Prevalence and mechanism of carbapenem-resistant genes in Acinetobacter baumannii

Abstract Background Gram-negative Acinetobacter baumannii is an opportunistic pathogen, being highly reported for causing various nosocomial infections worldwide. The present study aimed to characterize the presence of carbapenem-resistant genes among multidrug-resistant Acinetobacter baumannii strains, isolated from the tertiary care hospital in Pakistan. Methods Biochemical tests were performed for the initial identification of bacterial strains and further confirmed by MALDI-TOF mass spectrometry. Antibiotic susceptibility testing was done by using the standard Kirby-Bauer disk diffusion method, and carbapenem resistance determinants were further screened Metallo-beta-lactamase manufacture through Imipenem/Imipenem-EDTA-CDT. All 46 imipenem-resistant and 44 MBL positive isolates of A. baumannii were further amplified by PCR. Results The OXA-51-like gene was detected in 45 strains (97.82%), while OXA-23-like was detected in 44 (95.65%) strains of carbapenem-resistant Acinetobacter baumannii . Moreover, New Dehli MBL, blaNDM gene was identified in four (9.09%) MBL positive carbapenem-resistant Acinetobacter baumannii (CRAB) isolates. All blaNDM isolates were co-expressed by the OXA-23-like gene while OXA-51-like was absent in one blaNDM positive strain of carbapenem-resistant Acinetobacter baumannii isolates. Conclusion A high prevalence of OXA-51-like and OXA-23-like genes was seen among the carbapenem-resistant Acinetobacter baumannii isolates, followed by blaNDM-1. The study findings showed the significant presence of carbapenem-resistant genes in MDR Acinetobacter baumannii strains, which may lead to clinical therapeutic failures.