Detection of plasmid mediated colistin resistance, mcr-1and mcr-2 genes, in Salmonella spp. isolated from food at retail in Belgium from 2012-2015

A collection of 105 colistin resistant Salmonella isolates collected from 2012-2015 in the national surveillance programme in Belgium, were screened by PCR for the presence of the genes mcr-1 and mcr-2. Of these 1.90% (2/105) and 0.95% (1/105) tested positive for mcr-1 and mcr-2, respectively. The presence of the mcr-1 or mcr-2 determinant has been confirmed by whole genome sequencing (WGS) and allowed the localisation of these 2 genes on IncX4 type plasmids. We report here the presence of mcr-1 and the first mcr-2 gene in Salmonella ever isolated in the Belgian food chain. Although present at retail since 2012, the occurrence is low and sporadic.