High prevalence of clonally related multiple resistant Salmonella Infantis carrying class 1 integrons in broiler farms.

The poultry industry in Iran is the main supplier of protein in the food chain. In the present study, we showed the importance of the possible dissemination of clonally related multiple drug resistant (MDR) Salmonella Infantis in broiler farms in Iran. In total, 156 fecal samples belonging to 23 poultry farms in Razavi Khorasan province, northeast of Iran, were examined for the presence of Salmonella serovars. Molecular serotypes and serogroups, class 1 and 2 integron types, colistin resistance genes ( mcr1 and mcr2) and antimicrobial susceptibility patterns were determined on the recovered Salmonella isolates. Based on PCR analysis, 30 recovered Salmonella isolates were identified asS. Infantis (23 isolates; 76.6%),S. Enteritidis (six isolates; 20%), and one isolate (3.3%) was not serotyped by the applied method. Class 1 integrons were detected in 22 isolates (95.6%) and class 2 integrons were not detected in any of the isolates. Although colistin resistance was prevalent in disc diffusion test, mcr-1 and mcr-2 genes were not detected. All class 1 integrons carried the cassette aadA1 gene. All Salmonella isolates were resistant to colistin and amoxicillin/clavulanic acid and MDR patterns were observed in most (96.6%) isolates. This study revealed a high prevalence rate of S. Infantis and the presence of class 1 integrons in broiler farms. The presence of the same integron cassettes in the sequenced isolates suggests that strains are clonally related. Stringent monitoring programs are required to prevent the spreading of MDR Salmonella serovars into food chain via poultry products.

Molecular survey of mcr1 and mcr2 plasmid mediated colistin resistance genes in Escherichia coli isolates of animal origin in Iran.

OBJECTIVES: The emergence of colistin-resistant Enterobacteriaceae from human and animal sources is one of the major public health concerns as colistin is the last-resort antibiotic for treating infections caused by multidrug-resistant Gram-negative bacteria. We aimed to determine the prevalence of the prototype widespread colistin resistance genes (mcr-1 and mcr-2) among commensal and pathogenic Escherichia coli strains isolated from food-producing and companion animals in Iran. RESULTS: A total of 607 E. coli isolates which were previously collected from different animal sources between 2008 and 2016 used to uncover the possible presence of plasmid-mediated colistin resistance genes (mcr-1 and mcr-2) by PCR. Overall, our results could not confirm the presence of any mcr-1 or mcr-2 positive E. coli among the studied isolates. It is concluded that despite the important role of food-producing animals in transferring the antibiotic resistance, they were not the main source for carriage of mcr-1 and mcr-2 in Iran until 2016. This study suggests that the other mcr variants (mcr-3 to mcr-9) might be responsible for conferring colistin resistance in animal isolates in Iran. The possible linkage between pig farming industry and high level of mcr carriage in some countries needs to be clarified in future prospective studies.