Identification of novel drug targets to counteract efflux pump mediated multidrug resistance in Acinetobacter baumannii

Abstract

The emergence of multidrug-resistant (MDR) Acinetobacter baumannii poses an escalating threat to the healthcare system worldwide. A significant factor contributing to increasing resistance is the overexpression of chromosomally encoded efflux pumps, which expel antibiotics from bacterial cells, thereby rendering treatments less effective. The efflux pumps not only mediate resistance to antibiotics through drug efflux but also work synergistically with other resistance mechanisms, thereby doubling the resistance. Despite their crucial role in antibiotic resistance, understanding of the structure, function, mechanisms of action, and regulation of efflux pumps remains limited, which is necessary for devising effective strategies to restore drug susceptibility and to combat MDR isolates. In this context, the present study evaluated the prevalence of efflux pump overexpression in clinical A. baumannii isolates using phenotypic and genotypic methods and identified potential therapeutic targets employing a network-based approach. A total of 172 A. baumannii isolates were collected and subjected to antibiotic susceptibility tests using the Kirby-Bauer disk diffusion method. All the isolates were found to be MDR, with 94.76 % showing resistance to carbapenems. Efflux pump overexpression was detected in 54.65 % of isolates using the Ethidium-Bromide Agar Cartwheel method, and efflux pump inhibitory activity was observed in 68.71 % of isolates using cyanide m-chlorophenylhydrazone (CCCP). A total of thirteen efflux pump genes were detected in the tested isolates using diagnostic PCR, which were considered for interaction network analysis using STRING. Clustering analysis of the merged network identified two highly interconnected clusters, each comprising functional partners crucial for efflux pump function and regulation. Key hub genes, including AdeB, AdeJ, AdeK, AdeC, macB, tolC, AIL80285.1, AdeR, and AdeS, were identified as primary targets due to their significant influence on the network. Additionally, 24 clustered genes were pinpointed as potential drug targets for developing novel therapeutics to combat the formidable challenge of efflux pump-mediated MDR in A. baumannii.