Influence of raw meat natural background flora on growth of Escherichia coli 0157: H7 in ground beef

RESUMO

Escherichia coli 0157 : H7 foodborne pathogen of increasing importance. It has been involved in several threatening outbreaks, most of them associated with meat products. In this study, the influence of some bacteria from the natural background flora of raw meat over E.coli 0157 : H7 in ground beef stored under refrigeration and at room temperature was evaluated. Different levels of E.coli 0157 : H7 (10 1 - 10 2, 10 3 - 10 4, and 10 6 - 10 7 CFU/g), inoculated in ground beef samples, were challenged with strains of non-pathogenic E.coli, Psudomonas putida or Leuconostoc sp. Growth of the pathogen was monitored using standard cultural methods and an Elisa-type rapid method. Non-pathogenic E.coli, Pseudomonas putida and Leuconostoc sp. did not affect growth of E.coli 0157 : H7 in ground beef, both under refrigeration and at room temperature. Based on these findings, the low occurrence of E.coli 0157 : H7 in raw meat may not be attributed to antagonistic effects of bacteria from the natural background flora.