High prevalence of TEM, VIM, and OXA-2 beta-lactamases and clonal diversity among Acinetobacter baumannii isolates in...

Acinetobacter baumannii is an opportunistic pathogen that causes nosocomial infections with high mortality. Treatment options are limited owing to its resistance to numerous antibiotics. Here, we sought to determine the antibiotic susceptibilities of A. baumannii isolates, investigate clonal relationship among the strains, and determine the frequency of beta-lactamase resistance genes.

The identification and antibiotic susceptibilities of 69 A. baumannii strains were determined using a BD-Phoenix automated system. The presence of blaOXA-2, blaOXA-10, blaOXA-23, blaOXA-24/40, blaOXA-51, blaOXA-58, blaTEM, blaSHV, blaIMP, blaVIM, and blaGIM genes were investigated using polymerase chain reaction (PCR), and clonal relatioships among the isolates were determined using pulsed-field gel electrophoresis (PFGE).

All strains were resistant to ampicillin-sulbactam, gentamicin, cefepime, ciprofloxacin, and ceftriaxone. While 65 of the 69 strains (94.2%) were resistant to piperacillin-tazobactam, amikacin, imipenem, and meropenem, all strains were susceptible to tigecycline and colistin. The frequencies of blaOXA-51, blaOXA-23, blaTEM, blaOXA-2, blaVIM, and blaSHV were 100%, 94.2%, 53.6%, 21.7%, 14.5%, and 2.9%, respectively. Based on PFGE results, 56 of the 69 strains were clonally related, and the clustering rate was 81.2%. No common outbreak isolate was detected.

The most prevalent OXA genes were blaOXA-51, blaOXA-23, and blaOXA-2. Furthermore, blaTEM, blaSHV, and blaVIM, which are common in Enterobacterales and Pseudomonas spp, were detected, suggesting horizontal gene transfer had occurred between bacteria. No single clone outbreak was detected by PFGE. However, multiclonal spread and the high clustering rate suggest cross-contamination. Therefore, in future, more effective infection control measures must be implemented.