[Characteristic of verotoxigenic strains of Escherichia coli]

The aim of the study was the isolation from faecal samples of patients with diarrhoea of verotoxigenic strains of E. coli (VTEC) on the basis of characteristic biochemical properties and production of enterohaemolysin and comparison of isolated verotoxigenic strains with reference strains of VTEC. For isolation of VTEC from 257 stool samples derived from patients with diarrhoea were used selective medium sorbiol--Mac Conkey agar (SMAC) and media supplemented with unwashed and washed in PBS sheep erythrocytes for detection of haemolysins of E. coli. In all haemolytic and sorbitolo-positive or -negative strains isolated from 93 stool samples were examined the activity of beta-glucuronidase using MUG (4-methylumbelliferyl-beta-D-glukuronid) as a substrate for that enzyme. All isolated haemolytic strains as well as reference VTEC were examined on Vero cell line. Verotoxigenic strains from examined samples were investigated by agglutination assay with antiserum to E. coli O157 and then with antisera to eneropathogenic E. coli (EPEC). After that they were examined with ID GN and ATB GN tests. In 93 (36.2%) examined samples there were haemolytic strains of E. coli which fermented or not sorbitol and were MUG-positive or negative. Only in 2 (0.2%) stool samples there were verotoxigenic strains of E. coli which were sorbiol-positive and MG-positive. Both strains belonged to O26 serotype and were derived from samples of two children with diarrhoea. Isolated verotoxigenic strains of E. coli O26 were susceptible on all tested antibiotics.