Role of the eaeA gene in experimental enteropathogenic Escherichia coli infection.

Abstract

Enteropathogenic Escherichia coli (EPEC) infections are a leading cause of infant diarrhea in developing countries. Recently eaeA, a gene necessary for the characteristic intimate attachment of EPEC to epithelial cells in tissue culture, was described. We conducted a randomized, double-blind study to determine the role of the eaeA gene in human EPEC infection. 11 adult volunteers ingested 2 X 1010 colony-forming units of 0127:H6 EPEC strain E2348/69, and an equal number received the same dose of an isogenic eaeA deletion mutant constructed from E2348/69. Volunteers were monitored for the development of diarrhea, fever, and systemic and gastrointestinal complaints. Diarrhea developed in all 11 volunteers who received E2348 /69 and in 4 of 11 who received the mutant (P = 0.002). Fever was more common in recipients of the wildtype strain (P = 0.024). Stool volumes were lower in recipients of the mutant. All volunteers seroconverted to E2348 /69 LPS, but the geometric mean peak titers of serum IgG and IgA in recipients of the mutant were lower than those of recipients of the wild-type strain. IgA against LPS was detected in the jejunal fluid of six of six recipients of E2348 /69 and 5/6 recipients of the mutant. This study unambiguously assigns a role for eaeA as an EPEC virulence gene, but the residual diarrhea seen in recipients of the mutant indicates that other factors are in-

In Vitro and In Vivo Model Systems for Studying Enteropathogenic Escherichia coli Infections

“…Intestinal biopsies taken from human volunteers infected with wild-type EPEC show destruction of the epithelial brush border (Tacket et al 2000), a phenotype that is reproducible in tissue culture (Knutton et al 1987). All but one individual developed diarrhea after consumption of the wild-type strain (Tacket et al 2000), whereas only one instance of diarrhea occurred in 10 individuals who consumed the espB mutant (Tacket et al 2000) and four out of 11 who consumed the intimin mutant (Donnenberg et al 1993). Due to the relative inability of most EPEC strains to colonize nonhuman hosts and cause diarrhea, clinical trials using adult volunteers are important to further our knowledge of EPEC pathogenesis in humans and to determine the role of specific virulence factors in EPEC-mediated disease (Tacket et al 2000).…”

“…Adult volunteers have been used to verify the roles of intimin, EspB, and bundle-forming pili (BFP) in EPEC pathogenesis (Donnenberg et al 1993;Bieber et al 1998;Tacket et al 2000). BFP is an EPEC-specific virulence factor but intimin and EspB are found in the genomes of diverse A/E pathogen species (Tauschek et al 2002;Iguchi et al 2009;Ogura et al 2009;Petty et al 2010).…”

“…Due to the relative inability of most EPEC strains to colonize nonhuman hosts and cause diarrhea, clinical trials using adult volunteers are important to further our knowledge of EPEC pathogenesis in humans and to determine the role of specific virulence factors in EPEC-mediated disease (Tacket et al 2000). However, the use of human volunteer studies is not without its drawbacks as the diarrhea that develops is often not reproducible (Donnenberg et al 1993) and susceptibility among individual hosts is likely to vary based on differences in immune response and prior exposure to the pathogen. Additionally, the tendency for EPEC and EHEC to infect and cause disease in young children (Kaper et al 2004) and the varying degree of disease severity associated with EHEC infections (Nataro and Kaper 1998) precludes the use of appropriate volunteer populations, thus making the identification of host resistance genes difficult.…”

Identification of the intimin-binding domain of Tir of enteropathogenic Escherichia coli

“…Intimin is a 94 kDa outer membrane protein encoded by eae (Jerse and Kaper, 1991) and is a member of the invasin/intimin-like protein family. Intimin mutants can activate some signalling in the host cell, inducing tyrosine phosphorylation of Tir and generalized actin accumulation, but they cannot focus actin into pedestal-like structures (Donnenberg and Kaper, 1991;Rosenshine et al, 1992;Donnenberg et al, 1993a). Intimin is required for A /E lesion formation and for complete virulence in humans and animals.…”

The role of epithelial malfunction in the pathogenesis of enteropathogenic E. coli-induced diarrhea

“…14,15 However, EPEC-induced diarrheal symptoms occur before the full formation of A/E lesions. 16 Therefore, although the formation of A/E lesions and the diffuse loss of brush border surface area certainly exacerbate diarrhea, they are unlikely to be the leading mechanisms in its initiation. Instead, a more active secretory mechanism is suspected to mediate the rapid development of initial diarrheal symptoms.…”