Phenotypic and genotypic characterization of multidrug-resistant Acinetobacter baumannii isolated in Algerian hospitals

Introduction: the aim of this study was to investigate the drug-resistance and the molecular characterization of carbapenemases, ESBL, and aminoglycoside-modifying enzymes among Acinetobacter baumannii clinical isolates in Algerian hospitals. Methodology: a total of 92 A. baumannii isolates were collected between 2012 and 2016. Antimicrobial susceptibility testings were performed for beta-lactams, aminoglycosides, fluoroquinolones, trimethoprim-sulfamethoxazole, rifampicin and colistin. The phenotypic characterization of beta-lactamases was investigated. For 30 randomly targeted strains, the carriage of the carbapenemases, ESBL and aminoglycoside-modifying enzymes -encoding genes was determined by PCR. Sequencing was carried out for carbapenemases and ESBL genes. Results: most of the 92 isolates studied were recovered from hospitalized patients (93.5%) and were mainly from intensive care units (51. 1%) and orthopedics (19.6%). The strains were collected primarily from low respiratory tract (33.7%), wounds (23.9%) and urine (16.3%). Multidrug-resistant A. baumannii strains were prevalent (96.7%). High rates of resistance were observed for almost all antibiotics tested (>70%) excluding rifampicin (7.6%) and colistin (5.4%). For the five colistin-resistant strains, MICs ranged between 4 and 128 mu g/mL. Positive MBL (83.7%) and ESBL (23.9%) strains were identified. Regarding beta-lactams, the bla(NDM) and both bla(SHV) and bla(CTX-M1) genes were detected in five and two strains respectively. Sequencing of the genes revealed the presence of blaNDM-1, bla(CT)(X-)(15), and bla(SHV-)(33). For aminoglycosides, aac(6')-Ib, ant(2 '')-I and aph(3')-VI genes were detected in three, seven and six strains respectively. Conclusions: here, we report the first co-occurrence of extended-spectrum beta-lactamases SHV-33 and CTX-M-15, the carbapenemase NDM-1 and the emergence of colistin-resistant A. baumannii in Algerian hospitals.