Virulence and antimicrobial resistance profiles of Escherichia coli encoding mcr gene from diarrhoeic weaned piglets in Korea during 2007-2016.

OBJECTIVE

This study aimed to analyse the presence of mcr genes and virulence genes in Escherichia coli (E. coli) isolates from diarrhoeic piglets between 2007-2016 in Korea.

METHODS

A total of 364 E. coli isolates were obtained from diarrhoeic weaned piglets between 2007-2016. Minimum inhibitory concentrationss were determined according to the Clinical and Laboratory Standards Institute (CLSI). DNA samples were tested for the presence of mcr-1, mcr-2 and mcr-3 genes. Furthermore, multiplex PCR was used to detect toxin, fimbrial and non-fimbrial adhesin genes.

RESULTS

It was found that 2.5% (nine of 364) of the isolates carried the mcr genes. Four isolates carried the mcr-1 gene and eight isolates had the mcr-3 gene. Three isolates carried both mcr-1 and mcr-3 genes; the mcr-2 gene was not found. All isolates carrying mcr genes were multidrug-resistant. F18 (77.8%, seven of nine) and Stx2e (44.4%, four of nine) were frequently detected in E. coli carrying the mcr gene.

CONCLUSIONS

In conclusion, it would appear that the most prevalent mcr gene of E. coli from diarrhoeic weaned piglets in Korea was mcr-3. It is believed that this is the first report of two plasmid-mediated colistin resistance genes - mcr-1 and mcr-3 - coexisting in the same isolates (0258, 0491, 0516) from piglets with diarrhoea in Korea. Those mcr-positive isolates showed multidrug resistance and the majority of those encoded Stx2e and F18. This indicates the risk of inefficient treatment for oedema disease in weaned piglets.