Quantitative Microbiological Risk Assessment of Two Street Foods Sold in a Kenyan Town with Regard to Salmonella Contamination

Abstract

Street sold foods have gained popularity in recent times, particularly in developing countries where their sale is often unregulated, hence, has a potential to transmitting pathogenic microorganisms which are of public health concern. A survey of two street foods, kachumbari (a type of a vegetable salad) and mandazi (a type of a wheat-based flour snack) was carried out in a Kenyan town to determine the prevalence and conduct a quantitative microbiological risk assessment to estimate the risks of infection due to consumption of the two products contaminated with Salmonella. A prevalence of 19% (16 out of 86 samples) and 7% (6 out of 86 samples) was observed for kachumbari and mandazi respectively. A risk assessment model composed of three different steps (nodes) comprising finished product (processed ready-to-eat), waiting (storage) period and consumption was used for the microbiological risk assessment. Models built in excel spreadsheets using @Risk software package, version 6 (Palisade USA) was used to obtain the inputs, outputs, and run the Monte Carlo simulations at 5000 iterations. The model estimated that in 95% of the cases, the consumers of kachumbari would be exposed to a maximum dose of 8.30 x 104 Salmonella cells per single serving. On the other hand, in 95% of the cases, consumers of mandazi would be exposed to a maximum dose of 4.0 x 104 Salmonella cells per single serving. The model also predicted that 64.3% and 69% of the population was at risk of developing salmonellosis upon consumption of contaminated kachumbari and mandazi respectively. The results indicate that these two products can contribute to high levels of salmonellosis morbidity. Nevertheless, a significant reduction in the level of ingested Salmonella cells in kachumbari and mandazi could be attained through a reduction of the prevalence of the pathogen contamination at or before the point of sale by the employment of good hygienic practices during their preparation and subsequent handling, in addition to enforcement of food hygiene regulations regarding street foods to ensure microbiologically safe foods are sold to the consumers. In order to improve the accuracy of this risk assessment model, more data, whenever available should be used in such studies.