Fate of Enterohemorrhagic Escherichia coli O157: H7 in Commercial Mayonnaise

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Abstract
The fate of enterohemorrhagic Escherichia coli O157:H7 was determined in three different lots of commercial mayonnaise, including four different samples from a lot implicated in an outbreak of E. coli O157:H7 infection. The initial pH of the products ranged from 3.6 to 3.9. Products were inoculated with 6.5 × 103 E. coli O157:H7/g and incubated at 5 or 20°C. Escherichia coli O157:H7 did not grow at either temperature but survived for 34 to 55 days at 5°C and for 8 to 21 days at 20°C, depending on the lot. Survival was greatest in real mayonnaise purchased at retail among six mayonnaise samples which included a reduced calorie mayonnaise. Escherichia coli O157:H7 populations decreased between 2- and 100-fold by 3 weeks at 5°C, and between 10- and 1,000-fold by 7 days at 20°C. There was little or no change in pH (Lactobacillus count (< 1 log10 CFU/g) for the duration of the study. Commercial mayonnaise manufactured under good manufacturing practices is not a public health concern. Abusive handling of mayonnaise resulting in cross-contamination with E. coli O157:H7-contaminated food or contamination by an infected foodhandler is the principal basis for concern.

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