Sensitivity of Escherichia coli O157 Detection in Bovine Feces Assessed by Broth Enrichment followed by Immunomagnetic Separation and Direct Plating Methodologies

摘要: In order to more precisely predict food safety risks, the fecal presence of food-borne pathogens among animals at slaughter must be correctly determined. Quantification Escherichia coli O157 is also desirable. two separate experiments, detection and enumeration a nalidixic acid-resistant strain E. in bovine feces was assessed by culture on MacConkey agar supplemented with acid (MACnal) compared overnight broth enrichment followed immunomagnetic separation (IMS) direct plating dilutions onto sorbitol containing cefixime tellurite (SMACct). The sensitivity both IMS highly dependent upon initial concentration target organism sample. Sensitivity poor below 100 CFU/g but better, not affected numbers, above this concentration. low concentrations very for IMS. Direct SMACct can used determine magnitude excretion cattle excreting greater than CFU/g. Among positive samples identified SMACct, counts O157:H7 were correlated estimates obtained MACnal plates (r = 0.88, P < 0.001). Because majority excrete less 102 CFU O157/g feces, most studies, including those using methods, probably grossly underestimate prevalence cattle.