Prevalence of E. coli, thermotolerant coliforms, Salmonella spp. and Vibrio spp. in ready-to-eat foods : Pemba island, United Republic of Tanzania

This study is aimed to evaluate the microbiological quality of ready-to-eat foods in Pemba island. A total of 300 food samples have been analysed: 66 household preparations, 115 samples of raw cow milk, and 119 fried sea-foods. The thermotolerant coliforms have been detected in 34% sea-foods, 58% household meals, and 98% milk samples; the coliforms count is 5 x 10(2), 10(3), and 3 x 10(4) cfu/g, respectively. E. coli is the species most frequently isolated: 60 on 100 strains agglutinate one of the tested polyvalent antisera. Salmonella spp. have been found exclusively in cow milk (11%); in 15% sea-foods V. alginolyticus has been isolated. The prevalence of faecal contamination is extremely high in cow milk, a critical vehicle for the transmission of pathogens, probably for a lacking thermal treatment (pasteurization). Salmonella spp., V. cholerae, and V. parahaemolyticus have not been isolated from boiled or fried foodstuffs, but in any case the cooked foods are faecally contaminated: their contamination occurs likely after preparation and before consumption. The identification of risk factors for the faecal contamination could be helpful to plan educational programmes involving food operators and may be an effective preventive measure, especially in settings where financial resources are lacking for the construction of adequate infrastructures.