Survival of Esherichia coli 0157:H7, Staphylococcus aureus, Shigella flexneri and Salmonella spp. in Borde and Shamita: Traditional Ethiopian Fermented Beverages

Abstract

The survival or inhibition of foodborne pathogens in different fermented products are well documented. This prompted the study to evaluate survival of Esherichia coli O157:H7, Staphylococcus aureus, Shigella flexneri and Salmonella spp. in two Ethiopian traditional fermented low-alcohol beverages, Shamita and Borde. The pH of ready-to-consume Shamita and Borde was 4.0 and 3.8, respectively. Samples were separately inoculated with 103 cfu/ml of the test strains for Borde and 106 cfu/ml for Shamita and these were maintained at 32oC. In Shamita, Staphylococcus aureus, Shigella flexneri, and Salmonella survived until 24 h, but were not detectable at 48 h. Esherichia coli O157:H7 could survive until 48 h but was undetectable at 72 h. In Borde, Staphylococcus aureus, and Shigella flexneri survived only until 16 h, whereas Salmonella was eliminated within 12 hours. Esherichia coli O157:H7 survived longer in Borde and was eliminated only at 24 h. The presence of the test strains in the fermented products resulted in decrease of pH by an average of 0.35 units within 48 hours in Shamita and 0.16 units within 24 hours in Borde. The fermented products are low-alcohol beverages and are consumed in large amounts as meal replacements. As they are supposed to be consumed within a few hours after production and pathogens can survive in the product for over 10 hours, contamination of the products with pathogens should be avoided.

Keywords: E. coli O157:H7; Salmonella; Shigella flexneri; Staphylococcus aureus; Traditional fermented beverages.

Ethiopian Journal of Biological Sciences Vol. 6 (1) 2007: pp. 1-10