Molecular investigation of qnr A-B genes isolated from antibiotic-resistant Escherichia coli causing mastitis in dairy cows

Mastitis is an important disease that can infect livestock throughout their life. Gram-negative EscherichiaColi is the main cause of most of this disease. The aim is to investigate EscherichiaColi isolates containing fluoroquinolone antibiotic resistance genes in mastitis milk using multiplex PCR technique. In this study,150milk samples from cows suffering from mastitis were used. The samples were sent to the microbiology laboratory of Faculty of Veterinary Medicine of Kazeroon University for evaluation. After culturing the suspected EscherichiaColi colonies, according to the CLSI tables, the sensitivity of the isolated strains was evaluated. The results of electrophoresis of PCR products showed that among the 7 strains of Escherichia coli resistant to flumoquine; The qnrS gene was observed in one strain and the qnrB gene was observed in one strain, and one strain had both qnrS and qnrB genes. In this study, among 17 isolates of Escherichia coli resistant to enrofloxacin (36.36%), 1 isolate has qnrB gene, 1 isolate has qnrS gene and 1 isolate has both qnrS and qnrB genes. occurrence of resistance to quinolones in Escherichia coli pathogenic strains can be a danger to public health. The most abundant pattern of multiple resistance obtained was related to the strains that were resistant to several antibiotics at the same time.The results showed that qnr S and qnrB genes are the most important genetic factors involved in resistance against quinolones and fluoroquinolones.