A Study To Assess the Numbers and Prevalence of Bacillus cereus and Its Toxins in Pasteurized Fluid Milk.

Bacillus cereus is a pathogenic adulterant of raw milk and can persist as spores and grow in pasteurized milk. The objective of this study was to determine the prevalence of B. cereus and its enterotoxins in pasteurized milk at its best-before date when stored at 4, 7, and 10°C. More than 5.5% of moderately temperature-abused products (stored at 7°C) were found to contain >105 CFU/mL B. cereus , and about 4% of them contained enterotoxins at a level that may result in foodborne illness; in addition, more than 31% of the products contained >105 CFU/mL B. cereus and associated enterotoxins when stored at 10°C. Results from a growth kinetic study demonstrated that enterotoxin production by B. cereus in pasteurized milk can occur in as short as 7 to 8 days of storage at 7°C. The higher B. cereus counts were associated with products containing higher butterfat content or with those produced using the conventional high-temperature, short-time pasteurization process. Traditional indicators, aerobic colony counts and psychrotrophic counts, were found to have no correlation with level of B. cereus in milk. The characterization of 17 representative B. cereus isolates from pasteurized milk revealed five toxigenic gene patterns, with all the strains carrying genes encoding for diarrheal toxins but not for an emetic toxin, and with one strain containing all four diarrheal enterotoxin genes (nheA, entFM, hblC, and cytK). The results of this study demonstrate the risks associated even with moderately temperature-abused pasteurized milk and the necessity of a controlled cold chain throughout the shelf life of fluid milk to enhance product safety and minimize foodborne illness.

Microbial survey of selected Ontario-grown fresh fruits and vegetables.

Recent produce-related outbreaks have been receiving heightened media coverage, which has increased public concern toward the safety of fresh fruits and vegetables. In response, the microbial contamination of Ontario-grown fresh fruits and vegetables was evaluated by the Ontario Ministry of Agriculture, Food and Rural Affairs during the summer of 2004. Prior to this survey, information specific to the microbial contamination of Ontario-produced fruits and vegetables was limited. This nonregulatory survey had two objectives: (i) to obtain a general microbiological profile of selected fruits and vegetables produced in Ontario and (ii) to use the information and knowledge gained from this survey to direct and support future on-farm food safety research and food safety programs to manage potential risks. In all, 1,183 samples, including muskmelon (151), scallions and green onions (173), leaf lettuce (263), organic leaf lettuce (112), head lettuce (155), parsley (127), cilantro (61), and fresh market tomatoes (141), were collected and analyzed. Samples were analyzed for Salmonella, Shigella, and generic E. coli. Enrichment cultures positive for E. coli were further assessed for verotoxigenicity. One sample each of Roma tomato and organic leaf lettuce were positive for Salmonella, with no samples yielding Shigella or verotoxigenic E. coli. The E. coli prevalence was highest in parsley (13.4%), followed by organic leaf lettuce (11.6%), leaf lettuce (6.5%), scallions (6.4%), cilantro (4.9%), muskmelon (1.3%), head lettuce (0%), and fresh market tomatoes (0%). These findings, in combination with foodborne illness data, will help target those commodities that require more focused risk mitigation efforts.

Potential sources of microbial contamination in unpasteurized apple cider.

A study was conducted to identify possible sources of microbial contamination and to assess the effect of good cleaning and sanitation practices on the microbial quality and safety of unpasteurized apple cider. Raw unwashed apples, washed apples, cleaning water, fresh cider, and finished cider samples were collected from five Ontario producers over 4 months and microbiologically tested. Total coliforms were found in 31, 71 and 38% of the unwashed apple, water, and washed apple samples, respectively. Escherichia coli was found in 40% of the water samples from one producer alone. The washing step was identified as a potential source of contamination, possibly due to water in the dump tanks seldom being refreshed, and because scrubbers, spray nozzles, and conveyors were not properly cleaned and sanitized. Higher total coliform counts (P < 0.0001) and prevalence (P < 0.0001) in fresh cider compared with those in unwashed apples and washed apples indicated considerable microbial buildup along the process, possibly explained by the lack of appropriate equipment sanitation procedures. Results showed that producers who had better sanitary practices in place had lower (P < 0.001) total coliform prevalence than the rest of the producers. Overall results show that good sanitation procedures are associated with improved microbial quality of fresh cider in terms of total coliforms and that operators who pasteurize and/or UV treat their product should still be required to have a sound good manufacturing practices program in place to prevent recontamination. Cryptosporidium parvum, an important pathogen for this industry, was found in different sample types, including washed apples, water, and fresh and finished cider.