Meta-analysis of the prevalence of the main human pathogens in vegetables, with emphasis on lettuce.

This meta-analysis aims to summarize the available information on the prevalence of the main human pathogenic microorganisms in vegetables, with emphasis on lettuce (Lactuca sativa). The database searches included scientific papers from 1980 to 2019, without language restrictions. Inclusion criteria were prevalence or incidence studies published in peer-reviewed journals reporting the total number of vegetable samples studied and the number of samples positive for the presence of the studied pathogens. The target pathogens were grouped into the following categories: bacteria, parasites and viruses. Results of different vegetable types, years of sampling, analyzed regions or species of microorganisms reported in the same article were considered as different studies. Therefore, each scientific article may contain several studies. Multilevel random-effect meta-analysis models were fitted to estimate the mean occurrence rate of pathogenic microorganisms and to compare them with different factors potentially associated with the outcome. Overall, the prevalence of bacterial, parasitic and viral pathogens in vegetables was relatively low. The mean prevalence of bacterial hazards was < 0.023, with the exception of S. aureus, whose prevalence was estimated at 0.096. The mean occurrence rates of parasites and viruses were 0.067 (95 % CI: 0.056-0.080) and 0.079 (95 % CI: 0.054-0.113), respectively. The prevalence of pathogenic E. coli and parasites increased as the year of publication of the scientific articles progressed, whereas the prevalence of the other bacterial pathogens and enteric viruses was steady. The types of vegetables evaluated did not affect pathogen prevalence. The prevalence of pathogenic microorganisms differed according to the continent of origin, except for E. coli O157:H7 and parasites. The prevalence of pathogens in vegetables is of public health importance, especially in vegetable types that are eaten raw, without thermal treatment to inactivate pathogens. This meta-analysis results show the need to apply proper sanitation methods to treat raw vegetables in order to avoid foodborne infections.

High prevalence of clade 8 Escherichia coli O157:H7 isolated from retail meat and butcher shop environment.

Escherichia coli O157:H7 is an enteric pathogen associated with food safety threats and with significant morbidity and mortality worldwide. In Argentina, post-enteric hemolytic uremic syndrome (HUS) is endemic, with >70% of cases associated with E. coli O157 infection. To date the biological basis behind the severity among E. coli O157 infections is unknown. However, single nucleotide polymorphism (SNP) typing has helped to define nine E. coli O157:H7 clades, of which clade 8 strains are associated with severe disease cases. The aim of this study was to characterize a collection of 20 STEC O157:H7 strains isolated between 2011 and 2013 from ground beef and different environmental samples from butcher shops of Argentina. All strains harbored the eae, ehxA, fliCH7, efa, iha, and toxB genes, with stx2a/stx2c as the predominant genotype (75%). The XbaI-PFGE analysis showed that the E. coli O157 strains had high genetic diversity. Nine strains were grouped in four XbaI-PFGE clusters, whereas 11 strains showed unique XbaI-PFGE patterns. In contrast, the SNP analysis allowed us to separate the strains in two distinct lineages representing clade 8 (70%) and clade 6 (30%). Our results show the molecular characterization of E. coli O157 strains isolated from ground beef and environmental samples from Argentinean butcher shops.