Clonal Relatedness of Enterotoxigenic Escherichia coli Strains Isolated from a Cohort of Young Children in Guinea-Bissau

Abstract

In a cohort study of 200 young children in Guinea-Bissau, it was previously found that some enterotoxigenic Escherichia coli (ETEC) strains were more pathogenic than others, depending on the type of toxin that they could produce, and that natural ETEC infections induced substantial protection against new infections with ETEC strains that had the same combination of toxins and colonization factors (CFs). We wanted to describe the clonal relatedness of the ETEC strains isolated during this study and to investigate whether the protective antigens and the virulence factors that were responsible for the pathogenic traits were common to strains that were clonally closely related or whether they were more likely to be encoded by the ETEC virulence plasmids that normally encode the toxins and the CFs. By performing repetitive sequence-based PCR analysis of strains representing 452 infections, we found that strains that had the same toxin-CF profile were usually closely related, although a few were unrelated. Strains that did not have the same toxin-CF profiles but that were positive for a given toxin or for a given CF were not consistently more closely related to each other than to strains that were negative for the same toxin or CF. Our results indicate that the pathogenic traits of ETEC were mainly attributed to genes carried on the ETEC virulence plasmids. Because most strains that had the same toxin-CF profile were closely related, it seems likely that the toxin-CF-specific protection was clonal and was not targeting antigens encoded by the virulence plasmids. These results are of relevance to the ETEC vaccine development effort.

Diarrheagenic Escherichia coli in sub-Saharan Africa: Status, Uncertainties and Necessities

“…However, a large US nursery outbreak in 1974-75 was attributed to STproducing ETEC [92] and shortly after, Levine et al [93] demonstrated that strains producing ST alone were capable of eliciting diarrhea, nausea, vomiting and abdominal cramps in adult volunteers. This finding is backed by epidemiological evidence, including controlled studies performed in different parts of Africa, which suggest that ST-producing ETEC are more strongly associated with childhood diarrhea than are LT-producing strains, even though the latter may be more common overall [41,65,91,94]. The same may also be true for travellers' diarrhea [95].…”

“…CFA/IV is typically comprised of CS6 with CS5 or CS4. Steinsland et al [94] sought to determine the role of ETEC in infantile diarrhea and to identify predominant CFAs in Guinea-Bissau.…”

Molecular Characterization of Diarrheagenic Escherichia coli from Libya

“…They found STp and STh genotypes in 37% (17 of 46) and in 63% (29 of 46), respectively. On the other hand, Steinsland and others 36 in Guinea-Bissau, examined the prevalence of ETEC in young children by PCR detection, reported that only ETEC strains producing STh alone or in combination with LT, but not STp-producing strains, were associated with diarrhea. Identification of ETEC from diarrheic children using PCR or ELISA has not been reported previously from Libya.…”

Construction of Bifidobacterium infantis as a live oral vaccine that expresses antigens of the major fimbrial subunit (CfaB) and the B subunit of heat-labile enterotoxin (LTB) from enterotoxigenic Escherichia coli

“…Due to the presence of CFAs on the bacterial surface, CFAs may be advantageous as antigenic targets for inducing a prolonged mucosal immune response to ETEC, if incorporated in a vaccine (Girard et al, 2006;Steinsland et al, 2002). Therefore, oral administration of a live ETEC vaccine may be more effective than a killed vaccine, although this is currently debatable.…”