Growth and Enrichment Medium for Detection and Isolation of Shiga Toxin-Producing Escherichia coli in Cattle Feces

• Published in: Journal of food protection 2008-05, Vol.71 (5), p.927-933
• Main Authors: Hussein, H.S, Bollinger, L.M, Hall, M.R
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; bacterial contamination; beef cattle; Biological and medical sciences; Cattle; Colony Count, Microbial; Culture Media - chemistry; Dose-Response Relationship, Drug; enrichment culture; Escherichia coli O157:H7; feces; Feces - microbiology; food contamination; Food Contamination - prevention & control; Food industries; Food Microbiology; food pathogens; Fundamental and applied biological sciences. Psychology; General aspects; Humans; Immunoassay; isolation; Methods of analysis, processing and quality control, regulation, standards; microbial detection; on-farm food safety; plate count; Serotyping; shedding; Shiga-like toxins; Shiga-Toxigenic Escherichia coli - drug effects; Shiga-Toxigenic Escherichia coli - growth & development; Shiga-Toxigenic Escherichia coli - isolation & purification; Temperature; Time Factors; Vancomycin - pharmacology
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028x-71.5.927

Detection methods of Shiga toxin-producing Escherichia coli (STEC) in cattle feces varied in using enrichment media containing different antibiotic combinations. To examine efficacy of a new detection method for STEC, three O157:H7 (ATCC 43889, 43890, and 43895) and 41 non-O157:H7 (members of the O1, O15, O26, O86, O103, O111, O125, O127, O128, O136, O146, O153, O158, O165, O166, and O169 serogroups) isolates were tested. These isolates were grown in tryptic soy broth for 6 h, and their concentrations were determined before inoculation of tubes containing 1 g of cattle feces (sterile [experiment 1; evaluating growth] and fresh [experiment 2; evaluating enrichment]) to simulate the high and low levels of STEC shedding by cattle (10⁵ versus 10² CFU/g feces, respectively). Eight STEC isolates (the three O157:H7 and five non-O157:H7 selected at random) were tested at a very low level (10 CFU/g feces). The feces were incubated in 50 ml of brain heart infusion broth containing potassium tellurite, novobiocin, and vancomycin (2.5, 20, and 40 mg/liter, respectively) and cefixime (50 g/liter) at 37°C for 12 h and tested for STEC (VTEC [verotoxin-producing E. coli]-Screen assay [agglutination immunoassay]). Potential STEC isolates were recovered, characterized biochemically, serotyped, and tested for toxin production using Vero (African green monkey kidney) cell toxicity assay and agglutination immunoassay. In both experiments, all the STEC isolates used for fecal inoculation were recovered at the concentrations tested. Our medium supported growth of and enrichment for a wide range of STEC isolates.