T8-02 Enteroaggregative Escherichia coli:  Predominant Diarrheagenic Escherichia coli Pathotype among Irrigation Water and Food Sources

Tuesday, July 11, 2017: 1:45 PM
Room 16 (Tampa Convention Center)
Matthew Aijuka , University of Pretoria , Pretoria , South Africa
Araceli Santiago , University of Virginia , Charlottesville , VA
Jorge Girón , University of Virginia , Charlottsville , VA
James Nataro , University of Virginia School of Medicine , Charlottesville , VA
Elna Buys , University of Pretoria , Pretoria , South Africa
Introduction:  Diarrheagenic Escherichia coli (DEC) has been implicated in foodborne outbreaks worldwide and have been associated with childhood stunting in the absence of diarrhea. Infection is common, but the routes of transmission have not been determined.

Purpose: This study was undertaken to determine the most prevalent pathotypes, as well as associated foods and environmental sources. The information gathered will help to provide better guidance to various stakeholders in ensuring food safety and public health.

Methods:  PCR, partial gene sequencing, and cell adherence were used to characterize 205 E. coli strains, previously isolated from milk (118), irrigation water (48), irrigated lettuce (29), and coleslaw (10) in South Africa. The results of the characterization were used to group the strains, based on four diarrheagenic E. coli pathotypes; enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC) and diffusely adherent E. coli (DAEC).

Results: Using a combination of molecular and phenotypic assays, only EAEC (37%, 17 of 46) and EIEC (4.3%, 2 of 46) were identified in the samples. PCR and partial gene sequencing initially confirmed EAEC (2.4%, 5 of 205) virulence gene determinants (aatA and aaiC) as the only pathotype. Phylogenetic analysis based on identity of aatA and aaiC genes, in strains from this study to those in Genbank, showed close relatedness to foodborne and uropathogenic strains. Human strains clustered differently from environmental strains, suggesting a potential role for use of virulence gene determinants in source tracking.

Significance:   EAEC may be the leading cause of food- and waterborne enteric infection in South Africa. Additionally, sole use of molecular based methods targeting virulence gene determinants may underestimate numbers, especially among heterogeneous pathogens such as EAEC.