Investigation of Phenotypic and mcr-1–Mediated Colistin Resistance in Escherichia coli

Özet

This study aimed to investigate colistin resistance in Escherichiacoli isolated from a total of 166 stool samples that were obtainedfrom chickens shipped to slaughter in Turkey and the presenceof the mcr-1 gene, which has been recently discoveredand is one of many genes causing plasmid-mediated colistin resistance.To this end, 200 E. coli isolates were collected and identifiedfrom feces obtained from intestinal samples of the broilerchickens included in this study. To reveal the phenotypic colistinresistance profile, the minimum inhibitory concentration ofcolistin for each isolate was determined using the cation-adjustedbroth microdilution method. Phenotypic colistin resistancewas observed in 15 (7.5%) out of 200 E. coli samples obtainedfrom 7 different poultry slaughterhouses. The presence of themcr-1 gene, which provides plasmid-mediated colistin resistance,was investigated by the polymerase chain reaction methodto detect genotypic colistin resistance. The mcr-1 gene was notdetected in any of the studied samples, including isolates thatexhibited phenotypic colistin resistance. The absence of theplasmid-mediated mcr-1 gene, although colistin resistance wasdetected, suggested that the resistance was of chromosomeorigin or that there were other genes responsible for resistance.However, it is thought that it is necessary to conduct newstudies that will investigate the newly emerging plasmid-mediatedgenes in the future.