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 mcrgenes require urgent precautions, even though the study did not detect mcr-1 and mcr-2. new studies investigating mcrgenes in new isolates are needed to understand the mechanism of resistance and identify resistant isolates.