SURVIVAL OF ESCHERICHIA-COLI O157-H7 IN MAYONNAISE AND MAYONNAISE-BASED SAUCES AT ROOM AND REFRIGERATED TEMPERATURES

Three Escherichia coli O157:H7 (EHEC) strains were inoculated separately into portions of commercially prepared mayonnaise held at 25 or 7-degrees-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-degrees-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-degrees-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-degrees-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-degrees-C were detectable past 35 days in three of the four sauces. Loss of EHEC culturability occurred within 3 days in mayonnaise-mustard sauce.