Survival of Escherichia coli O157 : H7 and Salmonella on chill-stored vacuum or carbon dioxide packaged primal beef cuts

The ability of two Escherichia coli O157:H7 strains (E27, a cattle isolate, and B6-914 gfp-91, a fluorescent marker strain) and two Salmonella serotyp es (S. typhimurium and S. brandenberg) to survive on chilled preservatively packaged primal beef cuts was examined. Each of the strains was inoculated separately at two dilution levels (10(3) and 10(5) cfu g(-1)) onto 500 g b eef steaks, packaged under vacuum or 100% carbon dioxide, and stored, with uninoculated controls, for 6 weeks at - 1.5 degreesC, then for 2 weeks at 4 degreesC. Bacterial numbers were determined by dilution and incubation at 37 degreesC for 24 h on either Sorbitol McConkey Agar or Xylose Lysine Deso xycholate Agar for E. coli O157:H7 and Salmonella samples, respectively. Co unts were corrected for background growth and their accuracy checked using immunological tests. Fluorescent E. coli O157:H7 B6-914 gfp-91 was also cou nted under ultra-violet light. No significant changes in numbers of the E. coli O157:H7 or Salmonella strains occurred during storage at either - 1.5 or 4 degreesC packaged under either vacuum or carbon dioxide. The ability o f these pathogens to survive standard preservative packaging conditions is different from that reported from their generic counterparts and therefore a cause for public health concern. (C) 2001 Elsevier Science B.V. All right s reserved.