Escherichia coli and Salmonella spp. mcr-1 gene carriers at a pig slaughterhouse in Medellín (Colombia)

Objective. This study aimed to evaluate the acquired mcr-1 gene-mediated colistin resistance in Escherichia coli and Salmonella spp. isolates obtained from fecal samples in pigs destined for human consumption at slaughterhouse located in Medellín (Colombia). Materials and methods. A descriptive study was carried out, in which 190 fecal samples were collected from pigs at the slaughterhouse in March 2020. Colistin sulfate-supplemented chromogenic and MacConkey agars (2 mg/l) were used for the screening of colistin-resistant enterobacteria. The selected isolates were analyzed by PCR to identify the presence of the mcr-1 gene. Bacterial identification and antibiotic susceptibility profile were performed on mcr-1 gene-positive isolates by the automated Microscan® system. The information was collected and analyzed using descriptive statistics. Results. The 70.52% (134/190) of the animals were positive for colistin-resistant isolates by the screening test. The 15.78% (30/190) of the isolates were mcr-1 gene carriers, of which 1.05% (2/190) belong to Salmonella enterica species and 4.21% (8/190) were E. coli. A multiple antibiotics resistance profile (10/10) and an extended-spectrum beta-lactamase (ESBL) -producing E. coli were identified in all the isolates carrying the mcr-1 gene. Most of the pigs with enterobacteria carrying the mcr-1 gene came from farms located in the province of Antioquia, and all belonged to the growing-finishing production stage. Conclusions. This study evidences the circulation of the mcr-1 type gene in pigs at the time of slaughter, representing a potentially serious threat to public health due to possible implications in the food chain.