Survival of bacterial enteric pathogens in traditional fermented foods

The survival of strains of bacterial enteric pathogens was investigated in two traditional fermented foods (mahewu and sour porridge) and in unfermented porridge. The foods were inoculated with cell suspensions of Salmonella, Shigella, Campylobacter, Aeromonas species and pathogenic Escherichia coli which had a final concentration of 10(6)-10(7) cfu/ml of food. None of the strains of Aeromonas and Campylobacter were detected in mahewu and sour porridge 20 min after inoculation. The salmonellas were not found 4 h after inoculation in either fermented foods but the shigellas and pathogenic E. coli strains were more tolerant to the low pH of the fermented foods. Some of the shigellas and pathogenic E. coli strains survived for 24 h after inoculation but showed a sharp decrease in numbers. All the strains of the enteric pathogens survived for 24 h in the unfermented porridge and increased in the numbers except for campylobacters, the numbers of which declined. These results suggest that the traditional fermented foods have bacteriostatic and bactericidal properties and are unlikely to play a major role in the transmission of bacterial enteric pathogens.