Genomic Characterization of Enteroaggregative Escherichia coli From Children in Mali

Abstract

Background. Enteroaggregative Escherichia coli (EAEC) is a cause of epidemic and sporadic diarrhea, yet its role as an enteric pathogen is not fully understood.Methods. We characterized 121 EAEC strains isolated in 2008 as part of a case-control study of moderate to severe acute diarrhea among children 0–59 months of age in Bamako, Mali. We applied multiplex polymerase chain reaction and comparative genome hybridization to identify potential virulence factors among the EAEC strains, coupled with classification and regression tree modeling to reveal combinations of factors most strongly associated with illness.Results. The gene encoding the autotransporter protease SepA, originally described in Shigella species, was most strongly associated with diarrhea among the EAEC strains tested (odds ratio, 5.6 [95% confidence interval, 1.92–16.17]; P = .0006). In addition, we identified 3 gene combinations correlated with diarrhea: (1) a clonal group positive for sepA and a putative hemolysin; (2) a group harboring the EAST-1 enterotoxin and the flagellar type H33 but no other previously identified EAEC virulence factor; and (3) a group carrying several of the typical EAEC virulence genes.Conclusion. Our data suggest that only a subset of EAEC strains are pathogenic in Mali and suggest that sepA may serve as a valuable marker for the most virulent isolates.

Distribution and Molecular Characterization of Enteroaggregative Escherichia coli Isolated from Children in A Case-control Study of Acute Diarrhea in Thailand

“…The frequency of adherence fimbria type I-AAF/I (aggA) was the greatest among EAEC isolates from both cases and controls, followed by AAF/III (agg3A), AAF/II (aafA), and AAF/IV (agg4A). These findings were similar to other studies [28,29] where nearly half of clinical EAEC isolates do not possess known major fimbria subunits.…”

“…Previous studies suggested that sepA is a valuable identification marker for virulent EAEC [18,29]. This study identified less distribution of sepA in EAEC isolates from Thailand compared to previous studies [28,29]. Therefore, the contribution of sepA to EAEC virulence should not be overlooked.…”

“…EAEC toxins include serine protease autotransporters of the Enterobacteriaceae (SPATEs) [26,27]. The SPATEs pic and sepA were linked to EAEC pathogenesis [28,29]. Other toxins, to include Shigella enterotoxin (ShET1) and heat stable toxin (EAST-1), were also associated with EAEC diarrhea [30,31].…”

Phenotypic and Molecular Characterization of Enteroaggregative <i>Escherichia coli</i> Isolated in Kawasaki, Japan

“…Therefore, we infer the importance of evaluating the grade according to the thickness of the scum layer formed. Results show that 65 (26 strains) harbored one of the AAF genes, which indicates that the frequency of EAEC strains harboring AAF genes in our study is higher than that found in other countries (22,25). The classification of aggR-positive E. coli as EAEC in this study might have contributed to this high figure.…”

“…All isolated EAEC strains were examined for the presence of pCVD432, astA, and 4 AAF encoding genes (aggA, aafA, agg3A, and agg4A) using the primers described in Table 1 (13,20,21,22). The aggA, aafA, agg3A, and agg4A genes respectively encode AAF I, AAF II, AAF III, and AAF IV.…”