Hidden dissemination of carbapenem-susceptible OXA-48-producing Proteus mirabilis.

OBJECTIVES: To detect a potential hidden dissemination of the blaOXA-48 gene among Proteus mirabilis isolates obtained from a single centre. METHODS: P. mirabilis from diverse clinical samples presenting an ESBL phenotype or obtained from blood cultured from 2017 to 2019 were evaluated. Bacterial identification was performed using MALDI-TOF MS. MICs were determined using International Organization for Standardization (ISO) standard microdilution and interpreted following EUCAST guidelines. WGS was performed using both short- and long-read technologies and assemblies were done using Unicycler. Resistomes were assessed using the ResFinder database. SNPs were detected using the PATRIC bioinformatics platform. Cloning experiments were performed using the pCRII-TOPO cloning kit. RESULTS: Thirty-one out of 108 (28.7%) isolates were positive for blaOXA-48 and blaCTX-M-15. Twenty-nine out of 31 of the isolates were susceptible to temocillin, piperacillin/tazobactam, ertapenem and meropenem, whereas only 2/31 showed a resistance phenotype against these antibiotics. Both blaOXA-48 and blaCTX-M-15 genes were detected within the same chromosomally integrated new transposon in all isolates. The resistant isolates displayed a single mutation located in the putative promoter upstream of blaOXA-48. Cloning experiments confirmed that the mutation was responsible for the resistance phenotype. CONCLUSIONS: The presence of a chromosomal copy of blaOXA-48 did not confer resistance to carbapenems, but a single mutation in the promoter could lead to an increase in resistance. This study shows a hidden circulation of OXA-48-positive, but carbapenem- and piperacillin/tazobactam-susceptible, P. mirabilis isolates that can become resistant to ß-lactams after a single mutation.

A six-month Serratia marcescens outbreak in a Neonatal Intensive Care Unit.

OBJECTIVE: To investigate a Serratia marcescens (S. marcescens) outbreak in a Neonatal Unit in a tertiary university hospital. METHODS: Descriptive study of children admitted to the Unit with S. marcescens infection from November 2012 to March 2013. Conventional microbiological methods for clinical and environmental samples were used. The clonal relationship between all available isolates was established by molecular methods. A multidisciplinary team was formed, and preventive measures were taken. RESULTS: S. marcescens was isolated from 18 children. The overall attack rate was 12%, and the case fatality rate in the Intensive Care Unit was 23.5%. The most prevalent types of infections were pneumonia (6), conjunctivitis (6), and bloodstream infection (5). Clinical isolates and environmental isolates obtained from an incubator belonged to a unique clone. The clonal relationship between all S. marcescens strains helped us to identify the possible source of the outbreak. CONCLUSION: Isolation of S. marcescens from stored water in a container, and from the surface of an incubator after cleaning, suggests a possible environmental source as the outbreak origin, which has been perpetuated due to a failure of cleaning methods in the Unit. The strict hygiene and cleaning measures were the main factors that contributed to the end of the outbreak.

Randomised, double-blind, placebo-controlled, phase 2, superiority trial to demonstrate the effectiveness of faecal microbiota transplantation for selective intestinal decolonisation of patients colonised by carbapenemase-producing Klebsiella pneumoniae (KAPEDIS).

INTRODUCTION: Infections caused by carbapenemase-producing Enterobacterales are frequent and associated with high rates of mortality. Intestinal carriers are at increased risk of infection by these microorganisms. Decolonisation strategies with antibiotics have not obtained conclusive results. Faecal microbiota transplantation (FMT) could be an effective and safe strategy to decolonise intestinal carriers of KPC-producing Klebsiella pneumoniae (KPC-Kp) but this hypothesis needs evaluation in appropriate clinical trials. METHODS AND ANALYSIS: The KAPEDIS trial is a single-centre, randomised, double-blind, placebo-controlled, phase 2, superiority clinical trial of FMT for eradication of intestinal colonisation by KPC-Kp. One hundred and twenty patients with rectal colonisation by KPC-Kp will be randomised 1:1 to receive encapsulated lyophilised FMT or placebo. The primary outcome is KPC-Kp eradication at 30 days. Secondary outcomes are: (1) frequency of adverse events; (2) changes in KPC-Kp relative load within the intestinal microbiota at 7, 30 and 90 days, estimated by real-time quantitative PCR analysis of rectal swab samples and (3) rates of persistent eradication, KPC-Kp infection and crude mortality at 90 days. Participants will be monitored for adverse effects throughout the intervention. ETHICS AND DISSEMINATION: Ethical approval was obtained from Reina Sofía University Hospital Institutional Review Board (approval reference number: 2019-003808-13). Trial results will be published in peer-reviewed journals and disseminated at national and international conferences. TRIAL REGISTRATION NUMBER: NCT04760665.

Multicenter Performance Evaluation of MALDI-TOF MS for Rapid Detection of Carbapenemase Activity in Enterobacterales: The Future of Networking Data Analysis With Online Software.

In this study, we evaluate the performance of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for rapid detection of carbapenemase activity in Enterobacterales in clinical microbiology laboratories during a multicenter networking validation study. The study was divided into three different stages: "software design," "intercenter evaluation," and "clinical validation." First, a standardized procedure with an online software for data analysis was designed. Carbapenem resistance was detected by measuring imipenem hydrolysis and the results were automatically interpreted using the Clover MS data analysis software (Clover BioSoft, Spain). Second, a series of 74 genotypically characterized Enterobacterales (46 carbapenemase-producers and 28 non carbapenemase-producers) were analyzed in 8 international centers to ensure the reproducibility of the method. Finally, the methodology was evaluated independently in all centers during a 2-month period and results were compared with the reference standard for carbapenemase detection used in each center. The overall agreement rate relative to the reference method for carbapenemase resistance detection in clinical samples was 92.5%. The sensitivity was 93.9% and the specificity, 100%. Results were obtained within 60 min and accuracy ranged from 83.3 to 100% among the different centers. Further, our results demonstrate that MALDI-TOF MS is an outstanding tool for rapid detection of carbapenemase activity in Enterobacterales in clinical microbiology laboratories. The use of a simple in-house procedure with online software allows routine screening of carbapenemases in diagnostics, thereby facilitating early and appropriate antimicrobial therapy.