr, D., et al. (2007). Outbreaks in neonatal intensive care units- they are not like others. Am. J. Infect. Control . 35, 172–176. doi: 10.1016/j.ajic.2006.07.007

CrossRef Full Text

Grauel, E., Halle, E., Bollmann, R., Buchholz, P., and Buttenberg, S. (1989). Neonatal septicaemia—incidence, etiology and outcome. A 6-year analysis. Acta Paediatr. Scand. Suppl . 360, 113–139. doi: 10.1111/j.1651-2227.1989.tb11291.x

Pubmed Abstract | Pubmed Full Text | CrossRef Full Text

Mahlen, S. (2011). Serratia infections: from military experiments to current practice. Clin. Microbiol. Rev . 24, 755–791. doi: 10.1128/CMR.00017-11

Moles, L., Gómez, M., Heilig, H., Bustos, G., Fuentes, S., de Vos, W., et al. (2013). Bacterial diversity in meconium of preterm neonates and evolution of their fecal microbiota during the first month of life. PLoS ONE . 8:e66986. doi: 10.1371/journal.pone.0066986

Nastro, M., Monge, R., Zintgraff, J., Vaulet, L., Boutureira, M., Famiglietti, A., et al. (2013). First nosocomial outbreak of VIM-16-producing Serratia marcescens in Argentina. Clin. Microbiol. Infect . 19, 617–619. doi: 10.1111/j.1469-0691.2012.03978.x

Nationales Referenzzentrum für die Surveillance von nosokomialen Infektionen. Available online at: http://www.nrz-hygiene.de

Schwab, F., Geffers, C., Piening, B., Haller, S., Eckmanns, T., and Gastmeier, P. (2014). How many outbreaks of nosocomial infections occur in German neonatal intensive care units annually? Infection 42, 73–78. doi: 10.1007/s15010-013-0516-x

Urmenyi, A., and Franklin, A. (1961). Neonatal death from pigmented coliform infection. Lancet 1, 313–315. doi: 10.1016/S0140-6736(61)91481-7

Keywords: Serratia marcescens , outbreak, neonates, infection control, multiresistance

Citation: Gastmeier P (2014) Serratia marcescens : an outbreak experience. Front. Microbiol . 5 :81. doi: 10.3389/fmicb.2014.00081

Received: 07 January 2014; Accepted: 14 February 2014; Published online: 06 March 2014.

Copyright © 2014 Gastmeier. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: [email protected]

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

Volume 30, Supplement - Infectious Diseases and Carceral Health SUPPLEMENT ISSUE

Outbreaks and investigations, outbreak of invasive serratia marcescens among persons incarcerated in a state prison, california, usa, march 2020–december 2022.

Cite This Article

Serratia marcescens is an environmental gram-negative bacterium that causes invasive disease in rare cases. During 2020–2022, an outbreak of 21 invasive Serratia infections occurred in a prison in California, USA. Most (95%) patients had a history of recent injection drug use (IDU). We performed whole-genome sequencing and found isolates from 8 patients and 2 pieces of IDU equipment were closely related. We also identified social interactions among patients. We recovered S. marcescens from multiple environmental samples throughout the prison, including personal containers storing Cell Block 64 (CB64), a quaternary ammonium disinfectant solution. CB64 preparation and storage conditions were suboptimal for S. marcescens disinfection. The outbreak was likely caused by contaminated CB64 and propagated by shared IDU equipment and social connections. Ensuring appropriate preparation, storage, and availability of disinfectants and enacting interventions to counteract disease spread through IDU can reduce risks for invasive Serratia infections in California prisons.

Serratia marcescens , a gram-negative environmental bacterium ( 1 , 2 ), is an opportunistic pathogen that in rare cases causes invasive diseases, including bacteremia and endocarditis ( 1 , 3 – 7 ). Reported outbreaks have been linked to contaminated environmental sources, such as water, soap, intravenous fluids, and compounded drugs ( 8 – 16 ) in nosocomial settings ( 17 – 19 ). Invasive S. marcescens infections have occurred among persons who inject drugs ( 5 , 6 , 20 – 22 ). Given the high prevalence of injection drug use (IDU) in prisons and lack of access to sterile needles ( 23 – 25 ), risks for transmission of bloodborne pathogens are higher than among the general population ( 25 ). Cell Block 64 (CB64) solution, produced by California Prison Industry (CALPIA, https://www.calpia.ca.gov ), is a quaternary ammonium concentrate ( https://catalog.calpia.ca.gov/custom/assets/Files/view-current-sds-information-16.pdf ) used as the primary disinfectant in prisons in California, USA. However, S. marcescens can survive in improperly prepared disinfection solutions, including quaternary ammonium disinfectants ( 18 , 19 , 26 ).

We describe a multiyear outbreak of invasive S. marcescens infections driven by widespread environmental contamination, improperly prepared and maintained disinfection solution, IDU, and social connections at a California state prison. Prison A is a maximum-security state prison housing ≈3,000 male incarcerated persons. In October 2020, the primary hospital affiliated with prison A notified the California Correctional Health Care System (CCHCS) that multiple incarcerated persons had been admitted with invasive S. marcescens infections. CCHCS, Monterey County Public Health Laboratory (MCPHL), and California Department of Public Health (CDPH) began a multidisciplinary investigation to identify additional cases, determine risk factors for infection, and provide recommendations for mitigation and prevention. This project was determined to be nonresearch by the Centers for Disease Control and Prevention because it involved public health surveillance.

Materials and Methods

Epidemiologic investigation.

We defined a case-patient as a person diagnosed with an invasive S. marcescens infection who resided at prison A for ≥1 month before symptom onset during January 1, 2020–December 31, 2022. We defined infections as invasive if occurring at normally sterile body sites or in a case-patient manifesting critical illness with severe soft tissue infection. We reviewed patient hospitalization and prison medical records, including social histories, for IDU and other risk-elevating behaviors. We interviewed patients using a standardized questionnaire that included questions about cell cleaning practices, IDU, and other risk factors.

Environmental Investigation

Prison A public health and infection control, CCHCS public health, CDPH, and MCPHL staff evaluated the water system and cleaning practices and procedures at prison A. In 2020 and 2021, MCPHL tested water from different sources at prison A, including holding tanks and wells. MCPHL also tested sinks and communal showers, faucets in patients’ cells, personal items, hand-rinsate from a cellmate, 2 syringes used for injecting drugs, objects used for mixing, storing, or applying disinfectant, dilution machines, reused containers, and commercial bottles.

Laboratory Investigation

MCPHL streaked swabs onto Serratia CHROMagar ( https://www.chromagar.com ) MacConkey and blood agar plates and incubated them in brain heart infusion broth for up to 5 days. Needles and syringes were placed directly into brain heart infusion broth. Cultures with growth were subcultured on CHROMagar plates. Liquids, including water, disinfectant cleaning solutions, and rinsates, were filtered onto 47 mm 0.45 μm–pore sized mixed cellulose ester membranes and placed onto CHROMagar plates. MCPHL forwarded S. marcescens isolates to CDPH Center for Laboratory Science Microbial Diseases Laboratory for whole genome sequencing (WGS) using the validated in-house protocol with Illumina MiSeq ( https://www.illumina.com ) ( Appendix ) ( 27 ).

• Figure 1 . Epidemiologic curve of patients hospitalized with invasive Serratia marcescens infections at prison A, by sampling month of positive isolate, California, USA, January 2020–March 2023.

As of December 2022, we had identified 21 cases: 17 identified during March 2020–August 2021 and 4 during April–October 2022 ( Figure 1 ). All 21 case-patients were hospitalized and recovered; however, 1 patient later died of a cause unrelated to S. marcescens . Median patient age was 44 years (range 22–66 years). We grouped patients by race/ethnicity as non-Hispanic White (9 [43%]), non-Hispanic Black (2 [10%]), Hispanic (8 [38%]), or other (2 [10%]). Diagnoses were not mutually exclusive and included bacteremia in 11 (52%) patients; endocarditis in 2 (10%); epidural abscess in 9 (43%); osteomyelitis in 6 (29%); pseudoaneurysm in 1 (5%); and soft tissue infections in 4 (19%), including 2 (10%) with muscle abscess ( Table 1 ). Of the nonbacteremic patients, 2 had polymicrobial cultures, including viridans streptococci ( 1 ), Staphylococcus aureus ( 2 ), and Raoutella panticola ( 1 ).

Twenty (95%) patients had a history of IDU <6 months before infection and one >6 months before infection. Of patients with recent IDU, 18/20 (86%) had injected heroin, 12 (57%) suboxone, and 8 (38%) methamphetamines. Among patients who had urine toxicology performed at admission, 4/9 were positive for opiates. Nine patients reported consuming >1 drug; 5 patients used 2 and 4 patients used 3 drugs. Of patients interviewed, 5/16 (31%) used CB64 to clean IDU equipment. Of PWID patients, 9/21 (43%) were enrolled in the prison A substance use disorder treatment (SUDT) program before S. marcescens infection occurred.

• Figure 2 . Social network analysis of patients and whole genome sequencing results for patients hospitalized with invasive Serratia marcescens infections at prison A, California, USA, January 2020–March 2023. All patients were...

Figure 3 . Phylogenetic tree representing patients hospitalized with invasive Serratia marcescens infections and whole-genome sequencing for environmental and clinical isolates at prison A, California, USA, January 2020–March 2023. The predominant outbreak...

Although some patients resided throughout the 4 physically separated yards at the facility, 11 (52%) were housed in yard 1; 2 patients in other yards at time of illness onset had previously been housed in yard 1. Interviews identified social connections among >9 patients. We used WGS to identify the predominant S. marcescens outbreak strain as the cause of infection in 6 (66%) patients and a different strain in 1 patient; we had no isolates available for 4 patients ( Figures 2 , 3 ). Among patients who revealed social connections, 6 shared needles, 4 shared cells, 3 had attended the urgent care clinic at the same time, and 2 might have shared tattoo needles ( Figure 2 ). Patient AC, diagnosed with an invasive S. marcescens infection at a different prison in 2019 and later transferred to prison A, was found to have multiple social connections with patients identified in 2020 and beyond but we did not include him in the outbreak cohort ( Figure 2 ).

Figure 4 . Device calibrated to dilute Cell Block 64 solution and other cleaners to correct concentrations. Device pictured shows dangling tubing touching the machine surface, a possible route of contamination in outbreak...

Inspection of the potable water system at prison A did not identify any deficiencies or areas of concern, and we found large-volume water samples negative for Serratia. Each housing unit has a machine for diluting the CB64 solution ( Figure 4 ). Machines in multiple units had exposed tubing touching the machine surface, maintenance schedules were not documented, and dilution of CB64 occurred in large containers outside the dilution machines. Prison A allowed incarcerated persons to keep CB64 in their cells after the COVID-19 pandemic started. Some incarcerated persons described using their own repurposed containers (e.g., shampoo bottles) to scoop diluted CB64 from the large containers.

Eleven patients had isolates available for WGS; 8 (73%) patients, including 3 identified in 2022, had isolates that differed from one another by 0–19 single-nucleotide polymorphisms (SNPs) on WGS. Those isolates clustered within the predominant strain group ( Figure 3 ). Of 152 environmental samples collected and analyzed, 27 (18%) were positive for S. marcescens , including a needle and syringe combination (sample I) and a reused nasal spray bottle (sample C) storing methamphetamines from patient D ( Table 2 ). Both specimens matched the predominant outbreak strain ( Figure 3 ). The S. marcescens isolate from patient F grouped within 11–17 SNPs with isolates from a coffee cup (sample B) found in patient D’s cell, hand-rinsate (sample H) from patient D’s cellmate, and a doorway swab (sample Y) from a cell occupied at different times by patients AA and AC ( Table 2 ; Figure 3 ). All other isolates differed from the predominant strain by thousands of SNPs ( Figure 3 ). We sequenced multiple isolates from some samples. Samples from all unopened bottles of CB64 tested negative for S. marcescens .

During March 2020–December 2022, a total of 21 persons incarcerated at prison A required hospitalization for invasive Serratia infections. Factors contributing to this outbreak included widespread environmental contamination with Serratia, including in CB64, the sole disinfectant used within the prison, and complex social networks that involved IDU.

Of note, 5 environmental samples that tested positive for Serratia were associated with diluted CB64. CB64 is used throughout California state prisons as a disinfectant because it is less caustic than other disinfectants (e.g., bleach). Quaternary ammonium compounds like CB64 have previously been linked to outbreaks ( 18 , 19 , 26 ). Prison A had documented nonadherence to CB64 manufacturer dilution and storage protocols. In addition, incarcerated persons stored diluted CB64 in cells after the COVID-19 pandemic began, a change in procedure occurring at approximately the same time as initial cases. Repeatedly finding Serratia in CB64 indicates that improper use and storage of the disinfectant likely contributed to the spread.

The invasive nature of the Serratia infections, including manifestations such as bacteremia and severe soft-tissue infection, suggests introduction of the bacteria directly into the bloodstream or soft tissues, highlighting the role of IDU in the prison outbreak. The predominant outbreak strain of Serratia was recovered from a needle obtained from 1 patient. In prisons, there is no access to new needles; some patients reported sharing needles, and most reported reusing needles multiple times themselves. Some patients reported using CB64 to clean their needles.

In August 2021, prison A implemented mitigation measures, including extensive staff training, instituting maintenance logs, recalibrating dilution machines, ensuring regular changing of tubing in dilution devices, and providing dedicated bottles of CB64 for incarcerated persons to check out and return within 24 hours for in-cell cleaning. Additional education on IDU risks and SUDT (begun in 2020) were also provided to incarcerated persons. No new cases were identified until spring 2022, at which time lapses in staff and resident education on use, maintenance, and storage of CB64 solution and dilution devices were recognized.

WGS results for 3 patient isolates identified at the prison in 2022 were closely related to 2021 patient isolates, indicating that the predominant outbreak strain of S. marcescens persisted >1 year . Given the diversity of S. marcescens strains in the environment, the predominance of a single strain suggests the likely existence of a persistent, but unknown, nidus of the outbreak strain. A single contaminated drug or CB64 source is unlikely to account for the persistence. An incarcerated person colonized with this strain or an unrecognized fomite in the environment are possible sources. Although S. marcescens is not a normal part of human flora, colonization of skin and gut has been documented ( 10 , 27 ). In addition, the hand-rinsate from a patient’s cellmate yielded S. marcescens , indicating the potential for persistence on skin. After identification of additional cases in 2022, intervention included reeducating staff and incarcerated persons on proper use of CB64, including performing dilution within dilution devices only, and education on risks for S. marcescens infection through IDU equipment. No further cases had been documented as of July 2023, 8 months after the last identified case. Additional education has been provided to institutions throughout the state ( Appendix ).

One limitation of this study is that, given drug use is prohibited in prison, patients might have provided incomplete information regarding drug preparation and sharing, and therefore some common sources of drugs or drug equipment may not have been identified. In addition, only 2 needles or syringes were available for testing. A comprehensive environmental sampling survey of the entire prison population and structure was unfeasible, so we focused testing on areas where cases were identified. Additional sources of environmental contamination, including water sources such as cell toilet water and shower and sink drains and traps, where biofilm may have formed, were unable to be tested. A limited number of patient isolates from 2021 and 2022 were available for WGS; testing of all isolates might have further clarified patient connections. Patients might have been infected with >1 S. marcescens strain. Most environmental isolates positive for S. marcescens did not match patient strains, and so direct correlation between environmental contamination and patient illness was not possible. Finally, our investigation focused on invasive infections and excluded milder illness.

Beginning in January 2020, screening and referral for SUDT became available in California prisons to all newly incarcerated persons, those transitioning into the community, and patients with IDU-related complications ( 28 ). As of January 2022, >64,600 incarcerated persons had been screened for SUD and medication-assisted treatment provided to >22,500 patients, leading to a significantly decline in overdoses and infectious disease complications since the program started ( 29 ).

After this outbreak, queries have identified additional cases of invasive S. marcescens infections in other California prisons. Similar concerns related to disinfection, including improper storage, device calibration, and usage, and IDU practices have been reported. Environmental mitigation through extensive cleaning and strict adherence to disinfectant guidelines might not eliminate all environmental sources of Serratia but might decrease the environmental microbial burden, thereby decreasing potential exposures to S. marcescens and other pathogens. IDU among incarcerated persons should be addressed through promotion of harm reduction practices and education, including access to appropriate disinfection supplies and sterile needles, and referral to SUDT programs.

Dr. Kamali is a medical epidemiologist and infectious disease physician with California Correctional Health Care Services and California Department of Public Health whose interests include outbreak investigation.

Acknowledgments

We thank Allen Radner, Andrew Massengill, Darlene Brieno, Lucy Tompkins, Stanley Deresinski, Jonathon Yoder, Matthew Arduino, Mia Mattioli, and Jon Rosenberg. We also thank the incarcerated persons, patients, and staff of the California Department of Corrections and Rehabilitation (prison A).

Laboratory investigation was supported the Centers for Disease Control and Prevention through a grant on the epidemiology and laboratory capacity for infectious diseases from (grant no. 5NU50CK000539) and by the California General Fund.

Author contributions: concept/design: A.Ka., N.O., H.B., A.Y., and A.Ki.; data acquisition: A.Ka., D.F., H.D., N.O., R.M., R.L., J.C., A.Y., and A.Ki.; data analysis: A.Ka., D.F., C.S., R.L., J.H., J.C., A.Y., and A.Ki.; draft: A.Ka., C.S., A.Y., and A.Ki.; revision: A.Ka., D.F., H.D., N.O., R.M., C.S., R.L., J.H., M.S., H.B., A.Y., and A.Ki.

• Fisher  RG . Serratia. In: Feigin RD, Cherry JD, Demmler-Harrison GJ, Kaplan SL, eds. Feigin and Cherry’s textbook of pediatric infectious diseases (6th edition). Philadelphia: W.B. Saunders, 2009 . pp. 1563–7.
• Donnenberg  MS . Enterobacteriaceae. Bennett JE, Dolin R, and Blaser MJ, eds. Mandell, Douglas, and Bennett’s principles and practice of infectious diseases, 8th edition. Philadelphia: W.B. Saunders, 2015 . p. 2503–17.e5.
• Mahlen  SD . Serratia infections: from military experiments to current practice. Clin Microbiol Rev . 2011 ; 24 : 755 – 91 . DOI PubMed Google Scholar
• Rana  A , Rabbani  NUA , Wood  S , McCorkle  C , Gilkerson  C . A complicated case of vertebral osteomyelitis by Serratia marcescens. Cureus . 2020 ; 12 : e9002 . DOI PubMed Google Scholar
• Sanchez  KT , Johnson  LB , Szpunar  S , Saravolatz  LD . A case of mixed Serratia marcescens and Streptococcus mitis endocarditis and review of the literature. Infect Dis Clin Pract . 2012 ; 20 : 245 – 7 . DOI Google Scholar
• Schecter  MC , Spicer  JO , Aldrete  SDM , Kraft  CS . Serratia marcescens infectious endocarditis injection drug use, left-sided heart disease, and poor outcomes. Infect Dis Clin Pract . 2018 ; 26 : 216 – 9 . DOI Google Scholar
• Hadid  H , Usman  M , Thapa  S . Severe osteomyelitis and septic arthritis due to Serratia marcescens in an immunocompetent patient. Case Rep Infect Dis . 2015 ; 2015 : 347652 . DOI PubMed Google Scholar
• Horcajada  JP , Martínez  JA , Alcón  A , Marco  F , De Lazzari  E , de Matos  A , et al. Acquisition of multidrug-resistant Serratia marcescens by critically ill patients who consumed tap water during receipt of oral medication. Infect Control Hosp Epidemiol . 2006 ; 27 : 774 – 7 . DOI PubMed Google Scholar
• Civen  R , Vugia  DJ , Alexander  R , Brunner  W , Taylor  S , Parris  N , et al. Outbreak of Serratia marcescens infections following injection of betamethasone compounded at a community pharmacy. Clin Infect Dis . 2006 ; 43 : 831 – 7 . DOI PubMed Google Scholar
• Cristina  ML , Sartini  M , Spagnolo  AM . Serratia marcescens  infections in neonatal intensive care units (NICUs). Int J Environ Res Public Health . 2019 ; 16 : 610 . DOI PubMed Google Scholar
• Caggiano  G , Triggiano  F , Diella  G , Apollonio  F , Lopuzzo  M , Mosca  A , et al. A possible outbreak by  Serratia marcescens : genetic relatedness between clinical and environmental strains. Int J Environ Res Public Health . 2021 ; 18 : 9814 . DOI PubMed Google Scholar
• Archibald  LK , Corl  A , Shah  B , Schulte  M , Arduino  MJ , Aguero  S , et al. Serratia marcescens outbreak associated with extrinsic contamination of 1% chlorxylenol soap. Infect Control Hosp Epidemiol . 1997 ; 18 : 704 – 9 . DOI PubMed Google Scholar
• Henry  B , Plante-Jenkins  C , Ostrowska  K . An outbreak of Serratia marcescens associated with the anesthetic agent propofol. Am J Infect Control . 2001 ; 29 : 312 – 5 . DOI PubMed Google Scholar
• Ostrowsky  BE , Whitener  C , Bredenberg  HK , Carson  LA , Holt  S , Hutwagner  L , et al. Serratia marcescens bacteremia traced to an infused narcotic. N Engl J Med . 2002 ; 346 : 1529 – 37 . DOI PubMed Google Scholar
• Boyce  JM , Havill  NL . In-use contamination of a hospital-grade disinfectant. Am J Infect Control . 2022 ; 50 : 1296 – 301 . DOI PubMed Google Scholar
• Weber  DJ , Rutala  WA , Sickbert-Bennett  EE . Outbreaks associated with contaminated antiseptics and disinfectants. Antimicrob Agents Chemother . 2007 ; 51 : 4217 – 24 . DOI PubMed Google Scholar
• de Boer  MG , Brunsveld-Reinders  AH , Salomons  EM , Dijkshoorn  L , Bernards  AT , van den Berg  PCM , et al. Multifactorial origin of high incidence of Serratia marcescens in a cardio-thoracic ICU: analysis of risk factors and epidemiological characteristics. J Infect . 2008 ; 56 : 446 – 53 . DOI PubMed Google Scholar
• Rohit  A , Suresh Kumar  D , Dhinakaran  I , Joy  J , Vijay Kumar  D , Kumar Ballamoole  K , et al. Whole-genome-based analysis reveals multiclone Serratia marcescens outbreaks in a non-Neonatal Intensive Care Unit setting in a tertiary care hospital in India. J Med Microbiol . 2019 ; 68 : 616 – 21 . DOI PubMed Google Scholar
• de Vries  JJ , Baas  WH , van der Ploeg  K , Heesink  A , Degener  JE , Arends  JP . Outbreak of Serratia marcescens colonization and infection traced to a healthcare worker with long-term carriage on the hands. Infect Control Hosp Epidemiol . 2006 ; 27 : 1153 – 8 . DOI PubMed Google Scholar
• Peterson  TC , Pearson  C , Zekaj  M , Hudson  I , Fakhouri  G , Vaidya  R . Septic arthritis in intravenous drug abusers: a historical comparison of habits and pathogens. J Emerg Med . 2014 ; 47 : 723 – 8 . DOI PubMed Google Scholar
• Phadke  VK , Jacob  JT . Marvelous but Morbid: Infective endocarditis due to Serratia marcescens. [Baltim Md] . Infect Dis Clin Pract (Baltim Md) . 2016 ; 24 : 143 – 50 . DOI PubMed Google Scholar
• Cooper  R , Mills  J . Serratia endocarditis. A follow-up report. Arch Intern Med . 1980 ; 140 : 199 – 202 . DOI PubMed Google Scholar
• Bick  JA . Infection control in jails and prisons. Clin Infect Dis . 2007 ; 45 : 1047 – 55 . DOI PubMed Google Scholar
• Davis  DM , Bello  JK , Rottnek  F . Care of incarcerated patients. Am Fam Physician . 2018 ; 98 : 577 – 83 . PubMed Google Scholar
• Hammett  TM . HIV/AIDS and other infectious diseases among correctional inmates: transmission, burden, and an appropriate response. Am J Public Health . 2006 ; 96 : 974 – 8 . DOI PubMed Google Scholar
• Nakashima  AK , Highsmith  AK , Martone  WJ . Survival of Serratia marcescens in benzalkonium chloride and in multiple-dose medication vials: relationship to epidemic septic arthritis. J Clin Microbiol . 1987 ; 25 : 1019 – 21 . DOI PubMed Google Scholar
• Kozyreva  VK , Truong  CL , Greninger  AL , Crandall  J , Mukhopadhyay  R , Chaturvedi  V . Validation and implementation of Clinical Laboratory Improvements Act—compliant whole-genome sequencing in the public health microbiology laboratory. J Clin Microbiol . 2017 ; 55 : 2502 – 20 . DOI PubMed Google Scholar
• Jones  SR , Amon  M , Falvey  C , Patrick  K . Serratia marcescens colonising the gut. Lancet . 1978 ; 1 : 1105 . DOI PubMed Google Scholar
• California Department of Corrections and Rehabilitation, California Correctional Health Care Services . Transforming substance use disorder treatment in California’s prison system. Impacts of the Integrated Substance Use Disorder Treatment Program 2019–2021, April 2022 [ cited 2023 May 1 ]. https://cchcs.ca.gov/wp-content/uploads/sites/60/ISUDT/Impacts-ISUDT-Program2019-22.pdf
• Figure 3 . Phylogenetic tree representing patients hospitalized with invasive Serratia marcescens infections and whole-genome sequencing for environmental and clinical isolates at prison A, California, USA, January 2020–March 2023. The predominant...
• Figure 4 . Device calibrated to dilute Cell Block 64 solution and other cleaners to correct concentrations. Device pictured shows dangling tubing touching the machine surface, a possible route of contamination in...
• Table 1 . Demographic data and other characteristics of 21 patients infected with invasive Serratia marcescens at prison A, California, USA, 2020–2022
• Table 2 . Environmental specimens positive for Serratia marcescens associated with patients hospitalized with invasive Serratia marcescens infections at prison A, California, USA, January 2020–March 2023

DOI: 10.3201/eid3013.230801

Table of Contents – Volume 30, Supplement—March 2024

Please use the form below to submit correspondence to the authors or contact them at the following address:

Amanda Kamali, California Correctional Health Care Services, 8260 Longleaf Dr, Elk Grove, CA 95758, USA

Comment submitted successfully, thank you for your feedback.

There was an unexpected error. Message not sent.

Article Citations

Highlight and copy the desired format.

Metric Details

Volume 30, Supplement—March 2024

Article Views: 1168

Data is collected weekly and does not include downloads and attachments. View data is from .

What is the Altmetric Attention Score?

The Altmetric Attention Score for a research output provides an indicator of the amount of attention that it has received. The score is derived from an automated algorithm, and represents a weighted count of the amount of attention Altmetric picked up for a research output.

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings
• My Bibliography
• Collections
• Citation manager

Save citation to file

Email citation, add to collections.

• Create a new collection
• Add to an existing collection

Add to My Bibliography

Your saved search, create a file for external citation management software, your rss feed.

• Search in PubMed
• Search in NLM Catalog
• Add to Search

Serratia infections: from military experiments to current practice

Affiliation.

• 1 Department of Pathology and Area Laboratory Services, Madigan Healthcare System, Tacoma, WA 98143, USA. [email protected]
• PMID: 21976608
• PMCID: PMC3194826
• DOI: 10.1128/CMR.00017-11

Serratia species, in particular Serratia marcescens, are significant human pathogens. S. marcescens has a long and interesting taxonomic, medical experimentation, military experimentation, and human clinical infection history. The organisms in this genus, particularly S. marcescens, were long thought to be nonpathogenic. Because S. marcescens was thought to be a nonpathogen and is usually red pigmented, the U.S. military conducted experiments that attempted to ascertain the spread of this organism released over large areas. In the process, members of both the public and the military were exposed to S. marcescens, and this was uncovered by the press in the 1970s, leading to U.S. congressional hearings. S. marcescens was found to be a certain human pathogen by the mid-1960s. S. marcescens and S. liquefaciens have been isolated as causative agents of numerous outbreaks and opportunistic infections, and the association of these organisms with point sources such as medical devices and various solutions given to hospitalized patients is striking. Serratia species appear to be common environmental organisms, and this helps to explain the large number of nosocomial infections due to these bacteria. Since many nosocomial infections are caused by multiply antibiotic-resistant strains of S. marcescens, this increases the danger to hospitalized patients, and hospital personnel should be vigilant in preventing nosocomial outbreaks due to this organism. S. marcescens, and probably other species in the genus, carries several antibiotic resistance determinants and is also capable of acquiring resistance genes. S. marcescens and S. liquefaciens are usually identified well in the clinical laboratory, but the other species are rare enough that laboratory technologists may not recognize them. 16S rRNA gene sequencing may enable better identification of some of the less common Serratia species.

PubMed Disclaimer

Red-pigmented colonies of S. marcescens…

Red-pigmented colonies of S. marcescens on MacConkey agar (A), tryptic soy agar (B),…

Dendrogram of the genus Serratia,…

Dendrogram of the genus Serratia, constructed using the neighbor-joining method in MicroSeq software.…

Similar articles

• The ICU environment contributes to the endemicity of the " Serratia marcescens complex" in the hospital setting. Aracil-Gisbert S, Fernández-De-Bobadilla MD, Guerra-Pinto N, Serrano-Calleja S, Pérez-Cobas AE, Soriano C, de Pablo R, Lanza VF, Pérez-Viso B, Reuters S, Hasman H, Cantón R, Baquero F, Coque TM. Aracil-Gisbert S, et al. mBio. 2024 May 8;15(5):e0305423. doi: 10.1128/mbio.03054-23. Epub 2024 Apr 2. mBio. 2024. PMID: 38564701 Free PMC article.
• Natural antibiotic susceptibility of strains of Serratia marcescens and the S. liquefaciens complex: S. liquefaciens sensu stricto, S. proteamaculans and S. grimesii. Stock I, Grueger T, Wiedemann B. Stock I, et al. Int J Antimicrob Agents. 2003 Jul;22(1):35-47. doi: 10.1016/s0924-8579(02)00163-2. Int J Antimicrob Agents. 2003. PMID: 12842326
• Antibiotic susceptibility of Serratia marcescens and Serratia liquefaciens. Traub WH. Traub WH. Chemotherapy. 2000 Sep-Oct;46(5):315-21. doi: 10.1159/000007304. Chemotherapy. 2000. PMID: 10965096
• Serratia marcescens. Hejazi A, Falkiner FR. Hejazi A, et al. J Med Microbiol. 1997 Nov;46(11):903-12. doi: 10.1099/00222615-46-11-903. J Med Microbiol. 1997. PMID: 9368530 Review.
• [Serratia]. Hirakata Y. Hirakata Y. Nihon Rinsho. 2002 Nov;60(11):2156-60. Nihon Rinsho. 2002. PMID: 12440122 Review. Japanese.
• Targeted therapies in HER2-positive breast cancer with receptor-redirected Arazyme-linker-Herceptin as a novel fusion protein. Rahmani F, Ajoudanifar H, Arbab Soleimani N, Imani Fooladi AA. Rahmani F, et al. Breast Cancer. 2024 Aug 9. doi: 10.1007/s12282-024-01625-y. Online ahead of print. Breast Cancer. 2024. PMID: 39122876
• A Rare Infection Post Hyaluronic Acid Injection in the Trochanter: Case Report and Literature Review. Ahmed MB, Al-Mohannadi FS, Bensaoua A, Binfayed M, Alsherawi A. Ahmed MB, et al. Aesthet Surg J Open Forum. 2024 Jun 28;6:ojae052. doi: 10.1093/asjof/ojae052. eCollection 2024. Aesthet Surg J Open Forum. 2024. PMID: 39105124 Free PMC article.
• High Prevalence of Antibiotic Resistance in Traditionally Fermented Foods as a Critical Risk Factor for Host Gut Antibiotic Resistome. Li Y, Fu S, Klein MS, Wang H. Li Y, et al. Microorganisms. 2024 Jul 15;12(7):1433. doi: 10.3390/microorganisms12071433. Microorganisms. 2024. PMID: 39065201 Free PMC article.
• Microbial agents for the control of ticks Rhipicephalus microplus. Castro-Saines E, Lagunes-Quintanilla R, Hernández-Ortiz R. Castro-Saines E, et al. Parasitol Res. 2024 Jul 17;123(7):275. doi: 10.1007/s00436-024-08291-1. Parasitol Res. 2024. PMID: 39017922 Review.
• Opportunistic Pathogens in Drinking Water Distribution Systems-A Review. LeChevallier MW, Prosser T, Stevens M. LeChevallier MW, et al. Microorganisms. 2024 Apr 30;12(5):916. doi: 10.3390/microorganisms12050916. Microorganisms. 2024. PMID: 38792751 Free PMC article. Review.
• Aïtoff M., Dion M., Dobkevitch H. 1936. Bacillus prodigiosus pathogène pour les animoux: endotoxine et reaction de Shwartzman. C. R. Soc. Biol. 123:375–376(In French.)
• Ajithkumar B., Ajithkumar V. P., Iriye R., Doi Y., Sakai T. 2003. Spore-forming Serratia marcescens subsp. sakuensis subsp. nov., isolated from a domestic wastewater treatment tank. Int. J. Syst. Evol. Microbiol. 53:253–258 - PubMed
• Alexandrakis G., Alfonso E. C., Miller D. 2000. Shifting trends in bacterial keratitis in south Florida and emerging resistance to fluoroquinolones. Ophthalmology 107:1497–1502 - PubMed
• Al Jarousha A. M., El Qouqa I. A., El Jadba A. H. N., Al Afifi A. S. 2008. An outbreak of Serratia marcescens septicaemia in neonatal intensive care unit in Gaza City, Palestine. J. Hosp. Infect. 70:119–126 - PubMed
• Allison C., Coleman N., Jones P. L., Hughes C. 1992. Ability of Proteus mirabilis to invade human urothelial cells is coupled to motility and swarming differentiation. Infect. Immun. 60:4740–4746 - PMC - PubMed

Publication types

• Search in MeSH

Related information

Linkout - more resources, full text sources.

• Europe PubMed Central
• PubMed Central

Other Literature Sources

• The Lens - Patent Citations

• Citation Manager

NCBI Literature Resources

MeSH PMC Bookshelf Disclaimer

The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Unauthorized use of these marks is strictly prohibited.

Serratia Treatment & Management

• Author: Payal K Patel, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
• Sections Serratia
• Pathophysiology
• Epidemiology
• Laboratory Studies
• Imaging Studies
• Medical Care
• Surgical Care
• Consultations
• Medication Summary
• Antibiotics
• Further Inpatient Care
• Deterrence/Prevention
• Questions & Answers

​Serratia species can have multidrug resistance, particularly given the ability to induce AmpC β-lactamases. Infectious diseases consultation may be warranted. Antibiotic therapy is the primary treatment in most patients with serious  Serratia infection. Home therapy is an option in patients who are clinically stable.

Purulent collections (abscesses) may require drainage plus adjunctive antibiotic therapy.

Consult a cardiac surgeon if considering valve replacement in patients with infective endocarditis.

In a possible nosocomial outbreak of Serratia infection, strain typing may assist the epidemiologic investigation.

Infectious Diseases consultation may be warranted in formulating the optimal regimen for treatment. 

Donnenberg MS. Enterobacteriaceae. Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases . 7th. Philadelphia, Pa: Churchill Livingstone - Elsevier; 2010. Vol 2: 2815-2833.

Mahlen SD. Serratia infections: from military experiments to current practice. Clin Microbiol Rev . 2011 Oct. 24(4):755-91. [QxMD MEDLINE Link] . [Full Text] .

Carrero P, Garrote JA, Pacheco S, et al. Report of six cases of human infection by Serratia plymuthica. J Clin Microbiol . 1995 Feb. 33(2):275-6. [QxMD MEDLINE Link] .

Grohskopf LA, Roth VR, Feikin DR, et al. Serratia liquefaciens bloodstream infections from contamination of epoetin alfa at a hemodialysis center. N Engl J Med . 2001 May 17. 344(20):1491-7. [QxMD MEDLINE Link] .

Ursua PR, Unzaga MJ, Melero P, et al. Serratia rubidaea as an invasive pathogen. J Clin Microbiol . 1996 Jan. 34(1):216-7. [QxMD MEDLINE Link] .

Julie G, Julie C, Anne G, Bernard F, Philippe V, Madeleine C, et al. Childhood delayed septic arthritis of the knee caused by Serratia fonticola. Knee . 2009 Dec. 16(6):512-4. [QxMD MEDLINE Link] .

Elahian F, Moghimi B, Dinmohammadi F, Ghamghami M, Hamidi M, Mirzaei SA. The anticancer agent prodigiosin is not a multidrug resistance protein substrate. DNA Cell Biol . 2013 Mar. 32(3):90-7. [QxMD MEDLINE Link] . [Full Text] .

Petersen LM, Tisa LS. Friend or foe? A review of the mechanisms that drive Serratia towards diverse lifestyles. Can J Microbiol . 2013 Sep. 59(9):627-40. [QxMD MEDLINE Link] .

Anonymous. The miracle microbe: Serratia marcescens. [Full Text] .

Yu VL. Serratia marcescens: historical perspective and clinical review. N Engl J Med . 1979 Apr 19. 300(16):887-93. [QxMD MEDLINE Link] .

Pérez-Tomás R, Viñas M. New insights on the antitumoral properties of prodiginines. Curr Med Chem . 2010. 17(21):2222-31. [QxMD MEDLINE Link] .

Chang CC, Chen WC, Ho TF, Wu HS, Wei YH. Development of natural anti-tumor drugs by microorganisms. J Biosci Bioeng . 2011 May. 111(5):501-11. [QxMD MEDLINE Link] .

Genes C, Baquero E, Echeverri F, Maya JD, Triana O. Mitochondrial dysfunction in Trypanosoma cruzi: the role of Serratia marcescens prodigiosin in the alternative treatment of Chagas disease. Parasit Vectors . 2011 May 6. 4:66. [QxMD MEDLINE Link] . [Full Text] .

Remuzgo-Martínez S, Aranzamendi-Zaldunbide M, Pilares-Ortega L, Icardo JM, Acosta F, Martínez-Martínez L, et al. Interaction of macrophages with a cytotoxic Serratia liquefaciens human isolate. Microbes Infect . 2013 Jun. 15(6-7):480-90. [QxMD MEDLINE Link] .

Gupta N, Hocevar SN, Moulton-Meissner HA, Stevens KM, McIntyre MG, Jensen B, et al. Outbreak of Serratia marcescens Bloodstream Infections in Patients Receiving Parenteral Nutrition Prepared by a Compounding Pharmacy. Clin Infect Dis . 2014 Apr 11. [QxMD MEDLINE Link] .

Ersoz G, Uguz M, Aslan G, Horasan ES, Kaya A. Outbreak of meningitis due to Serratia marcescens after spinal anaesthesia. J Hosp Infect . 2014 Jun. 87(2):122-5. [QxMD MEDLINE Link] .

Engel HJ, Collignon PJ, Whiting PT, Kennedy KJ. Serratia sp. bacteremia in Canberra, Australia: a population-based study over 10 years. Eur J Clin Microbiol Infect Dis . 2009 Jul. 28(7):821-4. [QxMD MEDLINE Link] .

Samonis G, Vouloumanou EK, Christofaki M, Dimopoulou D, Maraki S, Triantafyllou E, et al. Serratia infections in a general hospital: characteristics and outcomes. Eur J Clin Microbiol Infect Dis . 2011 May. 30(5):653-60. [QxMD MEDLINE Link] .

Jones RN. Microbial etiologies of hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia. Clin Infect Dis . 2010 Aug 1. 51 Suppl 1:S81-7. [QxMD MEDLINE Link] .

Posluszny JA Jr, Conrad P, Halerz M, Shankar R, Gamelli RL. Surgical burn wound infections and their clinical implications. J Burn Care Res . 2011 Mar-Apr. 32(2):324-33. [QxMD MEDLINE Link] . [Full Text] .

Rastogi V, Purohit P, Peters BP, et al. Pulmonary infection with serratia marcescens. Indian J Med Microbiol . 2002 Jul-Sep. 20(3):167-8. [QxMD MEDLINE Link] .

Zarogoulidis P, Porpodis K, Konoglou M, Saroglou M, Mitrakas A, Matthaios D, et al. Serratia pneumonia presenting as hemoptysis in a patient with sarcoidosis: a case report. Int J Gen Med . 2011. 4:661-4. [QxMD MEDLINE Link] . [Full Text] .

Wu YM, Hsu PC, Yang CC, Chang HJ, Ye JJ, Huang CT, et al. Serratia marcescens meningitis: Epidemiology, prognostic factors and treatment outcomes. J Microbiol Immunol Infect . 2012 Aug 24. [QxMD MEDLINE Link] .

Hiremath S, Biyani M. Technique survival with Serratia peritonitis. Adv Perit Dial . 2006. 22:73-6. [QxMD MEDLINE Link] .

Friend JC, Hilligoss DM, Marquesen M, Ulrick J, Estwick T, Turner ML, et al. Skin ulcers and disseminated abscesses are characteristic of Serratia marcescens infection in older patients with chronic granulomatous disease. J Allergy Clin Immunol . 2009 Jul. 124(1):164-6. [QxMD MEDLINE Link] . [Full Text] .

al Hazzaa SA, Tabbara KF, Gammon JA. Pink hypopyon: a sign of Serratia marcescens endophthalmitis. Br J Ophthalmol . 1992 Dec. 76(12):764-5. [QxMD MEDLINE Link] .

Faro J, Katz A, Berens P, Ross PJ. Premature termination of nursing secondary to Serratia marcescens breast pump contamination. Obstet Gynecol . 2011 Feb. 117(2 Pt 2):485-6. [QxMD MEDLINE Link] .

Jones J, Crete J, Neumeier R. A case report of pink breast milk. J Obstet Gynecol Neonatal Nurs . 2014 Sep. 43(5):625-30. [QxMD MEDLINE Link] .

Ostrowsky BE, Whitener C, Bredenberg HK, et al. Serratia marcescens bacteremia traced to an infused narcotic. N Engl J Med . 2002 May 16. 346(20):1529-37. [QxMD MEDLINE Link] .

Sunenshine RH, Tan ET, Terashita DM, et al. A multistate outbreak of Serratia marcescens bloodstream infection associated with contaminated intravenous magnesium sulfate from a compounding pharmacy. Clin Infect Dis . 2007 Sep 1. 45(5):527-33. [QxMD MEDLINE Link] .

Horcajada JP, Martinez JA, Alcon A, et al. Acquisition of multidrug-resistant Serratia marcescens by critically ill patients who consumed tap water during receipt of oral medication. Infect Control Hosp Epidemiol . 2006 Jul. 27(7):774-7. [QxMD MEDLINE Link] .

Mills J, Drew D. Serratia marcescens endocarditis: a regional illness associated with intravenous drug abuse. Ann Intern Med . 1976 Jan. 84(1):29-35. [QxMD MEDLINE Link] .

Pinna A, Usai D, Sechi LA, Carta A, Zanetti S. Detection of virulence factors in Serratia strains isolated from contact lens-associated corneal ulcers. Acta Ophthalmol . 2011 Jun. 89(4):382-7. [QxMD MEDLINE Link] .

Friedman ND, Peterson NB, Sumner WT, et al. Spontaneous dermal abscesses and ulcers as a result of Serratia marcescens. J Am Acad Dermatol . 2003 Aug. 49(2 Suppl Case Reports):S193-4. [QxMD MEDLINE Link] .

Mlynarczyk A, Mlynarczyk G, Pupek J, et al. Serratia marcescens isolated in 2005 from clinical specimens from patients with diminished immunity. Transplant Proc . 2007 Nov. 39(9):2879-82. [QxMD MEDLINE Link] .

Bertrand X, Dowzicky MJ. Antimicrobial susceptibility among gram-negative isolates collected from intensive care units in North America, Europe, the Asia-Pacific Rim, Latin America, the Middle East, and Africa between 2004 and 2009 as part of the Tigecycline Evaluation and Surveillance Trial. Clin Ther . 2012 Jan. 34(1):124-37. [QxMD MEDLINE Link] .

Sader HS, Farrell DJ, Flamm RK, Jones RN. Antimicrobial susceptibility of Gram-negative organisms isolated from patients hospitalized in intensive care units in United States and European hospitals (2009-2011). Diagn Microbiol Infect Dis . 2014 Apr. 78(4):443-8. [QxMD MEDLINE Link] .

Tamma PD, Girdwood SC, Gopaul R, Tekle T, Roberts AA, Harris AD, et al. The use of cefepime for treating AmpC ß-lactamase-producing Enterobacteriaceae. Clin Infect Dis . 2013 Sep. 57(6):781-8. [QxMD MEDLINE Link] .

Harris PN, Wei JY, Shen AW, Abdile AA, Paynter S, Huxley RR, et al. Carbapenems versus alternative antibiotics for the treatment of bloodstream infections caused by Enterobacter, Citrobacter or Serratia species: a systematic review with meta-analysis. J Antimicrob Chemother . 2016 Feb. 71 (2):296-306. [QxMD MEDLINE Link] .

Curtis L. Handwashing and other environmental controls needed to prevent hospital-acquired serratia infections. J Chemother . 2009 Aug. 21(4):470. [QxMD MEDLINE Link] .

de Vries JJ, Baas WH, van der Ploeg K, et al. Outbreak of Serratia marcescens colonization and infection traced to a healthcare worker with long-term carriage on the hands. Infect Control Hosp Epidemiol . 2006 Nov. 27(11):1153-8. [QxMD MEDLINE Link] .

Contributor Information and Disclosures

Payal K Patel, MD, MPH Infectious Disease Physician, Systemwide Medical Director of Antimicrobial Stewardship, Intermountain Health Payal K Patel, MD, MPH is a member of the following medical societies: American College of Physicians , HIV Medicine Association , Infectious Diseases Society of America , Society for Healthcare Epidemiology of America , Society of Hospital Medicine , Washtenaw County Medical Society Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference Disclosure: Received salary from Medscape for employment. for: Medscape.

John L Brusch, MD, FACP Corresponding Faculty Member, Harvard Medical School John L Brusch, MD, FACP is a member of the following medical societies: American College of Physicians , Infectious Diseases Society of America Disclosure: Nothing to disclose.

Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center; Master of the American College of Physicians; Fellow, Infectious Diseases Society of America; Fellow of the Royal College of Physicians, London Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha , American College of Physicians , American Medical Association , Association of Professors of Medicine , Infectious Diseases Society of America , Oklahoma State Medical Association , Southern Society for Clinical Investigation Disclosure: Nothing to disclose.

Thomas E Herchline, MD Professor of Medicine, Wright State University, Boonshoft School of Medicine; Medical Consultant, Public Health, Dayton and Montgomery County (Ohio) Tuberculosis Clinic Thomas E Herchline, MD is a member of the following medical societies: Alpha Omega Alpha , Infectious Diseases Society of America , Infectious Diseases Society of Ohio Disclosure: Received research grant from: Regeneron.

Basilio J Anía, MD Associate Professor of Infectious Diseases, Universidad de Las Palmas de Gran Canaria; Consultant in Internal Medicine, Hospital Universitario Dr. Negrín, Spain Disclosure: Nothing to disclose.

Antonette B Climaco, MD Attending Physician, Division of Infectious Diseases, Department of Medicine, Einstein Healthcare Network Antonette B Climaco, MD is a member of the following medical societies: American Academy of HIV Medicine , HIV Medicine Association , Infectious Diseases Society of America , Philippine Medical Association Disclosure: Nothing to disclose.

Prithiv J Prasad, MBBS Resident Physician, Department of Internal Medicine, Albert Einstein Medical Center Disclosure: Nothing to disclose.

What would you like to print?

• Print this section
• Print the entire contents of
• Print the entire contents of article

• Folliculitis Organism-Specific Therapy
• Proteus Infections
• Infections in the Immunocompromised Host
• Tobramycin Level
• Gram-Negative Folliculitis
• Chronic Granulomatous Disease
• Pyoderma Gangrenosum in a Patient With Dubowitz Syndrome
• Blue Light Therapy in the Management of Chronic Wounds

• Drug Interaction Checker
• Pill Identifier
• Calculators
• 2002228495-overviewDiseases & Conditions Diseases & Conditions Serratia

• 20022012509-overviewDiseases & Conditions Diseases & Conditions Folliculitis Organism-Specific Therapy

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Infect Drug Resist

Molecular Characterization of Carbapenem-Resistant Serratia marcescens Clinical Isolates in a Tertiary Hospital in Hangzhou, China

1 Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou City, Zhejiang Province, 310016, People’s Republic of China

2 Clinical Laboratory, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou City, Zhejiang Province, 310016, People’s Republic of China

Introduction

Although carbapenem-resistant Enterobacteriaceae (CRE) have been thoroughly investigated as the pathogens most commonly associated with clinical infections, data on Serratia marcescens are inadequate and superficial.

In this study, we characterized 36 carbapenem-resistant Serratia marcescens (CRSM) isolates in our hospital from April 2018 to March 2019 by analysing whole-genome sequencing (WGS) data. The molecular typing of the isolates was performed using both pulsed-field gel electrophoresis (PFGE) and core genome multilocus sequence typing (cgMLST).

Thirty-three of the 36 isolates showed carbapenem resistance conferred by a bla KPC-2 -harbouring plasmid, while the remaining three isolates were characterized by overexpression of beta-lactamase combined with porin loss. The bla KPC-2 genes in all the isolates were located on a plasmid of ~103 kb, except one, which was on a plasmid of ~94 kb. The gene structure surrounding bla KPC-2 in the plasmids was confirmed by integration of a partial Tn4401 structure and an intact IS26 as previously reported. Most of the plasmids also contained a mobile genetic element (MGE) comprising qnr and ISKpn19, which provided evidence of horizontal transfer of antibiotic resistance genes.

The thirty-six CRSM isolates were mainly clonally disseminated with a bla KPC-2 -harbouring plasmid in our hospital. The gene structure surrounding bla KPC-2 as an MGE, as well as the qnr segment, might be acquired by horizontal gene transfer, and it could aggravate the infection and increase the difficulty of clinical treatment.

Carbapenem-resistant Enterobacteriaceae are a major class of bacterial pathogens globally, but studies have focused on the organisms most commonly associated with clinical infections in the United States: Klebsiella spp., Enterobacter spp., and Escherichia co l i. 1 , 2 A report from the United States in 2014–2017 described Serratia marcescens as a less commonly encountered species that could also show carbapenem resistance by harbouring carbapenem resistance genes such as bla KPC-2 and bla VIM . 3 Similarly, in China, little attention has been paid to S. marcescens , as it is not often encountered in clinical infection. S. marcescens has intrinsic resistance to ampicillin and cephalosporins but not to carbapenems. 4 However, carbapenem-resistant S. marcescens (CRSM) was found harbouring a plasmid-mediated Klebsiella pneumoniae carbapenemase (KPC), which potentially increased the complexity of clinical infections in China in 2007. 5 , 6

As a member of Enterobacteriaceae that was first described in 1819, S. marcescens is a gram-negative bacillus and was initially considered a non-pathogenic organism for years. It is characterized by red pigmentation, and the function of this red pigment (prodigiosin) remains unclear because clinical isolates are rarely pigmented. 7 In the 19th century, this species was used as a tracer organism and as a biological warfare test agent in the military and was studied in medical experiments. 8 However, as reports of clinical infections have emerged and increased, S. marcescens is now thought to be an opportunistic pathogen. 9 It is an important cause of every conceivable kind of infection, including respiratory tract infection, urinary tract infection (UTI), septicaemia, meningitis, conjunctivitis, endocarditis and wound infections. 10 – 16 Although S. marcescens displayed relatively low virulence, it caused nosocomial infections in immunocompromised patients, both adults and neonates. 17 , 18

S. marcescens often shows carbapenem resistance conferred by bla KPC -harbouring plasmids of different types. 5 , 19 , 20 As a result of the resistance of S. marcescens to most beta-lactams, clonal dissemination is aggravated, and the difficulty of clinical treatment increases. In this study, we investigated the clonal dissemination and resistance mechanism of 36 non-duplicated CRSM isolates in our hospital between April 2018 and March 2019. The whole-genome sequencing (WGS) method was used for molecular typing of isolates, which was rarely performed before analysing the structure of carbapenemase-producing plasmids. We aimed to clarify the dissemination and carbapenem resistance mechanism of S. marcescens in our hospital, which may contribute to clinical treatment and monitoring for infection control.

Materials and Methods

Isolate collection.

Thirty-six CRSM isolates were collected from 36 different patients in Sir Run Run Shaw Hospital, Hangzhou, from April 2018 to March 2019. Species identification was performed by MALDI-TOF mass spectrometry. All CRSM isolates were collected from various wards, including the Department of General Surgery (n=29), ICUs (n=4), the Department of Infectious Diseases (n=1), the Department of Cardiology (n=1), and the Department of Head and Neck Surgery (n=1). Three kinds of specimens were collected, namely, body fluid (n=29), sputum (n=5) and blood (n=2). Most patients were exposed to broad-spectrum antibiotics before the isolate was collected. All isolates were obtained more than 2 days after the patients were admitted to the hospital.

Antimicrobial Susceptibility Testing

The minimal inhibitory concentrations (MICs) of the CRSM isolates were determined by the broth microdilution method. Carbapenem resistance was defined as resistance to any carbapenems, including meropenem, imipenem and ertapenem, in accordance with 2019 Clinical and Laboratory Standards Institute (CLSI) guidelines. 4 The susceptibility of tigecycline was determined according to US Food and Drug Administration breakpoints for Enterobacteriaceae. Escherichia coli ATCC 25922 was used as a quality control strain. The efflux pump inhibitor test was performed as a broth microdilution experiment with or without the inhibitors in combination with meropenem. 21

Pulsed-Field Gel Electrophoresis (PFGE)

Genomic DNA was prepared as described previously with some modifications. 22 Isolated colonies were harvested from Mueller-Hinton agar plates after overnight incubation at 37°C, and the suspension was adjusted to a concentration of 10 9 CFU/mL in cell suspension buffer (100 mM Tris-HCl, 100 mM EDTA, pH=8). After a short incubation of approximately 5–10 mins at 37°C, the bacterial suspension was mixed with an equal volume of 1% Gold Agarose (Lonza, USA) and allowed to solidify in a 100-µL plug mould. The DNA block was incubated overnight at 54°C in 1 mL of cell lysis buffer (50 mM Tris-HCl, 50 mM EDTA, 1% sarcosyl, 100 µg/mL proteinase K, pH=8). To eliminate the lysed bacterial material and inactivate proteinase K activity, the DNA blocks were washed four times at 50°C in 4 mL of Tris-EDTA buffer (100 mM Tris-HCl, 1 mM EDTA, pH=8). A slice of each plug was cut and incubated with SpeI (Takara, Japan). Restriction fragments of DNA were separated by pulsed-field gel electrophoresis (PFGE) with a CHEF MAPPER apparatus (Bio-Rad, USA) through 1% Gold Agarose. Electrophoresis was performed at 6 V/cm and 14°C. The run time was 18 h, with the pulse time ramping from 5 to 60 s. XbaI-digested DNA of Salmonella enterica serotype Braenderup H9812 was electrophoresed as the size marker.

Whole Genome Sequencing (WGS) and Resistance Gene Analysis

Thirty-six CRSM isolates were cultured overnight in Mueller-Hinton broth at 37°C for genomic DNA extraction using the QIAamp DNA Mini Kit (QIAGEN, Germany). All the genomic DNAs were sequenced using paired-end 500-bp insert libraries on an Illumina HiSeq X Ten, and the resulting 150-bp Illumina reads were assembled using CLC Genomics Workbench with default settings. To obtain complete genome assemblies, five isolates (C110, 1140, 2838, 3024, and 4201) representing five clone clusters in PFGE were sequenced on the Nanopore MinIon platform. Antibiotic resistance genes were identified by resFinder3.2 ( https://cge.cbs.dtu.dk/services/ResFinder/ ) with the default threshold.

Core Genome Multilocus Sequence Typing (cgMLST)

To improve the accuracy of the PFGE typing method, a local core genome multilocus sequence typing (cgMLST) scheme was established following the guide for Ridom SeqSphere+ software ( http://www.ridom.de/seqsphere/tutorials/index.shtml ). A task template of 4847 targets for cgMLST and 400 targets as accessories was established by importing assembly files of all isolates except isolates 3024 and 4201. Then, all assembly files of the 36 isolates were imported into the created database, and a comparison table was generated. Finally, a minimum spanning tree was generated by ignoring missing values.

Conjugation Experiment

After incubation for 4–6 h, NaN 3 -resistant E. coli J53 was used as the recipient strain (100 µL) mixed with the recipient strain (100 µL), and filter mating was performed for 16–18 h at 37°C. Then, the mixture on the filter membrane was inoculated into plates containing NaN 3 (300 µg/mL, Sangon, China) supplemented with ampicillin (100 µg/mL, Sangon, China) for 24 h at 37°C. The colonies that grew on the selection plates were picked and identified by PCR and MALDI-TOF mass spectrometry.

Analysis of the Genetic Structure Surrounding bla KPC-2

The related bla KPC-2 -harbouring plasmids were identified by BLAST in NCBI ( https://blast.ncbi.nlm.nih.gov/Blast.cgi ). The open reading frames (ORFs) were predicted by the RAST system ( http://rast.nmpdr.org/ ). The mobile genetic elements (MGEs) were determined by ISfinder ( https://www-is.biotoul.fr/blast.php ), and figures were drawn with CLC Genomics Workbench. The sequencing data for the 36 isolates have been deposited at DDBJ/ENA/GenBank under the accession numbers {"type":"entrez-nucleotide","attrs":{"text":"WUUW00000000","term_id":"1790135298","term_text":"WUUW00000000"}} WUUW00000000 - {"type":"entrez-nucleotide","attrs":{"text":"WUWF00000000","term_id":"1790135500","term_text":"WUWF00000000"}} WUWF00000000 and {"type":"entrez-nucleotide-range","attrs":{"text":"CP047679-CP047693","start_term":"CP047679","end_term":"CP047693","start_term_id":"1799038663","end_term_id":"1799064056"}} CP047679-CP047693 .

Dissemination and Distribution of CRSM

There were a total of 36 nonduplicated CRSM isolates collected from our hospital from April 2018 to March 2019. All isolates were divided into 5 clusters by the PFGE typing method and named from cluster A to cluster E ( Figure 1A ). Thirty-four of the 36 CRSM isolates were divided into clusters A, B and C with similarity values of 94.167%, 81.807% and 92.327%, respectively. There was only one isolate each in cluster D (isolate 3024) and cluster E (isolate 4201), and the similarity values of isolates 3024 and 4201 were significantly lower than those of the other three clusters. As seen in the minimum spanning tree generated by a local cgMLST scheme ( Figure 1B ), isolate 3024 (in green) and especially isolate 4201 (in purple) were quite distant from the other isolates, as predicted by the PFGE typing method. In addition, 4 isolates (in red box) differed from isolates C83 and C91 (in red) with no less than 14 allelic genes, similar to isolate 3024. Furthermore, the collection times of all isolates could be divided into 5 periods, which corresponded to the 5 clusters.

The Molecular typing of 36 carbapenem-resistant Serratia marcescens (CRSM) isolates by two methods. ( A ). Pulsed-field gel electrophoresis (PFGE) typing. The isolates were divided into 5 cluster types including cluster A, B, C, D and E based on the cutoff values. ( B ). The local ad hoc scheme of Core genome multilocus sequence typing (cgMLST). Isolates with no less than 14 different allelic genes were identified as follows: C60, 3717, 3460 and 3725 (in red boxes), 3024 (in green), 4201 (in purple).

Upon additionally considering clinical information, 33 of the 36 isolates from the same clone were collected from the Department of General Surgery and ICU, which were the main regions of clonal dissemination and distribution. Notably, the isolate with the most significant difference in molecular typing, isolate 4201, was derived from a patient once transferred from the Department of Cardiac Surgery to the ICU after valve replacement surgery. Since it was the only case found in the ICU, we suggest that it was a special clone type that originated from the Department of Cardiac Surgery.

Antibiotic Resistance Mechanism of CRSM

All 36 CRSM isolates were highly resistant to carbapenems, including meropenem, imipenem and ertapenem, but were almost susceptible to amikacin and especially tigecycline ( Table 1 ). PCR and a modified carbapenem inactivation method (mCIM) 4 revealed that 33 of the 36 CRSM isolates were KPC-producing isolates. The WGS data were used to investigate the diversity of the antibiotic resistance genes carried by the 36 CRSM isolates ( Table 2 ). It was demonstrated that bla KPC-2 was the only carbapenemase gene in 33 of the isolates. In 3 carbapenem-resistant isolates without any carbapenemase genes, the outer membrane proteins ompF and ompC were not detected, while the beta-lactamases SRT-1 and CTX-M-14 were overexpressed ( Supplementary Figure S1 ). Moreover, the efflux pump inhibitor test based on antimicrobial susceptibility testing was performed for the 36 isolates. This test demonstrated that the MICs of meropenem for most of the isolates decreased by one- or two-fold after the inhibitor was added.

The MIC Distribution of 36 CRSM

Abbreviations: CRSM, carbapenem-resistant Serratia marcescens , MIC, minimum inhibitory concentration; MEM, meropenem; IPM, imipenem; ETP, ertapenem; CAZ, ceftazidime; FOX, cefoxitin; CTX, cefotaxime; FEP, cefepime; ATM, aztreonam; CIP, ciprofloxacin; AK, amikacin; TGC, tigecycline; CAV/AVI, ceftazidime avibactam.

The Distribution of Antibiotic Resistance Genes in 36 CRSM Isolates

Abbreviations: CRSM, carbapenem-resistant Serratia marcescens , P, plasmid; C, chromosome.

Resistance to carbapenems was successfully transferred from 33 bla KPC-2 -harbouring isolates to the E.coli J53 recipient, except isolates C112 and 4201, by conjugation experiments. The meropenem, imipenem and ertapenem MICs of the transconjugants were in the range of 1–8 µg/mL, which indicated a slight increase compared to E. coli J53. Meanwhile, all transconjugants remained susceptible to amikacin and tigecycline ( Table 3 ). In addition, the transconjugants were also resistant to ceftazidime but remained susceptible to ciprofloxacin (CIP), with a slight increase in the MIC.

Antibiotic Susceptibilities of Transconjugants and E. coli J53

Abbreviations: MIC, minimum inhibitory concentration; MEM, meropenem; IPM, imipenem; ETP, ertapenem; CAZ, ceftazidime; CIP, ciprofloxacin; AK, amikacin; TGC, tigecycline.

General Characteristics of bla KPC-2 -Harbouring Plasmids

The bla KPC-2 gene was found in 33 isolates and localized on an ~78–104 kb plasmid by a S1 Southern blot ( Supplementary Figure S2 ). Long-read sequencing data of five isolates were assembled, and the characteristics of the chromosomes and plasmids are listed in Table 4 . Each isolate contained a large plasmid ( bla KPC-2 harbouring) and a small plasmid (no resistance gene found) in addition to a chromosomal genome with a length of ~5.4 Mbp. The reads were mapped to the reference genome in CLC Genomics Workbench, and 31 bla KPC-2 -harbouring plasmids of the same size had the same sequence as the bla KPC-2 -harbouring plasmid from isolate C110 (subsequently named pC110-KPC), which was 103.167 kb in size. The bla KPC-2 -harbouring plasmids from isolate 3024 and isolate 4201 (subsequently named p3024-KPC and p4201-KPC) had lengths of 103.175 kb and 94.056 kb, respectively.

Characteristics of the Nanopore-Sequenced Genome Assembly of Five CRSM

Abbreviations: CRSM, carbapenem-resistant Serratia marcescens , bp, base pair; ‒, not found by plasmidFinder and resFinder on CGE website.

pC110-KPC was a closed circular DNA with a size of 103167 bp and belonged to incompatibility group F. It contained 138 predicted ORFs with an average G+C content of 54.2%. A BLAST search in NCBI revealed that plasmid pC110-KPC shares high identity with the previously reported IncF plasmids pSZF_KPC (accession no. {"type":"entrez-nucleotide","attrs":{"text":"MH917122.1","term_id":"1496323261","term_text":"MH917122.1"}} MH917122.1 ) 23 and p628-KPC (accession no. {"type":"entrez-nucleotide","attrs":{"text":"KP987218.1","term_id":"918463219","term_text":"KP987218.1"}} KP987218.1 ), 24 both of which were from a K. pneumoniae isolate found in China, with 94% query coverage and >99% nucleotide identity ( Figure 2A ). The bla KPC-2 -harbouring plasmids from isolates 1140 and 2838 were exactly the same as pC110-KPC. Plasmid p3024-KPC was 8 bp longer than pC110-KPC as a result of a short base segment (TATCTTGT) inserted into position 2476–2477 of pC110-KPC. Plasmid p4201-KPC was 94056 bp in length and contained 122 predicted ORFs with an average G+C content of 53.1%. It was similar (95% query coverage and >99% nucleotide identity) to pHS091147 (accession no. {"type":"entrez-nucleotide","attrs":{"text":"KX236178.1","term_id":"1043724674","term_text":"KX236178.1"}} KX236178.1 ) 25 from a K. pneumoniae isolate found in China ( Figure 2B ).

The circular maps of pC110-KPC and p4201-KPC. ( A ). The circle in yellow represented plasmid pC110-KPC, in orange represented pSZF_KPC, in red represented p628-KPC. ( B ). The circle in purple represented p4201-KPC, in blue represented pHS091157. The peak map in ( A ) and ( B ) represented the GC content of plasmid pC110-KPC and p4201-KPC respectively. Arcs in grey indicate the position of bla KPC and bla qnr in plasmids pC110-KPC and p4201-KPC. The maps were created by Brig v0.95.

Genetic Environment of the bla KPC-2 Gene

All bla KPC-2 -harbouring plasmids in this study belonged to the non-Tn4401 structure type, which was defined as bla KPC -bearing non-Tn4401 elements (NTE KPC ) as previously reported. 26 In fact, the surrounding structure of bla KPC-2 was considered to result from the integration of a partial Tn 4401 structure and an intact IS 26 . The ORFs are ordered as follows ( Figure 3 ): IS 26 , Tn 3 -resolvase, IS Kpn27 , the bla KPC-2 gene, and the IS Kpn6 -like element. This structure was the same as that in plasmid pKPHS2 (accession no. {"type":"entrez-nucleotide","attrs":{"text":"CP003224","term_id":"365803828","term_text":"CP003224"}} CP003224 ), 27 except for a point mutation (C→T) ( Figure 3 ). Plasmid pKPHS2 was from a K. pneumoniae isolate and had a similar backbone as another K. pneumoniae plasmid, pKP048 (accession no. {"type":"entrez-nucleotide","attrs":{"text":"FJ628167","term_id":"299474760","term_text":"FJ628167"}} FJ628167 ), 28 and both of these plasmids were found in China. The surrounding structure of bla KPC-2 in plasmid pKP048 lacked IS 26 with an incomplete tnpR gene compared to plasmid pC110-KPC, which we considered to be a result of gene recombination.

A schematic diagram of the genetic structure surrounding bla KPC-2 . The genetic structure surrounding bla KPC-2 in the plasmid pC110-KPC represented all plasmids harbouring bla KPC-2 in this study. The positions indicated by orange lines are the point mutation positions at which C and T are in plasmids pC110-KPC and pKPHS2, respectively. The direction of the arrow represents the direction of transcription.

Coexistence of the Quinolone Resistance Gene qnrS1 with bla KPC-2

Other types of resistance genes were identified from the genome sequences, including bla CTX-M-14 , bla SRT-1 (bla SST-1 ), qnrS1 (qnrD1), aac(3)-IId, aac(6ʹ)-Ic, and tet(41) , among which qnrS1 was the only resistance gene located on a bla KPC-2 -harbouring plasmid ( Table 2 ). There was an ~6-kb region comprising a quinolone resistance gene ( qnrS1 ) and an intact ISKpn19 ~8 kb downstream of bla KPC-2 on plasmids ( Figure S3 ). In addition, gene qnrS1 was also located in the chromosome of most isolates.

Carbapenem-resistant S. marcescens strains are distributed and disseminated globally, and the positivity rate has increased since China has been the epidemic region for carbapenem-resistant Enterobacteriaceae (CRE). Several studies on the clonal dissemination of S. marcescens were previously reported. 17 , 29 , 30 However, this was the first study that utilized WGS to gain insight into antibiotic resistance genes and MGEs in CRSM isolated from different patients in China.

WGS has emerged as an ultimate typing tool suitable for any bacterial species, study type, and laboratory. 31 cgMLST has been proposed as a very useful and practical method based on WGS to distinguish isolates within epidemic settings and between epidemic and unrelated specimens. 32 As there was no public database of cgMLST for S. marcescens , we established a local cgMLST scheme using Ridom SeqSphere software. By cgMLST, four isolates were distinguished from PFGE typing. The results of cgMLST differed from those of PFGE typing, which improved the accuracy of molecular typing and was attributed to the high sensitivity of cgMLST.

It was reported 33 that the mechanisms of beta-lactam resistance in S. marcescens include the production of beta-lactamases, diminished outer membrane permeability, modification of the target penicillin-binding proteins (PBPs), overexpression of active efflux systems, synthesis of aminoglycoside-modifying enzymes, and structural alteration of the GyrA protein. The mechanism of carbapenem resistance in the CRSM isolates was divided into four types: 34 carbapenemase production, functional efflux pump systems, diminished permeability of the outer membrane and alteration of PBP targets. Since carbapenemase production was the dominant type referred to in most in related reports, 29 , 30 , 35 KPC production was the most frequent type observed in our study. The resistance mechanism of the efflux pump in 3 isolates without bla KPC-2 did not play the main role. In addition, we also evaluated the outer membrane porins (ompF and ompC), which are related to antimicrobial resistance. Based on the results ( Figure S1 ) and a previous report, 36 it was suggested that the carbapenem resistance of the 3 isolates without bla KPC-2 was predominantly mediated by the overexpression of SRT-1 and CTX-M-14 combined with porin loss.

In China, S. marcescens -harboured bla KPC-2 was first described on a conjugative plasmid in 2007, and since then, related reports have emerged. The sizes of plasmids harbouring bla KPC-2 in S. marcescens varied from 50 kb to 118 kb, and the plasmid types were IncF, IncK, IncL/M and IncX, most of which were conjugative. 19 , 20 , 23 , 29 In this study, we found that most of the plasmids were ~103 kb in length and belonged to the IncF incompatibility group, which was not previously reported. Through WGS analysis against the NCBI database, we hypothesized that all of the plasmids were derived from K. pneumoniae isolates in China. All of the bla KPC-2 -harbouring plasmids were successfully transferred except plasmids from isolates C112 and 4201. The carbapenem MICs of the transconjugants increased but not significantly, probably because of the low copy numbers of the plasmids. The slight increase in the CIP MIC was due to the qnrS gene carried by the bla KPC-2 -harbouring plasmids.

Since bla KPC-2 could be transferred frequently either by plasmids or by integrative and conjugative elements (ICEs) and insertion elements (ISs), confirming the genetic structure surrounding bla KPC-2 can contribute to monitoring the horizontal transfer of bla KPC-2 and the evolution process of bla KPC-2 -harbouring plasmids. The most common bla KPC-2 -containing mobile element is a Tn 3 -based transposon, Tn 4401 . All CRSM isolates harbouring bla KPC-2 in this study possessed the same structure surrounding the bla KPC-2 gene as pC110-KPC, as shown in Figure 3 . This structure was defined as the NTE KPC -Ib group, which was represented by plasmid pKPHS2. 26 There was only one base difference between pC110-KPC and pKPHS2. Based on the timeline, it was suggested that the former was probably derived from the latter by point mutation.

As WGS showed, qnrS1 was the only resistance gene located on the bla KPC-2 -harbouring plasmids. The qnrS1 -harbouring segment was widely distributed in plasmids from K. pneumoniae ; however, this segment did not occur in plasmid p4201-KPC or in plasmids pSZF_KPC and p628-KPC. The combination of the similar genes qnrS1 and IS Kpn19 was also found in E. coli as previously reported. 37 It was indicated that the segment could have been transferred among bla KPC-2 -harbouring plasmids and chromosomes from different strains, and this was probably the way the multi-resistant plasmid evolved.

All isolates collected in this study were confirmed to be resistant to most beta-lactams, including carbapenems, but were susceptible to tigecycline and amikacin ( Table 1 ). Although most of the patients with CRSM could not be clearly diagnosed with infection or colonization by CRSM because of the complex clinical situation, they recovered after administration of tigecycline and amikacin, which were often combined with beta-lactams. Furthermore, all isolates were susceptible to ceftazidime avibactam (CAZ/AVI), as determined by the broth microdilution method, which provides a strong possibility of combination therapy as previously reported. 38 , 39

Characterization of the dissemination and carbapenem resistance mechanism of S. marcescens in our hospital showed that there were still some limitations in this study. All isolates were collected from the patients of a single center and none was collected from the ward environment in the hospital, so the sample size was limited for a more detailed investigation. Because a public MLST or cgMLST database has not been established to date, the isolates in our study cannot be officially defined and compared among different laboratories.

In this study, CRSM isolates were mainly clonally disseminated with a bla KPC-2 -harbouring plasmid in a nosocomial environment. The gene structure surrounding bla KPC-2 , as well as the qnr segment, might be acquired by horizontal gene transfer, and it could aggravate the infection and increase the difficulty of clinical treatment. Since MGEs containing carbapenem resistance genes are commonly associated with horizontal gene transfer, further study is required.

Funding Statement

This work was supported by the National Natural Science Foundation of China (grant number 81830069) and the Key Research and Development Programme of Zhejiang (grant number 2015C03046).

Ethics Approval

The collection of CRSM was part of the routine hospital laboratory procedure.

The authors report no conflicts of interest associated with this work.

Serratia marcescens

Relevance of pathogen in transmission in endoscopy, relevance for endoscope processing , transmission route, resistance to antibiotics, sources and further readings.