Summary auto-generated
This study investigated the clonal status of 94 enteropathogenic Escherichia coli (EPEC) isolates from case-control studies of childhood diarrhea in Bangladesh conducted in 1991-1994. Researchers characterized the strains using serogrouping, enterobacterial repetitive intergenic consensus (ERIC) PCR, and biochemical fingerprinting (Phene Plate system). Two dominant serogroups were identified: O114 (19 isolates) and O127 (23 isolates). Most O114 strains shared the same clonal profile. Among O127 strains, 16 produced cytolethal distending toxin (CDT) and 7 did not; both types showed high biochemical homogeneity and belonged to closely related clonal groups. The CDT-positive strains likely evolved from CDT-negative ancestors by acquiring the cdt gene. Thirty-one O antigen non-typable (ONT) strains and 21 strains from other serogroups were highly diverse with multiple clonal groups. High agreement was observed between the typing methods, particularly between biochemical and PCR typing (99-100% for major serogroups). The findings indicate that two dominant clonal groups of EPEC, predominantly O114 and O127, are responsible for most EPEC-associated childhood diarrhea in Bangladesh.
Key findings
- Two clonal groups of EPEC serogroups O114 and O127 are predominantly responsible for childhood diarrhea in Bangladesh, with high biochemical homogeneity within each group
- CDT-positive O127 strains likely evolved from CDT-negative strains of the same serogroup through acquisition of virulence genes
- A large proportion of O antigen non-typable (ONT) EPEC strains were identified with highly diverse clonal profiles, possibly representing normal flora that acquired EPEC virulence determinants
- High agreement between biochemical fingerprinting and PCR typing methods (99-100%) validates both techniques for epidemiological EPEC classification
- Most O114 strains (16 of 19) shared identical clonal profiles, suggesting a common origin and limited genetic diversity within this serogroup
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Abstract
Recent case-control studies in Bangladesh showed a high prevalence of enteropathogenic Escherichia coli (EPEC) strains (identified by DNA probes for virulence genes) associated with childhood diarrhoea. However, the clonal status of these strains is not known. A total of 94 EPEC isolates from 80 children with diarrhoea and 14 healthy matched controls isolated during 19911992 and 19931994 was characterised by serogrouping, enterobacterial repetitive intergenic consensus sequence PCR, and by a biochemical fingerprinting method (the phene plate or PhP system). Twelve O serogroups were found with O114 (n = 19) and O127 (n = 23) being the dominant serogroups. Most strains of O114 belonged to the same PhP/ PCR types. Strains of O127 contained 16 that produced cytolethal distending toxin (CDT) and seven that did not; both were found among patients as well as controls. Results of PCR and PhP typing showed that CDT-positive strains belonged to the same clonal group and were related to one of the two PhP/ PCR types of CDT-negative O127 strains. Thirty-one EPEC strains were O non-typable and 21 strains belonged to other less prevalent serogroups. These strains belonged to diverse PhP/ PCR types and did not show any similarity to the strains of two major serogroups, O114 and O127. The results suggest that two clonal groups of EPEC strains are predominantly associated with childhood diarrhoea in Bangladesh.