Investigation of mcr-1 Gene (Colistin Resistance Gene) Existence in Escherichia coli Isolates Separated from Ross and Aryan Broiler Chicks

Escherichia coli (E. coli) is a Gram - negative rod - shaped bacillus, which is a major pathogen with breeding damage in poultry and causes significant economic losses in the industry of Iranevery year. Antibiotic resistance in this organism is discussed as a major challenge worldwide. Therefore, the aim of this study was to investigate the presence of mcr-1 gene (Colistin resistance gene) in Escherichia coli isolates collectedfrom day - old broilers of Ras and Arian breeds.

This cross - sectional descriptive study was conducted in a period of 4 months,and 120 non - repeated isolates of E. coli were collected from the samples of day - old broiler chickens of the Ras and Arin breeds. Samples were sent to the Kowsar laboratory.  E.coli strains were identified by using the Standard biochemical and microbiology routinetests = Antibiotic sensitivity test was performed according to CLSI instructions on Mueller Hinton agar medium by disk diffusion method and determination of minimum inhibitory concentration (MIC) of Colistin Broth Disk Elution was performed according to CLSI instructions for colistin antibiotic. The presence of colistin resistance genes were investigated by PCR.

Total of 120 E. coli isolates were collected from day - old chicks. Our results could not confirm the presence of mcr-1 positive E. coli among the studied isolates.

It is concluded that despite the important role of food - producing animals in the transmission of antibiotic resistance, they were not the main source of mcr-1 transmission in Iran. This study showed that other mcr species (mcr-2 to mcr-9) may be responsible for the development of colistin resistance in animal isolates in Iran. The possible connection between the pig breeding industry and the high level of mcr carriage in some countries should be clarified in future prospective studies.