Molecular investigation of an outbreak of multidrug-resistant Acinetobacter baumannii with characterisation of class 1 integrons

We investigated a multidrug-resistant Acinetobacter baumannii outbreak in the Intensive Care Unit (ICU) of a tertiary care hospital in Greece over a 3-month period. Molecular typing of the outbreak isolates from 31 patients revealed that two distinct genotypes were involved. Nine isolates, belonging to both genotypes, were resistant to carbapenems. Samples from the ICU environment and from the hands of personnel were collected to identify possible contamination. Class 1 integrons of 3.1, 2.5 and 2.2 kb were amplified from the clinical and environmental isolates. The 3.1 kb integron carrying five gene cassettes was found for the first time in A. baumannii. The outbreak ceased after implementation of hygienic measures in the ICU, including complete cleaning and disinfection

In vitro bactericidal activity of trimethoprim-sulfamethoxazole alone and in combination with colistin against carbapenem-resistant Acinetobacter baumannii clinical isolates

Trimethoprim-sulfamethoxazole alone and combined with colistin was tested in vitro against six carbapenem-resistant Acinetobacter baumannii (CRAB) clinical strains. After 24 h, at achievable serum concentrations, trimethoprim-sulfamethoxazole effectively killed all strains, while colistin killed only one strain. Trimethoprim-sulfamethoxazole plus colistin rapidly killed all strains after 6 h and for up to 24 h. Trimethoprim-sulfamethoxazole, one of the few remaining antimicrobials that still has a degree of activity, particularly combined with colistin, might represent an effective therapy for severe CRAB infections. Copyright © 2016, American Society for Microbiology. All Rights Reserved

Emergence of a pandrug-resistant VIM-1-producing Providencia stuartii clonal strain causing an outbreak in a Greek intensive care unit

Abstract Here we describe an outbreak caused by a pandrug-resistant Providencia stuartii strain involving 15 critically ill patients in a Greek intensive care unit (ICU) during September-November 2011. All isolates harboured the blaVIM-1 gene and a class 1 integron structure of 1913 bp as well as blaSHV-5 and blaTEM-1. Pulsed-field gel electrophoresis (PFGE) demonstrated that isolates from all 15 patients belonged to a single P. stuartii clonal type. As all of the infected patients were hospitalised during overlapping time periods, horizontal intra-ICU transmission was considered as the main route for the dissemination of the outbreak strain. The outbreak ended following reinforcement of infection control measures, including implementation of additional barrier precautions for infected patients. © 2015 Elsevier B.V. and the International Society of Chemotherapy.All rights reserved

Daptomycin as adjunctive treatment for experimental infection by Acinetobacter baumannii with resistance to colistin

The emergence of Acinetobacter baumannii with resistance to colistin (ABRC) led to the investigation of daptomycin as an adjunctive to colistin for these isolates. In this study, one ABRC carbapenemase-producing bloodstream isolate was examined. Minimum inhibitory concentrations (MICs) were >512, >512 and 8 µg/mL for imipenem, daptomycin and colistin, respectively. First, a ‘humanised’ model of the pharmacokinetics of daptomycin and colistin was developed in 18 male C57BL/6 mice. Then, 112 mice were infected by intraperitoneal injection of the ABRC isolate and were randomly assigned into four groups of once-daily treatment for 7 days: group A, controls treated with saline; group B, treated with 20 mg/kg colistin; group C, treated with 50 mg/kg daptomycin; and group D, treated with both agents. Survival was recorded for 7 days in ten mice per group. The remaining mice were sacrificed at regular time intervals following bacterial challenge and the bacterial outgrowth in the liver, lung and right kidney was determined. Mean serum concentrations of daptomycin at 15, 30 and 60 min post-dose were 121.8, 110.3 and 100.4 µg/mL, respectively. The respective concentrations of colistin were 13.9, 9.1 and 7.5 µg/mL. The 7-day mortality in groups A, B, C and D was 100%, 50%, 100% and 0%, respectively. Tissue outgrowth of the right kidney was significantly decreased in group D compared with group B after 72 h. Daptomycin used in combination with colistin leads to prolonged survival in an experimental infection by ABRC. Failure of colistin alone is probably related to rebound of tissue outgrowth. © 2019 Elsevier Lt