Enteroaggregative Escherichia coli is the predominant diarrheagenic E. coli pathotype among irrigation water and food sources in South Africa

Abstract

Diarrheagenic E. coli (DEC) has been implicated in foodborne outbreaks worldwide and have been associated with childhood stunting in the absence of diarrhoea. Infection is extraordinarily common, but the routes of transmission have not been determined. Therefore, determining the most prevalent pathotypes in food and environmental sources may help provide better guidance to various stakeholders in ensuring food safety and public health and advancing understanding of the epidemiology of enteric disease. We characterized 205 E. coli strains previously isolated from producer distributor bulk milk (PDBM)(118), irrigation water (48), irrigated lettuce (29) and street vendor coleslaw (10) in South Africa. Enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC) and diffusely adherent E. coli (DAEC) were sought. We used PCR and partial gene sequencing for all 205 strains while 46 out of 205 that showed poor resolution were subsequently characterized using cell adherence (HeLa cells). PCR and partial gene sequencing of aatA and/or aaiC genes confirmed EAEC (2%, 5 out of 205) as the only pathotype. Phylogenetic analysis of sequenced EAEC strains with E. coli strains in GenBank showing ≥80% nucleotide sequence similarity based on possession of aaiC and aatA generated distinct clusters of strains separated predominantly based on their source of isolation (food source or human stool) suggesting a potential role of virulence genes in source tracking. EAEC 24%, 11 out of 46 strains (PDBM = 15%, irrigation water = 7%, irrigated lettuce = 2%) was similarly the predominant pathotype followed by strains showing invasiveness to HeLa cells, 4%, 2 out of 46 (PDBM = 2%, irrigated lettuce = 2%), among stains characterized using cell adherence. Therefore, EAEC may be the leading cause of DEC associated food and water-borne enteric infection in South Africa. Additionally, solely using molecular based methods targeting virulence gene determinants may underestimate prevalence, especially among heterogeneous pathogens such as EAEC.

Carbapenem Resistance Profiles of Pathogenic Escherichia coli in Uganda

“…This correlates well with studies conducted outside the African content [56,57]. In contrast, similar studies carried out in sub-Saharan Africa (Tanzania, South Africa and Mozambique) reported EAEC as the most prevalent DEC pathotype [58][59][60][61][62] yet it was not detected in this study. As expected, DEC were predominantly isolated from Anal/fecal swabs.…”

Carbapenem resistance profiles of Pathogenic Escherichia coli in Uganda

“…This correlates well with studies conducted outside the African content[51,52]. In contrast, similar studies carried out in sub-Saharan Africa (Tanzania, South Africa and Mozambique) reported EAEC as the most prevalent DEC pathotype[53][54][55][56][57] yet it was not detected in this study. As expected, DEC were predominantly isolated from Anal/fecal swabs.…”

High prevalence of multidrug resistant Escherichia coli isolated from fresh vegetables sold by selected formal and informal traders in the most densely populated Province of South Africa

“…Members of this family, that is, Escherichia coli and Salmonella spp., have often been associated with foodborne bacterial outbreaks following raw fresh produce consumption (Tope, Hitter, & Patel, 2016). This includes diarrheagenic E. coli strains, including enteropathogenic (EPEC), enterotoxigenic (ETEC), enterohaemorrhagic (EHEC), enteroaggregative (EAEC), and enteroinvasive (EIEC) E. coli in foodborne disease outbreaks (Aijuka, Santiago, Girón, Nataro, & Buys, 2018; Canizalez‐Roman et al., 2019). In addition to generic E. coli , diarrheagenic strains are also found in the intestinal tracts of mammals and are therefore often used as indicators of fecal contamination in fresh produce supply chains (Denis et al., 2016).…”