Prevalence and Mechanism of Carbapenem-resistant Genes in Acinetobacter baumannii

Abstract

Coccobacilli with a gram-negative Acinetobacter baumannii is a member of the ESKAPE group of free-living organisms, which are widely found in the environment in places like water, food, soil, sewage, animals, and humans. It is an opportunistic pathogen that has been implicated in numerous nosocomial infections across the globe. Carbapenem resistance has formed into a potential threat to humanity because of its rising prevalence among healthcare facilities. The present study was designed to characterize the presence of carbapenem-resistant genes including multidrug-resistant Acinetobacter baumannii strains, isolated from the tertiary care hospital in Pakistan. A biochemical test was 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-EDTACDT. All 48 A. baumannii strains were further amplified by PCR for detection of OXA-51-like, OXA-23-like, and blaNDM genes. The OXA-51-like gene was detected in 46 strains (95.83%), while OXA-23-like was detected in 44 (91.66%) strains of carbapenem-resistant Acinetobacter baumannii. Moreover, New Dehli MBL, blaNDM gene was identified in four (8.33%) MBL positive carbapenem-resistant Acinetobacter baumannii (CRAB) isolates. All 4 positive 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. A high prevalence of OXA-51-like, and OXA-23-like genes was seen among the carbapenem-resistant Acinetobacter baumannii isolates, followed by blaNDM1. The results of the study revealed that MDR Acinetobacter baumannii strains from two important cities in Pakistan (Rawalpindi and Islamabad) had a significant presence of carbapenem-resistant genes. This finding may result in clinical therapeutic failures.