Exploring Antibiotic Resistance Gene Expression in Acinetobacter baumannii Using Microarray Technology

Background: Antibiotic resistance is a significant challenge in healthcare, particularly in nosocomial infections caused by Acinetobacter baumannii. Efflux pumps play a crucial role in mediating antibiotic resistance in A. baumannii, yet comprehensive evaluation of these pumps and acquired resistance determinants is lacking. Here, we present the development and validation of an oligonucleotide-based DNA microarray for assessing gene expression of efflux pumps and detecting acquired antibiotic resistance determinants in A. baumannii. Objective: The primary objective of this study was to develop a robust microarray platform capable of simultaneously assessing the expression of efflux pump genes and detecting acquired resistance determinants in A. baumannii. Additionally, we aimed to validate the microarray's performance using mutants overexpressing or deficient in efflux pumps and single-step mutants obtained on various antibiotics. Methods: The DNA microarray consisted of probes targeting 78 genes, including 17 efflux systems, 15 resistance determinants, and 19 housekeeping genes. Comparative analysis of mutants, along with quantitative reverse transcriptase PCR validation, was conducted to confirm the microarray's accuracy in detecting efflux pump overexpression. Results: Validation experiments revealed overexpression of RND efflux pumps AdeABC and AdeIJK in mutants obtained on gentamicin, cefotaxime, or tetracycline, as well as identification of a novel efflux pump, AdeFGH, overexpressed in a mutant exposed to chloramphenicol. Clinical isolates showed overexpression of AdeABC and chromosomally encoded cephalosporinase, along with several acquired resistance genes, accounting for the multidrug-resistant phenotype. Conclusion: The developed microarray demonstrates high sensitivity and specificity in detecting efflux pump expression and acquired resistance determinants in A. baumannii. Its potential utility in identifying antibiotic resistance and novel efflux systems highlights its importance in clinical settings.