Three Escherichia coli Ol57:H7 (EHEC) strains were inoculated separately into portions of commercially prepared mayonnaise held at 25 or 7°C, then examined periodically for survival of detectable EHEC. Four mayonnaise-based sauces including: a) mayonnaise-mustard sauce, b) blue cheese dressing, c) thousand island dressing and d) seafood sauce, were each inoculated with one EHEC strain. Samples of these sauces were held at 5°C, and assayed periodically for survival of detectable EHEC. Both direct plate count and selective enrichment recovery were employed as assay procedures. Escherichia coli O157:H7 strains, when inoculated and mixed into mayonnaise and stored at 25°C, became undetectable after 72 h storage when assayed by direct plating or by selective enrichment. The same strains inoculated into mayonnaise and stored at 7°C were detectable up to 35 days when assayed by direct plating or by selective enrichment. Escherichia coli O157:H7 inoculated into mayonnaise-based sauces and held at 5°C were detectable past 35 days in three of the four sauces. Loss of EHEC culturability occurred within 3 days in mayonnaise-mustard sauce.

The current U.S. Food and Drug Administration (FDA) methodology for detection of Campylobacter, a leading source for foodborne illness, is outdated. The purpose of this study, therefore, was to improve and update the cultural and identification methods found in the FDA/Bacteriological Analytical Manual (BAM). Raw silo milk samples containing typical and atypical strains of Campylobacter jejuni and Campylobacter coli at different levels (5 CFU/25 g, 50 CFU/25 g, and 125 CFU/25 g) were analyzed. Valid results were obtained from 240 test portions. Six inoculated (at the levels described above) and two uninoculated samples were sent to a participating laboratory to mimic a "real-world" scenario. These combined data indicated that the use of sheep blood in combination with enrichment is not necessary. R & F Campylobacter jejuni/Campylobacter coli Chromogenic Plating Medium is significantly (P < 0.05) more sensitive for detection of C. jejuni or C. coli at low inoculation levels than the modified Cefoperazone Charcoal Deoxycholate Agar used in the BAM. The quantitative PCR method described demonstrated rapid confirmation and identification of C. jejuni or C. coli. It reduced the time to isolate C. jejuni or C. coli, and increased the sensitivity compared to the current BAM protocol.

Selected enrichment broths supplemented with the enzyme Oxyrase a membrane‐bound enzyme derived from E. coli were evaluated for recoveries of Campylobacter under normal atmospheric conditions from shellfish. Results indicate that Oxyrase is useful for the recovery of Campylobacter from shellfish. Effect of Oxyrase on growth of Campylobacter were dependent upon physical parameters such as media volume and surface volume area. For example, in the comparision of growth of Campylobacter sp (low to high levels, 1 × 101 to 6/mL) in various media volumes in Stomacher 400 closure bags and 250 mL and 500 mL screw‐capped Erlenmeyer flasks, no campylobacters were recovered using the closure bags. However, all levels of Campylobacter were recovered in the Erlenmeyer flasks. Oxyrase was useful for the recovery of C. jejuni from Pacific oysters (Crossostrea gigas). In one study, Pacific shellstock oysters were allowed to take up 1 × 106 cells of C. jejuni per mL for a period of 5 to 7 h in an artificial seawater aquarium system. Oysters were removed and stored at 4C for 24 days. Uptake in oysters ranged from 0.4 to 114 cells/g. At intervals, oysters were removed and analyzed for C. jejuni by using the Oxyrase method and the FDA/Bacteriological Analytical Manual standard method. Comparison of these methods showed that the Oxyrase method was as reliable as the official FDA method. Oxyrase was also useful for recovering naturally occurring Campylobacter in market oyster shellstock. To measure reproducibility of the method, an in‐house preliminary collaborative study was conducted in the University of Central Venezuela (Caracas). Participants consisted of 6 groups of three microbiologist each from various countries in Central and South America. All groups were successful in recovering Campylobacter jejuni and Campylobacter coli using Oxyrase. Our results indicate that Oxyrase provides microaerobic conditions for growth of Campylobacter from shellfish.

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