Aim: The aim of this study was to investigate the prevalence and the mechanisms of carbapenem and colistin resistance in Acinetobacter baumannii clinical isolates in an Algerian hospital.
Results: Twelve isolates were collected between October 2013 and March 2014. All isolates were resistant to almost all antibiotics tested with a high-level resistance to imipenem (minimum inhibitory concentrations [MICs] >32 mg/L) with one strain showing resistance to colistin (MIC=16 mg/L). The results of the modified Hodge test and the modified Carba NP test were positive for all isolates. Besides, the activity of β-lactamases was inhibited by EDTA in only two isolates. All the 12 isolates contained the naturally occurring blaOXA-51-like gene. Ten of them harbored the OXA β-lactamases: blaOXA-23 (six isolates) and blaOXA-24 (four isolates) genes, while two isolates were positive for blaNDM-1 gene. The colistin-resistant isolate producing OXA-24 enzyme harbored a single mutation in the pmrB gene. Multilocus sequence typing demonstrated that the 12 isolates belonged to 2 clones: 10 to ST2 and 2 to ST85.
Conclusions: Here, we describe the mechanisms of carbapenem resistance and we report the first colistin and carbapenemase-producing A. baumannii clinical isolate from a patient in Algeria.