Plasmid profile and antimicrobial resistance pattern of extensively-drug resistant clinical bacterial isolates in Erbil City, Iraq

Background: The global rise of antimicrobial resistance (AMR), particularly among extensively drug-resistant (XDR) bacteria, poses a significant challenge to clinical treatment. Plasmid-encoded resistance has an important role in the spread of antibiotic resistance genes across species. This study aimed to characterize the antimicrobial resistance profiles and plasmid content of XDR clinical bacterial isolates collected from healthcare centers in Erbil, Iraq. Method: Out of 140 multidrug-resistant (MDR) isolates screened over four months, 50 XDR isolates were selected for further analysis. Antimicrobial susceptibility testing (AST) was performed using the VITEK 2 Compact system and interpreted according to CLSI 2023 guidelines. Plasmid DNA was extracted and analyzed via 1% agarose gel electrophoresis to determine plasmid number and size. Results: Plasmid carriage was detected in 100% of E. coli and K. pneumonia, followed by A. baumannii (83.3%) and P. aeruginosa (54.5%). Most isolates harbored one to three plasmids, ranging from ~500 bp to >50 kb. Spearman correlation revealed a weak, non-significant relationship between plasmid size and resistance level (P=0.361). Conclusion: Acinetobacter baumannii was the most prevalent XDR species and exhibited resistance to all tested classes of antibiotics. In contrast, Pseudomonas aeruginosa demonstrated a comparatively lower frequency of plasmid carriage. Although plasmid carriage was common, plasmid size alone did not predict resistance severity. These findings underscore the need for molecular characterization of plasmids to better understand resistance dissemination and guide infection control strategies.