Burden and Management of Multi-Drug Resistant Organism Infections in Solid Organ Transplant Recipients Across the World: A Narrative Review.

Solid organ transplant (SOT) recipients are particularly susceptible to infections caused by multidrug-resistant organisms (MDRO) and are often the first to be affected by an emerging resistant pathogen. Unfortunately, their prevalence and impact on morbidity and mortality according to the type of graft is not systematically reported from high-as well as from low and middle-income countries (HIC and LMIC). Thus, epidemiology on MDRO in SOT recipients could be subjected to reporting bias. In addition, screening practices and diagnostic resources may vary between countries, as well as the availability of new drugs. In this review, we aimed to depict the burden of main Gram-negative MDRO in SOT patients across HIC and LMIC and to provide an overview of current diagnostic and therapeutic resources.

Survey on the approach to antibiotic prophylaxis in liver and kidney transplant recipients colonized with "difficult to treat" Gram-negative bacteria.

BACKGROUND: Performance of active screening for multidrug-resistant Gram-negative bacteria (MDR-GNB) and administration of targeted antibiotic prophylaxis (TAP) in colonized patients undergoing liver (LT) and/or kidney transplantation (KT) are controversial issues. METHODS: Self-administered electronic cross-sectional survey disseminated from January to February 2022. Questionnaire consisted of four parts: hospital/transplant program characteristics, standard screening and antibiotic prophylaxis, clinical vignettes asking for TAP in patients undergoing LT and KT with prior infection/colonization with four different MDR-GNB (extended-spectrum cephalosporin-resistant Enterobacterales [ESCR-E], carbapenem-resistant Enterobacterales [CRE], multidrug-resistant Pseudomonas aeruginosa [MDR-Pa], and carbapenem-resistant Acinetobacter baumannii [CRAb]). RESULTS: Fifty-five respondents participated from 14 countries, mostly infectious disease specialists (69%) with active transplant programs (>100 procedures/year for 34.5% KT and 23.6% LT), and heterogeneous local MDR-GNB prevalence from <15% (30.9%), 15%-30% (43.6%) to >30% (16.4%). The frequency of screening for ESCR-E, CRE, MDR-Pa, and CRAb was 22%, 54%, 17%, and 24% for LT, respectively, and 18%, 36%, 16%, and 11% for KT. Screening time-points were mainly at transplantation 100%, only one-third following transplantation. Screening was always based on rectal swab cultures (100%); multi-site sampling was reported in 40% of KT and 35% of LT. In LT clinical cases, 84%, 58%, 84%, and 40% of respondents reported TAP for prior infection/colonization with ESCR-E, CRE, MDR-Pa, and CRAb, respectively. In KT clinical cases, 55%, 39%, 87%, and 42% of respondents reported TAP use for prior infection/colonization with ESCR-E, CRE, MDR-Pa, and CRAb, respectively. CONCLUSION: There is a large heterogeneity in screening and management of MDR-GNB carriage in LT and KT.

Meet in the middle: Could cell mediated-immunity assays be the answer for ideal Cytomegalovirus prophylaxis after lung transplantation? Observational study from a single center with intermittent antiviral prophylaxis.

BACKGROUND: Cytomegalovirus (CMV) can cause tissue-invasive disease and indirect effects after lung transplantation (LTx) such as acute rejection episodes and chronic lung allograft dysfunction. Monitoring CMV-specific cell immune recovery (CMV-CIR) after LTx can individualize CMV risks and establish better antiviral approach. This study evaluated the dynamics of CMV-CIR, using QuantiFERON-CMV assay (Qiagen Group), in the first year after LTx. METHODS: Prospective observational cohort study included lung transplant recipients from December/2015 to December/2016. Universal antiviral prophylaxis with intravenous ganciclovir 5 mg/kg/day 3 days/week for 3 months was given for CMV-seropositive recipients (R+) and only CMV-seropositive donor and negative recipient (D+/R-) received a 6-month-prophylaxis with ganciclovir and valganciclovir, on alternate days, in the first 3 months and then, 3 more months of valganciclovir. QuantiFERON-CMV was measured at the same time points of surveillance bronchoscopies. CMV infection was defined as any DNAemia detected and CMV disease with proven biopsy or antigenemia pp65 above 10 cells/300.000 neutrophils. RESULTS: Thirty-eight patients were included. On days 45, 90, and 365 days post-LTx, 60%, 72%, and 81% QuantiFERON-CMV were reactive, respectively. Eleven patients (28.9%) presented CMV-disease and 27 DNAemia/CMV infections. Reactive tests were able to predict CMV disease only at 90 days after LTx (p = .027) but failed on DNAemia/CMV infection (p = .148). Daily prophylaxis, for D+/R- patients (13.2%), remained as an independently associated factor for not achieving reactive QuantiFERON-CMV (adjusted OR .27, 95%CI .12-.60, p = .02). CONCLUSION: QuantiFERON-CMV may be another diagnostic tool to help stratify CMV-disease risk and individualized antiviral prophylaxis after LTx.

Brazilian perspective: antimicrobial stewardship in solid organ transplant.

BACKGROUND: The incidence of multidrug resistant organisms (MDROs) infections among solid organ transplant (SOT) patients is very high in Brazil. METHODS: This review will discuss antimicrobial use and resistance in SOT in Brazil, highlighting the main barriers and facilitators for implementation of an antimicrobial stewardship programme (ASP). RESULTS: The most common group of MDROs is carbapenem-resistant Gram-negative bacteria and vancomycin-resistant Enterococcus. Carbapenem-resistant Enterobacterales (CREs) are the most frequent MDROs and have been reported as donor-derived as well. Although ASPs are mandatory in the country, there is a lack of information regarding ASPs in SOT recipients. The main barriers for the implementation of ASPs in Brazilian hospitals are lack of electronic medical records, absence of national guidelines specific to SOT recipients, lack of recommendations on surveillance culture to evaluate colonization and transmission of donor-derived MDROs, limited availability of rapid diagnostic tests, and insufficient pharmacist and clinician time allocated to ASP activities in some SOT centers. CONCLUSIONS: The incidence of MDRO infections caused mainly by VREs and CREs is very high in the country. There is limited data regarding antimicrobial use among SOT recipients in Brazil. The absence of antimicrobial stewardship national guidelines specific to SOT recipients is one of the main barriers for the implementation of ASPs in Brazilian hospitals.

Prediction models for carbapenem-resistant Enterobacterales carriage at liver transplantation: A multicenter retrospective study.

BACKGROUND: Carbapenem-resistant Enterobacterales (CRE) colonisation at liver transplantation (LT) increases the risk of CRE infection after LT, which impacts on recipients' survival. Colonization status usually becomes evident only near LT. Thus, predictive models can be useful to guide antibiotic prophylaxis in endemic centres. AIMS: This study aimed to identify risk factors for CRE colonisation at LT in order to build a predictive model. METHODS: Retrospective multicentre study including consecutive adult patients who underwent LT, from 2010 to 2019, at two large teaching hospitals. We excluded patients who had CRE infections within 90 days before LT. CRE screening was performed in all patients on the day of LT. Exposure variables were considered within 90 days before LT and included cirrhosis complications, underlying disease, time on the waiting list, MELD and CLIF-SOFA scores, antibiotic use, intensive care unit and hospital stay, and infections. A machine learning model was trained to detect the probability of a patient being colonized with CRE at LT. RESULTS: A total of 1544 patients were analyzed, 116 (7.5%) patients were colonized by CRE at LT. The median time from CRE isolation to LT was 5 days. Use of antibiotics, hepato-renal syndrome, worst CLIF sofa score, and use of beta-lactam/beta-lactamase inhibitor increased the probability of a patient having pre-LT CRE. The proposed algorithm had a sensitivity of 66% and a specificity of 83% with a negative predictive value of 97%. CONCLUSIONS: We created a model able to predict CRE colonization at LT based on easy-to-obtain features that could guide antibiotic prophylaxis.

Increased Risk for Carbapenem-Resistant Enterobacteriaceae Colonization in Intensive Care Units after Hospitalization in Emergency Department.

Carbapenem-resistant Enterobacteriaceae (CRE) colonization is common in hospital patients admitted to intensive care units (ICU) from the emergency department. We evaluated the effect of previous hospitalization in the emergency department on CRE colonization at ICU admission. Our case-control study included 103 cases and 201 controls; cases were patients colonized by CRE at admission to ICU and controls were patients admitted to ICU and not colonized. Risk factors were emergency department stay, use of carbapenem, Simplified Acute Physiology Score, upper digestive endoscopy, and transfer from another hospital. We found that ED stay before ICU admission was associated with CRE colonization at admission to the ICU. Our findings indicate that addressing infection control problems in EDs will help to control carbapenem resistance in ICUs.

Does the urinary tract infection caused by carbapenem-resistant Gram-negative bacilli impact the outcome of kidney transplant recipients?

The incidence of urinary tract infection (UTI) after kidney transplantation (KT) caused by multidrug-resistant (MDR) bacteria is growing. The aim of this study was to analyze the impact of UTI caused by carbapenem-resistant Gram-negative bacteria (CR-GNB) in the survival of graft and recipients following KT. This was a retrospective cohort study involving patients who underwent KT between 2013 and 2016. Patients were followed since the day of the KT until loss of graft, death or end of the follow-up period (31th December 2016). The outcomes measured were UTI by MDR following KT and graft and patient survival. Analyses were performed using Cox regression; for the graft and patient survival analysis, we used a propensity score for UTI by CR-GNB to matching a control group. UTI was diagnosed in 178 (23.9%) of 781 patients, who developed 352 UTI episodes. 44.6% of the UTI cases were caused by MDR bacteria. Identified risk factors for UTI by MDR bacteria were DM, urologic disease as the cause of end-stage renal failure, insertion of ureteral stent, carbapenem use, and delayed graft function (DGF). Risk factors for death during the follow-up period were female gender, patients over 60 years old at the time of KT, DM, body mass index over 31.8, UTI caused by CR-GNB. In conclusion, UTIs caused by CR-GNB have great impact on patients' survival after KT.

Outbreak of IMP-producing carbapenem-resistant Enterobacter gergoviae among kidney transplant recipients.

OBJECTIVES: The objective of this study was to investigate a prolonged outbreak of carbapenem-resistant Enterobacter gergoviae (CREG) involving kidney transplant recipients (KTRs) between 2009 and 2014. METHODS: A case-control study was undertaken. Controls (n = 52) were selected from CREG-negative KTRs. Surveillance cultures for CREG were collected weekly. Colonization was defined as isolation of CREG from surveillance samples or from clinical specimens, with no evidence of infection. We also investigated infection control practices at the facility. RESULTS: Of 26 identified cases, 13 had had no known contact with another CREG-positive patient before the first positive culture. Seven patients (27%) developed infection. The site most often colonized was the urinary tract. During the study period two clusters were identified, one in 2009 and another in 2013-14. DNA sequencing revealed blaIMP-1 in all CREG tested. No environmental or hand cultures tested positive for CREG. An audit of infection control practices detected flaws in the handling and cleaning of urinary tract devices. Multivariate analysis identified advanced age, ureteral stent use, retransplantation and male gender as risk factors for CREG acquisition. CONCLUSIONS: An outbreak among KTRs caused by an unusual species of MDR bacteria may have resulted from a common source of contamination related to urinary tract devices.

Carbapenem-resistant Acinetobacter baumannii acquired before liver transplantation: Impact on recipient outcomes.

Infection with carbapenem-resistant Acinetobacter baumannii (CRAB) after liver transplantation (LT) is associated with high mortality. This study aimed to identify risk factors for post-LT CRAB infection, as well as to evaluate the impact of pre-LT CRAB acquisition on the incidence of post-LT CRAB infection. This was a prospective cohort study of all patients undergoing LT at our facility between October 2009 and October 2011. Surveillance cultures (SCs) were collected immediately before LT and weekly thereafter, until discharge. We analyzed 196 patients who were submitted to 222 LTs. CRAB was identified in 105 (53.6%); 24 (22.9%) of these patients were found to have acquired CRAB before LT, and 85 (81.0%) tested positive on SCs. Post-LT CRAB infection occurred in 56 (28.6%), the most common site being the surgical wound. Multivariate analysis showed that the risk factors for developing CRAB infection were prolonged cold ischemia, post-LT dialysis, LT due to fulminant hepatitis, and pre-LT CRAB acquisition with pre-LT CRAB acquisition showing a considerable trend toward significance (P = 0.06). Among the recipients with CRAB infection, 60-day mortality was 46.4%, significantly higher than among those without (P < 0.001). Mortality risk factors were post-LT infection with multidrug-resistant bacteria, LT performed because of fulminant hepatitis, retransplantation, prolonged cold ischemia, longer LT surgical time, and pre-LT CRAB acquisition, the last showing a trend toward significance (P = 0.08). In conclusion, pre-LT CRAB acquisition appears to increase the risk of post-LT CRAB infection, which has a negative impact on recipient survival. Liver Transplantation 22 615-626 2016 AASLD.

Quantification of C4d deposition and hepatitis C virus RNA in tissue in cases of graft rejection and hepatitis C recurrence after liver transplantation.

Histology is the gold standard for diagnosing acute rejection and hepatitis C recurrence after liver transplantation. However, differential diagnosis between the two can be difficult. We evaluated the role of C4d staining and quantification of hepatitis C virus (HCV) RNA levels in liver tissue. This was a retrospective study of 98 liver biopsy samples divided into four groups by histological diagnosis: acute rejection in patients undergoing liver transplant for hepatitis C (RejHCV+), HCV recurrence in patients undergoing liver transplant for hepatitis C (HCVTx+), acute rejection in patients undergoing liver transplant for reasons other than hepatitis C and chronic hepatitis C not transplanted (HCVTx-). All samples were submitted for immunohistochemical staining for C4d and HCV RNA quantification. Immunoexpression of C4d was observed in the portal vessels and was highest in the HCVTx- group. There was no difference in C4d expression between the RejHCV+ and HCVTx+ groups. However, tissue HCV RNA levels were higher in the HCVTx+ group samples than in the RejHCV+ group samples. Additionally, there was a significant correlation between tissue and serum levels of HCV RNA. The quantification of HCV RNA in liver tissue might prove to be an efficient diagnostic test for the recurrence of HCV infection.

Surgical site infections in liver transplant recipients in the model for end-stage liver disease era: an analysis of the epidemiology, risk factors, and outcomes.

In recipients of liver transplantation (LT), surgical site infection (SSIs) are among the most common types of infection occurring in the first 60 days after LT. In 2007, the Model for End-Stage Liver Disease (MELD) scoring system was adopted as the basis for prioritizing organ allocation. Patients with higher MELD scores are at higher risk for developing SSIs as well as other health care-associated infections. However, there have been no studies comparing the incidence of SSIs in the pre-MELD era with the incidence in the period since its adoption. Therefore, the objectives of this study were to evaluate the incidence, etiology, epidemiology, and outcomes of post-LT SSIs in those 2 periods and to identify risk factors for SSIs. We evaluated all patients who underwent LT over a 10-year period (2002-2011). SSI cases were identified through active surveillance. The primary outcome measure was an SSI during the first 60 days after LT. Risk factors were analyzed via logistic regression, and 60-day survival rates were evaluated via Cox regression. We evaluated 543 patients who underwent LT 597 times. The SSI rates in the 2002-2006 and 2007-2011 periods were 30% and 24%, respectively (P = 0.21). We identified the following risk factors for SSIs: retransplantation, the transfusion of more than 2 U of blood during LT, dialysis, cold ischemia for >400 minutes, and a cytomegalovirus infection. The overall 60-day survival rate was 79%. Risk factors for 60-day mortality were retransplantation, dialysis, and a longer surgical time. The use of the MELD score modified the incidence and epidemiology of SSIs only during the first year after its adoption. Risks for SSIs were related more to intraoperative conditions and intercurrences after LT than to a patient's status before LT.

Genomic analysis and antimicrobial activity of ß-lactam/ß-lactamase inhibitors and other agents against KPC-producing Klebsiella pneumoniae clinical isolates from Brazilian hospitals.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) are highly disseminated worldwide, and isolates co-resistant to other antimicrobial agents pose a threat to effective antimicrobial therapy. Therefore, evaluation of novel antimicrobial drugs is needed to identify potential treatments with better outcomes. We evaluated the in vitro activity of novel antimicrobial drugs/combinations against 97 KPC-producing Klebsiella pneumoniae isolates recovered from different hospitals in Brazil during 2021-2022. Clonality, resistance and virulence genes were detected by whole-genome sequencing. The majority of the isolates (54.6%) were classified as extensively drug resistant or multidrug resistant (44.3%); one isolate showed a pandrug resistance phenotype. The most active antimicrobial agents were meropenem-vaborbactam, cefiderocol, and ceftazidime-avibactam, with sensitivities higher than 90%; resistance to ceftazidime-avibactam was associated with KPC-33 or KPC-44 variants. Colistin and polymyxin B were active against 58.6% of the isolates. The 97 isolates were distributed into 17 different sequence types, with a predominance of ST11 (37.4%). Although high in vitro susceptibility rates were detected for meropenem-vaborbactam and cefiderocol, only ceftazidime-avibactam is currently available in Brazil. Our findings showed limited susceptibility to antimicrobial drugs employed for infection treatment of carbapenem-resistant K. pneumoniae, underscoring the urgent need for stringent policies for antimicrobial stewardship to preserve the activity of such drugs.

Applying mucosal barrier injury laboratory-confirmed bloodstream infection criteria in patients with solid tumors and hematologic malignancies: A retrospective cohort study looking for the real source of infection.

We evaluated the interference of the mucosal barrier injury (MBI) laboratory-confirmed bloodstream infection (MBI-LCBI) criteria on the central-line-associated bloodstream infection (CLABSI) incidence density, and the proportion of catheter-related bloodstream infections (CRBSIs) among those classified as MBI. We detected 339 CLABSIs: 15.0% were classified as MBI-LCBIs, and among these, 19.6% were classified as CRBSIs.

Impact of COVID-19 on healthcare-associated infections: Antimicrobial consumption does not follow antimicrobial resistance.

BACKGROUND: This study aimed to analyze the Healthcare-Associated Infections (HAI) rates and antimicrobial consumption in Intensive Care Units (ICU) in São Paulo city during the COVID-19 pandemic and compare them with the pre-pandemic period. METHODS: This cohort included all hospitals that reported HAI rates (Central-Line-Associated Bloodstream Infection ‒ CLABSI and Ventilator-Associated Pneumonia ‒ VAP), the proportion of microorganisms that caused CLABSI, the proportion of resistant microorganisms, and antimicrobial consumption from January 2017 ‒ December 2020. Hospitals were stratified by the number of beds, Central Venous Catheter (CVC) utilization rate, Mechanical-Ventilation (MV) utilization rate, and type of funding. Statistical analyses were based on time-series plots and regression models. RESULTS: 220 ICUs were included. The authors observed an abrupt increase in CLABSI rates after the pandemic onset. High CLABSI rates during the pandemic were associated with hospital size, funding (public and non-profit private), and low CVC use (≤ 50%). An increase in VAP rates was associated with public hospitals, and high MV use (> 35%). The susceptibility profile of microorganisms did not differ from that of the pre-pandemic period. polymyxin, glycopeptides, and antifungal use increased, especially in COVID-19 ICUs. CONCLUSIONS: HAI increased during COVID-19. The microorganisms' susceptibility profile did not change with the pandemic, but the authors observed a disproportionate increase in large-spectrum antimicrobial drug use.

Genomics and Antimicrobial Susceptibility of Clinical Pseudomonas aeruginosa Isolates from Hospitals in Brazil.

Pseudomonas aeruginosa, an opportunistic pathogen causing infections in immunocompromised patients, usually shows pronounced antimicrobial resistance. In recent years, the frequency of carbapenemases in P. aeruginosa has decreased, which allows use of new beta-lactams/combinations in antimicrobial therapy. Therefore, the in vitro evaluation of these drugs in contemporary isolates is warranted. We evaluated the antimicrobial susceptibility and genomic aspects of 119 clinical P. aeruginosa isolates from 24 different hospitals in Brazil in 2021-2022. Identification was performed via MALDI-TOF-MS, and antimicrobial susceptibility was identified through broth microdilution, gradient tests, or disk diffusion. Whole-genome sequencing was carried out using NextSeq equipment. The most active drug was cefiderocol (100%), followed by ceftazidime-avibactam (94.1%), ceftolozane-tazobactam (92.4%), and imipenem-relebactam (81.5%). Imipenem susceptibility was detected in 59 isolates (49.6%), and the most active aminoglycoside was tobramycin, to which 99 (83.2%) isolates were susceptible. Seventy-one different sequence types (STs) were detected, including twelve new STs described herein. The acquired resistance genes blaCTX-M-2 and blaKPC-2 were identified in ten (8.4%) and two (1.7%) isolates, respectively. Several virulence genes (exoSTUY, toxA, aprA, lasA/B, plcH) were also identified. We found that new antimicrobials are effective against the diverse P. aeruginosa population that has been circulating in Brazilian hospitals in recent years.

Clinical profile and mortality predictors for tuberculosis disease among patients with solid tumours.

BACKGROUND: The characteristics of Mycobacterium tuberculosis (MTb) disease are still obscure in patients with solid tumours, as well as the benefits of screening and treating latent tuberculosis infection (LTBI) in these patients. Our objective was to trace the clinical profile of these individuals and assess the mortality predictors related to tuberculosis (TB). METHODS: We reviewed the medical records of 126 patients with solid tumours malignancy and who developed TB disease between January 2009 and April 2018 at a cancer referral centre. RESULTS: The most common locations of malignancy were head and neck, with squamous cell carcinoma being the most frequent histological type, the majority (97/126) presenting locally invasive tumours (T3 or T4). A total of 120 had TB pulmonary and the microbiological diagnosis was performed in 103/126. The following variables were associated with the risk of death from TB: DPOC lung cancer, BMI, malnutrition, metastasis and ECOG 3 or 4. Previous chemotherapy treatment was a protective factor. CONCLUSIONS: Male, usage of alcohol and smoking were the most predominant patients characteristics in our sample. In the multivariate analysis, lung cancer, presence of metastasis and ECOG ≥ 3 were associated with death from TB.

Frequency and factors associated with hospital readmission after COVID-19 hospitalization: the importance of post-COVID diarrhea.

PURPOSE: The aim of this study was to describe the incidence and risk factors for hospital readmission and infection during the months after COVID-19 hospital admission. METHODS: This prospective study included adult patients who were hospitalized due to COVID-19 and had been discharged from April 2020 to August 2020. All patients had a medical evaluation with a structured questionnaire 6 to 11 months after hospital admission. The authors included only patients with confirmed COVID-19 by RT-PCR. Patients with pregnant/postpartum women, with a proven COVID-19 reinfection or incapable of answering the questionnaire were excluded. RESULTS: A total of 822 patients completed the follow-up assessment, and 68% reported at least one recurrent symptom related to COVID-19. The most frequent symptom was myalgia (42%). Thirty-two percent of patients visited an emergency room after COVID-19 hospitalization, and 80 (10%) patients required re-hospitalization. Risk factors for hospital readmission were orotracheal intubation during COVID-19 hospitalization (p = 0.003, OR = 2.14), Charlson score (p = 0.002, OR = 1.21), congestive heart failure (p = 0.005, OR = 2.34), peripheral artery disease (p = 0.06, OR = 2.06) and persistent diarrhea after COVID-19 hospitalization discharge (p = 0.02, OR = 1.91). The main cause of hospital readmission was an infection, 43 (54%). Pneumonia was the most frequent infection (29%). CONCLUSIONS: The presence of symptoms after six months of COVID-19 diagnosis was frequent, and hospital readmission was relatively high.

Phenotypic and genotypic characteristics of a carbapenem-resistant Serratia marcescens cohort and outbreak: describing an opportunistic pathogen.

Serratia marcescens is an emerging opportunistic pathogen with high genetic diversity. This article describes the microbiological characteristics of isolates and the risk factors for infections caused by carbapenem-resistant S. marcescens. A retrospective study of patients colonized (n=43) and infected (n=20) with carbapenem-resistant S. marcescens over a 3-year period was conducted. Polymerase chain reaction for carbapenemase genes and molecular typing of all available strains was performed. Forty-two isolates were analysed, including three environmental samples identified during an outbreak. Thirty-five carbapenem-resistant S. marcescens carried blaKPC-2, one isolate was blaNDM-positive and four isolates carried blaOXA-101. The genomes were grouped into three clusters with 100% bootstrap; three patterns of mutations on ompC and ompF were found. The strains carried virulence genes related to invasion and haemolysis, and the environmental strains presented fewer mutations on the virulence genes than the clinical strains. Multi-variate analysis showed that previous use of polymyxin (P=0.008) was an independent risk factor for carbapenem-resistant S. marcescens infection. This study highlighted that blaKPC-2 in association with ompC or ompF mutation was the most common mechanism of resistance in the study hospital, and that previous use of polymyxin was an independent risk factor for carbapenem-resistant S. marcescens. There was a predominant clone, including the environmental isolates, suggesting that cross-transmission was involved in the dissemination of this pathogen.