Evaluation of Plasmid Mediated Colistin Resistance in Colistin Resistant Gram-negative Bacilli

Background: Infections caused by carbapenem-resistant gram-negative bacteria are treated with colonistin as a last resort. However, the increased resistance in recent years is significant for treating multiple drug-resistant infections. Objectives: This study aimed to determine the resistance genes mobile colistin resistance (mcr)-1 and mcr-2 in the colistin-resistant isolates, understand the resistance mechanism, and help with treatment. Methods: Isolates were identified in the Vitek MS automated system. The antibiotic susceptibility was tested with the Vitek 2 Compact automated system. Enteric gram-negative bacilli isolates were stored at -20°C until the molecular study. DNA extraction of colistin-resistant isolates was performed by boiling method. Then, polymerase chain reaction (PCR) optimization was performed using the specific primers, and mcr-1 and mcr-2 genes were investigated by the multiplex PCR method. Results: About 170 enteric gram-negative bacilli isolate were mainly sent from internal medicine (44.7%) and neurology (13.5%) services. According to the species identification, 37.6% of the isolates were Klebsiella pneumonia, and 31.7% were Serratia marcescens. Based on PCR results, mcr-1 and mcr-2 genes were not detected in the isolates. Conclusions: Increased colistin resistance and the worrying discovery of mcr genes require urgent precautions, even though the study did not detect mcr-1 and mcr-2. New studies investigating mcr genes in new isolates are needed to understand the mechanism of resistance and identify resistant isolates.