Evaluation of culture conditions and enumeration methods of enteric bacteria isolated from ground beef

An established protocol for the enrichment of Escherichia coli using E.coli Media with Novobiocin (ECM) was compared to a more convenient universal enrichment media, Universal Pre-enrichment Broth (UPB). Additionally, microbial growth after various incubation times of both media at 24, 36 and 48 hours was compared. There is no significant difference between ECM and UPB for the enrichment of E. coli isolated from raw meat sources. However, ECM appears to be better at enriching and isolating presumptive pathogens, such as E.coli O157:H7. Furthermore, we compared a commercially available Colilert-18 enumeration system to a novel, ready to use, Compact Dryª system. Because Colilert-18 is routinely used for water analysis and Compact Dryª is designed for the enumeration of coliforms from raw materials and environmental surfaces, we were therefore interested to see which of these systems would be most effective using samples collected from raw meat sources. Preliminary results indicate that for highly concentrated meat samples, Compact Dryª media may be more efficient at obtaining coliform and E.coli counts