Phenotypic and molecular characterization of Acinetobacter baumannii isolates causing lower respiratory infections among ICU patients.

Multi-drug resistant Acinetobacter baumannii has emerged as important nosocomial pathogen associated with various infections including lower respiratory tract. Limited therapeutic options contribute to increased morbidity and mortality. Acinetobacter baumannii has the ability to persist in the environment for prolonged periods. Breach in infection control practices increases the chances of cross transmission between patients and inter/intraspecies transmission of resistance elements. The present prospective work was conducted among patients with lower respiratory tract infections (LRTI) in the intensive care unit (ICU) to study the etiology with special reference to Acinetobacter baumannii and the role of immediate patient environment in the ICU as possible source of infection. Acinetobacter baumannii were characterized for antimicrobial susceptibility, mechanism of carbapenem resistance and virulence determinants. Molecular typing of the clinical and environmental isolates was undertaken to study the probable modes of transmission. Appropriate respiratory samples from 107 patients with LRTI admitted to ICU during September 2016 to March 2017 were studied for likely bacterial pathogens. Environmental samples (n = 71) were also screened. All the samples were processed using conventional microbiological methods. Consecutive Acinetobacter spp. isolated from clinical and environmental (health care workers and environment from ICU) samples were included in the study. Antimicrobial susceptibility was performed as per CLSI guidelines. Carbapenem resistance, mediated by carbapenemase genes (blaOXA-23-like,blaOXA-24-like,blaOXA-58-like and blaNDM-1) were studied by PCR. Biofilm forming ability was tested phenotypically using microtitre plate method. Pulse Field Gel Electrophoresis (PFGE) was used to study clonality of the clinical and environmental isolates. The prevalence of Acinetobacter baumannii was 26.2% (28/107) and 11.26% (8/71) among patients with LRTI and environmental samples respectively. The carbapenem resistance was high, 96.42% (27/28) and 87.5% (7/8) in clinical and environmental isolates respectively. The most common carbapenemase associated with resistance was blaOXA-23-like gene followed by blaNDM-1 among both the clinical and environmental isolates. All isolates were sensitive to colistin (MIC ≤ 1 μg/ml). Biofilm production was observed among all clinical (n = 28) and 87.5% (7/8) of the environmental isolates. Line listing of the cases suggests the occurrence of infections throughout the study period with no significant clustering. On PFGE, 12 clusters were observed and 16/36 isolates were present in one single cluster that included both clinical and environmental isolates which were either carbapenem resistant or sensitive. Carbapenem resistant Acinetobacter baumannii (CRAB) is an important cause of LRTI in the ICU. PFGE suggests spread of carbapenem resistant isolates via cross transmission among patients and the environment. The detection of blaNDM-1 gene among Acinetobacter baumannii and existence of carbapenem resistant and sensitive isolates within the same clones suggests horizontal transmission of resistant genes among various bacterial species. The ability of Acinetobacter baumannii to form biofilms may contribute to its persistence in the environment. This along with breach in infection control practices are the likely factors contributing to this transmission. This information can be used to strengthen and monitor infection control (IC) and the hospital cleaning and disinfection practices to prevent spread of resistant organisms within the ICU. Colistin remains drug of choice for management of CRAB.

Jain M ，Sharma A ，Sen MK ，Rani V ，Gaind R ，Suri JC ... -  《-》

Adaptations of carbapenem resistant Acinetobacter baumannii (CRAB) in the hospital environment causing sustained outbreak.

Sharma S ，Das A ，Banerjee T ，Barman H ，Yadav G ，Kumar A ... -  《-》

A prospective multicenter study on the evaluation of antimicrobial resistance and molecular epidemiology of multidrug-resistant Acinetobacter baumannii infections in intensive care units with clinical and environmental features.

Boral B ，Unaldi Ö ，Ergin A ，Durmaz R ，Eser ÖK ，Acinetobacter Study Group ... -  《Annals of Clinical Microbiology and Antimicrobials》

Emergence and characterization of nosocomial multidrug-resistant and extensively drug-resistant Acinetobacter baumannii isolates in Tehran, Iran.

Acinetobacter baumannii is one of the antibiotic-resistant superbugs that threatens hospitalized patients. Emergence and spread of the multidrug-resistant (MDR) and extensively drug-resistant (XDR) clones cause erratic outbreaks following environmental contamination of hospital settings. The present study intended to characterize the antimicrobial resistant profiles and the genotypes of clinical and environmental isolates of A. baumannii as a result of dissemination of resistant strains. Clinical and environmental isolates of A. baumannii were obtained from patients, staff, and environment of an educational hospital in Tehran. Antimicrobial susceptibility testing was carried out using the disk diffusion and E-test methods. Multiplex PCR was performed for detection of OXA-type genes (blaOXA-23-like, blaOXA-24-like, blaOXA-58-like, and blaOXA-51-like). Genotypic relatedness of the isolates was achieved using repetitive extragenic palindromic element PCR (Rep-PCR) technique. All the isolates were found to be susceptible to colistin and most of them (77%) were non-susceptible to tigecycline. A majority of the clinical and environmental isolates (97%) were considered as MDR strains and 41% as XDR. In multiplex detection, blaOXA-23-like was found in 54% of the isolates, which was the most frequent OXA-type gene. In addition, the frequency of the carbapenem-resistant A. baumannii (CRAB) was observed to be high (96%). In addition, molecular typing showed different Rep patterns of clinical isolates and clonal spread of environmental isolates. The present study highlights the circulation of drug-resistant A. baumannii strains in different wards of hospitals principally in intensive care unit (ICU) as a nosocomial pathogen due to unwise managements.

Salehi B ，Goudarzi H ，Nikmanesh B ，Houri H ，Alavi-Moghaddam M ，Ghalavand Z ... -  《-》

Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii in the Intensive Care Unit of Uruguay's University Hospital Identifies the First rmtC Gene in the Species.

Bado I ，Papa-Ezdra R ，Delgado-Blas JF ，Gaudio M ，Gutiérrez C ，Cordeiro NF ，García-Fulgueiras V ，Araújo Pirez L ，Seija V ，Medina JC ，Rieppi G ，Gonzalez-Zorn B ，Vignoli R ... -  《-》