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

RATIONALE: 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.

OBJECTIVE: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSION: 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.