Prevalence and genetic characteristics of Shigatoxigenic Escherichia coli from patients with diarrhoea in Maasailand, Kenya

Abstract

Shigatoxigenic Escherichia coli strains are food-borne bacterial pathogens that may cause haemorrhagic colitis (HC) in humans which can lead to life-threatening systemic complication, including haemolytic uremic syndrome (HUS).This study aimed to characterize and analyze virulence properties of pathogenic E. coli isolates among patients with diarrhoea from a Maasai community in Kenya. Stool samples from 380 patients of all ages from the Kajiado and Narok districts of Kenya were investigated for the presence of enteric bacterial pathogens by conventional and molecular methods. Bacterial diarrhoea was diagnosed in 141/380 (37.1%) cases, of which enterotoxigenic E. coli (ETEC) compromised 29.8%, shigatoxigenic E. coli (STEC) 24.1%, enteroaggregative E. coli (EAEC) 14.2%, enteroinvasive E. coli (EIEC) 12.8% and enteropathogenic E. coli (EPEC) 3.5%. Gene analysis for STEC virulence factors showed that 52.9% isolates carried stx1, 29.4% possessed stx2, 14.7% carried both stx1 and stx2, and 2.9% had stx2e. 23.5% isolates carried enterohaemolysin and 20.5% isolates possessed the Intimin gene. From 9 strains that exhibited adherence, 7 contained both Intimin and Haemolysin genes. Infections with Intimin-positive STEC strains (46%) were more frequent in patients with bloody diarrhoea, especially in children under 5 years of age, whereas Intimin-negative STEC infections dominated in adults. Although STEC infection as a cause of bloody diarrhoea has not attracted much attention as a medical problem in Kenya, our findings indicate that this is a problem that must be investigated. The 24.1% isolation rate of STEC among the Maasai is one of the highest reported rates worldwide.