Evaluation of a vero cell toxicity test to detect EHEC infection

An epidemiologic investigation was carried out in Modena (Italy) to evaluate the prevalence of faecal VEROtoxin (FVT) in diarrhoeal stool specimens. One thousand and sixty-six stool specimens, submitted to the Clinical Microbiology Laboratory of the University Hospital of Modena, were collected and faecal filtrates tested for neutralizable cytotoxin by a toxicity test on VERO cells. Cytopathic effect on VERO cells was produced by 301 stool specimens (28%); neutralizable VT was detected in 40 (13%) out of 301 positive samples (3.7% of 1066 specimens). The prevalent FVT type was VT2 (50%), followed by VT1 (32.5%) and VT1+2 (17.5%). We evaluated an assay that detects both VTs directly from stool specimens to demonstrate that enterohemorrhagic strains (EHEC) should be considerated a causative agent of sporadic non-bloody diarrhoea. Our results suggest that toxin neutralization assay is a sensitive and specific technique and may be used as an alternative method to diagnose diarrhoeal infections caused by EHEC.