Molecular characterization of virulence factors in diarrhoeagenic Escherichia coli isolates from children in Nairobi, Kenya

Introduction: Among the bacterial causes, diarrheagenic Escherichia coli (DEC) is the most important etiologic agent of childhood diarrhoea and represents a major public health problem in developing countries. New evidence suggests that major differences in virulence among groups of DEC pathotypes may be related to the presence of specific pathogenicity islands (PAIs). Methodology: Multiplex and conventional PCR assays were used to identify the DEC pathotypes and PAIs respectively from 207 E. coli isolates. Results: The predominant DEC pathotype isolated was EPEC 19.3% (40/207), followed by ETEC 7.25% (15/207), EAEC 3.86% (8/207), STEC 0.97% (2/207) and EIEC 0.48% (1/207). The PAIs detected were enteropathogenic secreted protein C (EspC) 12.2% (8/66), locus of enterocyte effacement (LEE) 62.1% (41/66), and high pathogenicity island (HPI) 57.6% (38/66). Six percent (4/66) expressed only fyuA gene, 12.2% (8/66) irp2 only, and 39.4% (26/66) expressed both fyuA and irp2 genes. SHI-2 39.4% (26/66), she 6% (4/66) and O island 33.3% (22/66), 19.8% (13/66) expressed only efa/lifA gene, 7.6% (5/66) pagC gene only and 6.1% (4/66) expressed both efa/lifA and pagC genes. Toxigenic invasion A (TIA) PAI was not detected. Conclusion: This study revealed that in addition to eaeA, stx, aat, einv, st and lt virulence genes exhibited in the different DEC pathotypes there are numerous PAIs in the DEC pathotypes. The PAIs can increase gene mobility within various motile elements, which has implications for the spread of virulence factors from DEC to commensal E. coli.