Carbapenem-hydrolyzing Oxacillinase Genes in Clinical Isolates of Acinetobacter baumannii

Aims: We aimed in this study to detect the prevalence of carbapenem-hydrolyzing oxacillinase genes among Acinetobacter baumannii clinical isolates recovered from Assiut University Hospitals, Egypt.
Methods: The antimicrobial susceptibilities of 23 non-repetitive Acinetobacter baumannii clinical isolates collected from patients with multiple types of infections were determined. Amplification of blaOXA-23, blaOXA-51, and blaOXA-58 genes was performed by PCR.

Results: Acinetobacter baumannii isolates showed high resistance to carbapenems and other antibiotics. Eleven (48%) isolates were extensively drug resistant and 12 (52%) isolates showed pandrug resistance. Among 23 Acinetobacter baumannii strains; oxacillinase genes were detected in 19 (83%) strains, none of the examined genes were found in 4 (17%) strains. Twelve (52%), 9 (39%), and 4 (17%) isolates harbored blaOXA-51, blaOXA-23, and blaOXA-58 genes, respectively, either in single form (12 isolates; 52%) or combined (7 isolates; 30%). blaOXA-producers associated with longer hospital stay and poor outcome. A. baumannii isolates expressed blaOXA-23 and blaOXA-58 genes, had higher MIC for carbapenems than blaOXA-51 gene.

Conclusion: We concluded that, the presence of oxacillinase genes, especially blaOXA-23 and blaOXA-58, may convey resistance to carbapenems in Acinetobacter baumannii isolates and are associated with high comorbidities and poor outcome in patients.