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
Gloria Alberto Manhique *
Laboratory of Food Microbiology and Food Control, Institute of Food Science and Technology, Federal University of Rio Grande do Sul - ICTA /UFRGS, 9500, Bento Gonçalves Avenue, building 43212, Campus do Vale, Agronomy, Porto Alegre, RS, Brazil, Faculty of Engineering and Technology, Department of Agricultural Sciences, Maputo Pedagogical University, Maputo João Raposo Beirão Street, 135, PO Box, 3276, Mozambique and Centre of Excellence in Food Security, Department of Plant and Soil Sciences, University of Pretoria, Hatfield, Pretoria 0002, South Africa.
*Author to whom correspondence should be addressed.
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.
Keywords: Ready-to-eat lettuce salads, lettuce, Escherichia coli, Lactuca sativa, food markets, food safety, hygiene conditions, shiga toxin, fresh produce, maputo.