VIRULENCE MARKERS OF SHIGA-LIKE TOXIN-PRODUCING ESCHERICHIA-COLI STRAINS ORIGINATING FROM HEALTHY DOMESTIC-ANIMALS OF DIFFERENT SPECIES

Shiga-like toxin (verotoxin)-producing strains of Escherichia coil (SL TEC) originating from healthy cattle, sheep, goats, pigs, cats, and do gs were investigated for properties which are related to virulence of E. coil for humans. The sit-II (Shiga-like toxin II) and slt-IIc genes sere frequent in SLTEC from healthy cattle and dogs but were rarely f ound in SLTEC from other animals. The slt-IIe gene was detected only i n porcine SLTEC. SLTEC from goats and SLTEC from sheep were found to c arry different SLT-II determinants which were not further characterize d genetically, Sixty (28.8%) of 208 SLTEC from healthy animals showed diffuse adherence to HEp-2 cells. However, none of the strains was pos itive for genes specific for the local adherence (eaf), diffuse adhere nce (daa), or enteroaggregative (EAggEC) E. coil type. Only 3 (1.4%) o f the 208 SLTEC were positive for attaching and effacing E. coil (eae) sequences. The enterohemolytic phenotype was present in 128 of the 20 8 SLTEC, Almost all enterohemolytic animal SLTEC were found to carry D NA sequences specific for the plasmid-encoded enterohemorrhagic E. col i hemolysin of E. coli O157. Bacteriophage-associated enterohemolysin (Ehly1 and Ehly2)-specific sequences were detected only in 14.4% of th e 208 SLTEC and were linked with certain serotypes. The SLTEC from hea lthy animals constitute a very heterogeneous group of E. coil, and man y of these strains appeared to be specific for their hosts. The absenc e of eae sequences in most animal SLTEC could indicate that these stra ins are less virulent for humans than the classical eae-positive enter ohemorrhagic E. coli types.