Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) have been a challenging concern of health-care associated infections. The aim of the current study was to investigate the molecular epidemiology and clonal dissemination of CRAB isolates in a Chinese teaching hospital.
Methods: Non-duplicate clinical A. baumannii isolates were collected from inpatients, and we measured the minimal inhibitory concentrations to determine antimicrobial susceptibility. Polymerase chain reaction (PCR) and sequencing were performed to detect carbapenem-resistance genes and occurrence of transposons among CRAB isolates. Moreover, the genetic diversity among isolates and clonal dissemination were determined by repetitive element PCR-mediated DNA fingerprinting (rep-PCR) and multilocus sequence typing (MLST).
Results: A total of 67 CRAB isolates displayed resistance to most of the antibiotics tested in this study, except tigecycline. We detected blaOXA-23, blaOXA-51, blaOXA-58, and blaVIM genes in 94.0%, 100.0%, 1.5%, and 80.6% of the CRAB isolates, respectively. Nevertheless, 74.6% of the CRAB isolates co-harbored the blaOXA-23 and blaVIM. Only one type of transposons was detected: Tn2008 (79.1%, 53/67). Although 12 distinctive types (A-L) were determined (primarily A type) ST195 was the most prevalent sequence type (ST). ST368, ST210, ST90, ST829, and ST136 were also detected, and all belonged to clonal complex 208 (CC208) and global complex 2 (GC2).
Conclusion: The blaOXA-23 and blaVIM genes contributed to the resistance among CRAB isolates collected in our study. Notably, most of the CRAB strains co-harbored blaOXA-23 and blaVIM genes, as well as Tn2008, which could contribute to clonal dissemination. The prevalence of such organisms may underlie hospital acquired infections.