Distribution of Microbial Contaminants of Minimally Processed Salads Produced in Tunisia: Need to Strengthen Good Hygiene Practices

The microbiological safety of ready-to-eat (RTE) salads is considered as a major concern due to the absence of lethal treatments during processing. In this study, we aimed to investigate the microbiological quality of RTE salads commercialized in Tunisia and to determine the antibiotic resistance of isolated pathogens, in particular Staphylococcus aureus (S. aureus). A total of 100 samples were analyzed for total aerobic bacteria, total coliforms, Escherichia coli (E. coli), yeasts and molds, Salmonella spp., Listeria monocytogenes (L. monocytogenes), and S. aureus as well as norovirus (NoV) GI and GII using specific standard methods described by the International Organization for Standardization (ISO). All samples presented unacceptable microbiological quality due to high concentrations of total aerobic bacteria and yeasts (> 106 CFU/g) and total coliforms (> 104 CFU/g). E. coli and molds were detected at unsatisfactory levels in 4% and 12% of samples, respectively. The pathogens Salmonella spp. and L. monocytogenes were not detected. S. aureus were detected at unsatisfactory levels in 6% of samples. S. aureus isolates were resistant to more than five antibiotic classes. Thus, RTE salads could be a vehicle of multiresistant S. aureus. The total prevalence of NoV GII was 2% (mean 3.81±0.30 Log GC/25 g), and no NoV GI-positive samples were identified. This study showed that the microbiological quality of RTE salads commercialized in Tunisia was unacceptable, highlighting the need to ensure good agricultural and hygiene practices from farm to fork to improve the quality and safety of these products.