Survival of bioluminescent Escherichia coli O157:H7 in a model system representing fermented sausage production

Abstract

The combined effect of starter culture (107 CFU 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 (100 to 105 CFU/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-clay 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 (100 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').