Pathogenic strains of Escherichia coli isolated from different samples in a rural community in San Luis Potosí, Mexico

Resumen

Escherichia. coli is a bacterium that, in its evolutionary process, has diversified, remaining part of the intestinal microbiota and acting as both an intestinal and extraintestinal pathogen. Transmission of this microorganism occurs through the ingestion of food or water contaminated with human or animal feces. The objective was to understand the transmission cycle of E. coli strains causing diarrhea in a rural community in the state of San Luis Potosí, Mexico. Samples of forage irrigated with wastewater, feces, and milk from cattle fed this forage were analyzed. Seventy-four (74) samples were evaluated: 15 alfalfa, 29 milk, and 30 feces. Bacterial isolation was performed on selective media, and identification was carried out using biochemical tests for Enterobacteriaceae. The E. coli isolates obtained were phenotypically characterized using specific sera (SERUNAM), and their phylogroup was determined by PCR assays. Isolates obtained were 237: E. coli (48.9 %) and Enterobacter sp. (30.2 %) were the most frequently isolated bacteria. Serotyping of E. coli showed the enterotoxigenic pathotype (ETEC) serogroups O6 and O8 in the different samples analyzed. Phylogroups analysis showed the presence of strains B1 and A, defined as commensal, and B2 and D, virulent. The results obtained from the different samples analyzed indicate, among other things, the presence of strains of the ETEC pathotype, a group associated with the pathogenesis of diarrhea. These findings suggest that contaminated irrigation water contributes to the transmission of the various bacteria identified in the pastures consumed by livestock and from the animals' feces to milk and dairy products. This series of events completes the transmission cycle to humans of pathogenic strains from groups associated with the pathogenesis of diarrhea.