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In 1982, enterohaemorrhagic Escherichia coli (EHEC) was first associated with severe disease in humans in North America. Among EHEC, E. coli O157:H7 is the classical serotype linked to serious outbreaks and sporadic cases of enterohaemorrhagic diseases such as haemorrhagic colitis and haemolytic uraemic syndrome. These strains of E. coli produce potent cytotoxins similar to Shiga toxin produced by Shigella species responsible for dysentery. There is reason to believe that currently available techniques can be improved with regard to the qualitative and quantitative isolation of E. coli O157:H7, particularly from water and food which generally contain these pathogens in low numbers. Molecular techniques for the genetic characterization of E. coli O157:H7 can be improved, particularly with regard to cost, reliability, accuracy, and genetic diversity. Determining the prevalence of E. coli O157:H7 in water sources and animal reservoirs such as cattle and pigs will cast valuable light on the epidemiology of the pathogens in South Africa. The work is particularly important in South Africa because low socio-economic communities, which live in close contact with animal carriers, are at highest risk of E. coli O157:H7 infections. E. coli O157:H7 colonies (incubated on CT-SMAC agar) carrying the genes coding for Stx2 were isolated from 1 sewage sample (0.76% of positive samples), 8 cattle faecal samples (16.67% of positive samples) and 2 pig faecal samples (14.28% of positive samples). Characterization of E. coli O157:H7 was performed by repetitive sequence analysis using ERIC-PCR to determine the relationships between the individual E. coli O157:H7 strains. The ERIC-PCR analysis of 31 E. coli O157:H7 strains revealed two distinct sections with two groups in each section. Electron microscopic analysis revealed, for the first time in South Africa, that Stx2- converting phages induced from E. coli O157:H7 have different morphologies to that of phage lambda which was previously described. Available information confirms that research on these phages which carry the genetic elements for the production of toxins by E. coli , is essential. A better understanding of these phages is likely to hold the key to the control of E. coli pathogens and a number of other pathogens. Includes 28 references, tables, figure.

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Edition: Vol. - No. Published: 09/22/2002 Number of Pages: 9File Size: 1 file , 200 KB