Genotypic and phenotypic analysis of diarrheagenic Escherichia coli strains isolated from Brazilian children living in low socioeconomic level communities

Diego M Lozer,Tamara B Souza,Mariane V Monfardini,Isabel C A Scaletsky,Sônia S Kitagawa,Fernando Vicentini,Liliana C Spano

doi:10.1186/1471-2334-13-418

Abstract

BackgroundChildhood diarrheal diseases remain highly endemic in developing areas of Brazil. The importance of Escherichia coli among children with diarrhea in these areas was unknown. This study determined the prevalence of different E. coli categories in symptomatic and asymptomatic children from low socioeconomic level rural communities in southeastern Brazil.MethodsA total of 560 stool samples were collected from 141 children with diarrhea (< 10 years) and 419 apparently healthy controls who resided in 23 communities. E. coli isolates (n = 1943) were subjected to two multiplex PCRs developed for the detection of enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), diffusely adherent E. coli (DAEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), and Shiga toxin-producing E. coli (STEC). Strains were also examined for the presence of EPEC, EAEC, and DAEC by assays of adhesion to HEp-2 cells and by hybridization with specific DNA probes.ResultsDiarrheagenic E. coli strains were isolated from 253 (45.2%) children, and were associated with diarrhea in children aged < 5 years (p < 0.001). EAEC (20.9%), DAEC (11.6%), EPEC (9.3%) were the most frequent pathotypes, followed by ETEC (2.7%), EIEC (0.5%), and STEC (0.2%). Depending of the assay, EPEC, EAEC, and DAEC (collectively termed enteroadherent E. coli) strains were isolated in 45% to 56% of diarrhea cases, a significantly higher incidence than in controls (P < 0.05). Individually, only DAEC showed significant association with diarrhea (p < 0.05), particularly in children aged 2–5 years.ConclusionThis study indicates that enteroadherent E. coli is an important cause of diarrhea in children living in low socioeconomic level communities in southeastern Brazil. Our results reveal that the PCR1 assay is an excellent tool for the identification of EAEC and DAEC.

Highlights

Childhood diarrheal diseases remain highly endemic in developing areas of Brazil
Diarrheagenic E. coli strains were isolated from 253 (45.2%) children, and were associated with diarrhea in children aged < 5 years (p < 0.001)
The present study was performed to determine the prevalence of different diarrheagenic Escherichia coli categories in symptomatic and asymptomatic children living in low socioeconomic rural communities in southeastern Brazil

Summary

Introduction

Childhood diarrheal diseases remain highly endemic in developing areas of Brazil. Diarrheal disease remains a major public health problem in developing countries, and is responsible for high morbidity and mortality among children under 5 years [1,2]. Diarrheagenic E. coli (DEC) strains can be divided into six main categories on the basis of distinct epidemiological and clinical features, and specific virulence determinants [4]: enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli (EHEC) or Shiga-toxin producing E. coli (STEC), enteroaggregative E. coli (EAEC), and diffusely adherent E. coli (DAEC). In order to diagnosis, we set up a two-reaction multiplex PCR assay for the detection of EPEC, EAEC, DAEC, ETEC, EIEC, and STEC, but so far has not been used in field studies [5]

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