Vero cytotoxin produced by Escherichia coli strains of animal origin.

A heat-labile Vero cytotoxin (VT) was detected by the Vero cell assay in the culture supernatants of ten Escherichia coli strains isolated from a variety of clinical sources. The VT titer varied with strains, ranging from 1:8 to 1:2,048. No VT was found to be cytotoxic for Y1 mouse adrenal cells or to induce fluid accumulation in the rabbit or porcine ileal loops. No strains produced a heat-labile enterotoxin as defined by either tissue culture or the standard ileal loop reaction. Three strains originated from piglets with diarrhea were confirmed by the infant mouse reaction to produce a heat-stable enterotoxin. Neutralization studies revealed antigenically the presence of two different forms of VT produced by E. coli strains of animal origin.