Molecular characterization of carbapenem-resistant Acinetobacter baumannii clinical isolates from Egyptian patients

Acinetobacter baumannii ( A . baumannii ) represents a global threat owing to its ability to resist most of the currently available antimicrobial agents. Moreover, emergence of carbapenem resistant A . baumannii (CR-AB) isolates limits the available treatment options. Enzymatic degradation by variety of ß-lactamases, have been identified as the most common mechanism of carbapenem resistance in A . baumannii . The alarming increase in the prevalence of CR-AB necessitates continuous screening and molecular characterization to appreciate the problem. The present study was performed to assess the prevalence and characterize carbapenemases among 206 CR-AB isolated from various clinical specimens collected from different intensive care units at Kasr Al-Aini Hospital. All isolates were confirmed to be A . baumannii by detection of the bla OXA-51-like gene. Molecular screening of 13 common Ambler class bla carbapenemases genes in addition to insertion sequence (IS-1) upstream OXA-23 were performed by using four sets of multiplex PCR, followed by identification using gene sequencing technology. Among the investigated genes, the prevalence of bla OXA-23, and bla OXA-58 were 77.7%, and 1.9%, respectively. The IS Aba1 was detected in 10% of the blaOXA -23 positive isolates. The prevalence of metallo-β-lactamases (MBLs) studied; bla NDM-1, bla SPM, bla VIM, bla SIM-1 were 11.7%, 6.3%, 0.5%, and 0.5% respectively. One of class A; bla KPC was detected in 10.7% of the investigated isolates. bla OXA-24/40, bla IMP, bla GES, bla VEB and bla GIM were not detected in any of the studied isolates. Moreover, 18.4% of the isolates have shown to harbor two or more of the screened bla genes. We concluded that the most prevalent type of ß-lactamases genes among CR-AB isolates collected from Egyptian patients were bla OXA-23 followed by bla NDM-1 and bla KPC.