Plasmid Profiling and Post-Curing Antibiotic Susceptibility Evaluation of Selected Multidrug-Resistant Surgical Site Infection Bacterial Isolates

Background: Multidrug-resistant (MDR) bacterial pathogens associated with surgical site infections (SSIs) represent a major therapeutic challenge due to widespread dissemination of plasmid-mediated antimicrobial resistance. Characterizing plasmid profiles and determining the contribution of plasmids to antibiotic resistance are essential for understanding resistance mechanisms and improving SSI treatment outcomes. Objective: This study investigated the plasmid profiles of selected MDR bacterial isolates recovered from patients with surgical site infections and evaluated the effect of plasmid curing on antimicrobial susceptibility. Materials and Methods: Multidrug-resistant bacterial isolates obtained from post-operative wound specimens were identified using standard microbiological and biochemical techniques. Antibiotic susceptibility testing was performed before and after plasmid curing. Plasmid DNA was extracted using the alkaline lysis method, profiled by agarose gel electrophoresis, and cured with ethidium bromide. Changes in antibiotic susceptibility following plasmid curing were subsequently evaluated. Results: All selected MDR isolates harboured plasmids, with a common plasmid of approximately 3 kb detected in all isolates, while one Staphylococcus aureus isolate possessed an additional 5 kb plasmid. Complete plasmid curing resulted in the elimination of both single and multiple plasmids and significantly enhanced susceptibility to selected antibiotics (P < 0.05), indicating that resistance was predominantly plasmid mediated. Conclusion: This study findings demonstrate that plasmids play a significant role in mediating multidrug resistance among bacterial pathogens associated with surgical site infections.