Conditions affecting autoinducer-2-based quorum sensing of Escherichia coli O157:H7 on fresh beef.

Abstract

This study evaluated whether inoculated (none, 1, 5 log colony-forming units [cfu]/cm(2)) Escherichia coli O157:H7 would result in detection of autoinducer (AI)-2-like activity on beef. Inoculated fresh beef, containing low (LNB) or high (HNB) initial levels of natural flora, was analyzed for bacterial populations and AI-2-like activity during aerobic or vacuum-packaged storage (4, 10, 25C). As expected, no growth of E. coli O157:H7 was detected at 4C, while at 10C, growth was detected only on LNB samples stored aerobically; AI-2-like activity was minimal (P >= 0.05) at both temperatures. E. coli O157:H7 showed more growth in LNB than HNB, and in aerobically than vacuum-packaged samples inoculated with 1 log cfu/cm(2) of the pathogen during storage at 25C. AI-2-like activity was generally higher in LNB than HNB samples stored aerobically at 25C, while no significant AI-2-like activity was detected in samples stored in vacuum packages. The results indicated that E. coli O157:H7 may exhibit AI-2-like activity on aerobically stored beef in the presence of lower initial levels of natural flora, and at temperatures allowing prolific growth of the pathogen. Thus, AI-2-based quorum-sensing of E. coli O157:H7 may not be of importance in beef stored at low temperatures.