Metabolic and genetic profiling of clinical O157 and non-O157 Shiga-toxin-producing Escherichia coli

Abstract

A collection of clinical Shiga-toxin-producing Escherichia coli (STEC) strains, mainly belonging to serotypes O26, O103, O111, O145 and O157, was characterised by a polyphasic approach including molecular serotyping, PCR-based detection of virulence factors (stx1, stx2, eae, EHEC-hlyA, saa, katP, espP), carbohydrate fermentation profiles using API50 tests and random amplification of polymorphic DNA (RAPD) fingerprinting. An RAPD protocol based on the combination of 2 primers resulted in sufficiently complex patterns enabling discrimination to the serotype level. Moreover, carbohydrate fermentation profiles obtained after evaluating up to 50 different carbohydrates led to separation of different STEC serotypes. Virulence typing results confirm the association of Shiga toxins and intimin subtypes with specific serotypes and clinical diagnosis. Clinical diagnosis of strains did not correlate with either RAPD profiles or carbohydrate fermentation patterns.