Prevalence of Escherichia coli in Lettuce (Lactuca sativa) and Ready-to-Eat Lettuce Salads in Maputo Food Markets and the Observation of Hygiene Conditions: A Preliminary Study

Abstract

Knowledge of the microbiological quality of lettuce and ready-to-eat lettuce salads vended in food markets in Maputo, Mozambique, remains limited. This study evaluated the microbial quality and the presence of generic Escherichia coli and Shiga toxin-associated genes (stx1F, stx1R, stx2F and stx2R) in two sample matrices, lettuce and ready-to-eat lettuce salad, vended in five food markets in Maputo. A total of 70 samples (35 lettuce samples and 35 ready-to-eat lettuce salad samples) were collected and analysed using standard plating techniques. Environmental and operating conditions in the five food markets were also assessed using a questionnaire. The results showed that Escherichia was the predominant genus in ready-to-eat salad and lettuce samples, with Escherichia coli (17.14%) and Escherichia hermannii (8.57%) being the dominant species isolated from ready-to-eat lettuce salads. No Shiga toxin-associated genes were detected by polymerase chain reaction (PCR) in the Escherichia spp. identified in ready-to-eat salads. Across the five food markets sampled, only 25.5% of vendors had access to clean water near the food preparation site, and 49.1% of sanitary facilities were poor. This preliminary study highlights the relevance of lettuce salads as potential sources of E. coli contamination when hygiene conditions are inadequate.