Survival of Bioluminescent Escherichia coli O157:H7 in a Model System Representing Fermented Sausage Production

The combined effect of starter culture (107 CPU of lactic acid bacteria per ml), dextrose (0.8%), sodium chloride (2%), nitrite (200 ppm), and temperature (37 and 22°C) on survival of bioluminescent Escherichia coli O157:H7 (l00 to 105 CPU/ml) in brain heart infusion (BHI) broth was determined. Two model systems representing fermented sausage production were evaluated. The first was the “American style” employing high-temperature (37°C) and short-time (1-day) fermentation. The second was the “European style” in which 22°C was used for 3 days. After fermentation, the samples were stored at 10°C and the survival of E. coli O157:H7 was monitored over an extended period of time. In the “American style” model, E. coli O157:H7 survived a more than 34-day period in BHI containing starter culture and dextrose, while it survived for a more than 51-day period in BHI containing starter culture, dextrose, sodium chloride, and nitrite. In the “European style” model, the survival time of E. coli O157:H7 during fermentation was longer in BHI containing starter culture and dextrose than in BHI containing starter culture, dextrose, sodium chloride, and nitrite. E. coli O157:H7 did not survive past 9 days in BHI containing starter culture and dextrose. Similarly, in BHI containing starter culture, dextrose, sodium chloride, and nitrite the lower E. coli O157:H7 inoculations (l00 to 104 CFU/ml) did not survive past 9 days; however, at higher inoculum levels (≥105 CFU/ml) the organism survived more than 30 days. In conclusion, the lower temperature and longer fermentation time (“European style”) is better for elimination of E. coli O157:H7 from a model system representing a fermented sausage production than fermentation at high temperature and short time (“American style”).