Resistance to Colistin and Detection of mcr-1 Gene in Multidrug-Resistant Pseudomonas Aeruginosa Isolated from Wounds of the Hospitalized Burned Patients

Background: The surge in antibiotic resistance, especially to colistin in multidrug-resistant Pseudomonas aeruginosa (MDR P. aeruginosa) is one of the important factors of mortality in wound infections in burn patients. The aim of this study was to investigate the prevalence of resistance to colistin as a last line treatment in MDR P. aeruginosa isolates from the wounds of hospitalized patients and for the detection mcr-1 gene. Methods: Seventy-two P. aeruginosa isolates were obtained from Imam Musa Kazem Hospitals’ laboratories and confirmed using standard microbiological techniques. Antibiotic sensitivity was evaluated by the standard disk diffusion method against 8 antibiotics and minimum inhibitory concentration (MIC) of colistin was determined. The presence of mcr-1 gene was detected using specific primers by Polymerase chain reaction (PCR) test. Findings: Out of 72 isolates, 50 (69.44%) were identified as MDR P. aeruginosa, with the highest resistance to Levofloxacin (98%) and Ciprofloxacin (92%) and the lowest. Resistance was to piperacillin tazobactam (40%). Only 2% of isolates showed complete resistance to all antibiotics. Colistin resistance was detected in 14% and mcr-1 gene in 2% of the isolates. Conclusion: The resistance of P. aeruginosa to colistin (14%) among the isolates from burn infections in Isfahan and the prevalence of mcr-1 gene (2%) in this study, shows the importance of early detection of colistin resistance, following antibiotic resistance genes and avoid recommending this drug unnecessarily to control hospital infections.