Investigating the Occurrence of Presumptive Pathogens in Commercial and Farmers Market Meats

This study investigates the occurrence of specific pathogens in retail meat sold by commercial supermarkets compared to locally sourced markets. Ground beef samples were obtained from commercial, Ôbig box\u27 stores and local, farmers markets and examined for the presence of the presumptive pathogens, Escherichia coli O157:H7 and Salmonella. For the detection of E.coli O157:H7, meat samples were homogenized and enriched overnight in Modified EC media with novobiocin. The enriched cultures were selected onto MacConkey agar with sorbitol, cefixime and tellurite. Presumptive positive colonies were subcultured onto Tryptic Soy Agar with Yeast Extract and further analyzed by relevant biochemical assays. For Salmonella detection, meat samples were enriched first in Universal Pre-enrichment Broth, then in Rappaport-Vassiliadis media, and then plated onto selective media. Suspicious Salmonella colonies were further tested by biochemistry. Presumptive colonies of both E.coli and Salmonella were analyzed by microscopy and serological tests. Serology indicated the presence of E.coli O157:H7 in a single sample. It appears that other non-O157 strains of E.coli were present in samples from both sources. Salmonella was detected in ground beef purchased from a retail supermarket. Confirmed colonies indicated no significant antibiotic resistance