Successfully emerging Acinetobacter baumannii clones from two hospitals in Lima, Perú

Background: Acinetobacter baumannii is an opportunistic nosocomial pathogen responsible for 2–10% of all gram-negative nosocomial infections and is classified in the six most important multidrug-resistant microorganisms in hospitals worldwide. Most frequent and lethal (35-52%) infections include ventilator associated pneumonia and bacteremia. Outbreaks of resistant strains are increasingly reported worldwide, being sustained by similar clusters that successfully spread due to acquisition of antimicrobial resistance genes. These genes include class-D β-lactamases such as blaOXA-23, blaOXA-24 and blaOXA-58, among others. Methods & Materials: This study included 80 non-duplicate clinical samples of Acinetobacter spp. collected from inpatients at two tertiary care hospitals in Lima, Perú. Strains were identified as Acinetobacter baumannii by Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS). Antimicrobial susceptibility was assessed with disk diffusion method according to CLSI guidelines. Resistance genes were detected by PCR and DNA sequencing. The clonal relatedness was examined by pulse-field gel electrophoresis (PFGE). Results: Eighty clinical isolates of Acinetobacter spp were identified as A. baumannii by MALDI-TOF MS and were also positive for the blaOXA-51 by PCR. The majority of isolates (71.43%) were classified as extensive drug-resistant A. baumannii (XDRAB). Resistance was elevated for carbapenems (97.5%) and cephalosporins (89.29%). Susceptibility only remained high for colistin (77.38%) and polymyxin B (72.62%). The blaOXA-40 was detected in 83.75% of the strains, blaOXA-23 in 13.75% and blaOXA-58 in 1.25%. Isolates were classified into nine PFGE clusters. Two main clusters, equally present in both hospitals, however, contained 62.5% and 16.25% of all isolates, respectively and were associated with carriage of blaOXA-40. Conclusion: Acinetobacter baumannii strains in this study showed high resistance levels for all antimicrobials. Carbapenem resistance correlate with the presence of blaOXA-40, blaOXA-23 and blaOXA-58. Susceptibility is mainly restricted to polymyxins. Carriage of the blaOXA-40 gene was associated with two major clones that were endemic in both hospitals and belonged to ST2 and ST79, which constitute epidemic high risk clones that are disseminated worldwide. Interestingly, two smaller clusters carrying the blaOXA-23 gene were also reported, the latter belonging to non-epidemic lineages of A. baumannii. Healthcare systems need to develop and improve current surveillance and infection control programs to prevent spread such successful clusters.