Characterization of shiga toxin-producing Escherichia coli strains isolated from calves in Poland

Fecal samples from 67 3-5-months-old calves with diarrhea were screened for the presence of shiga toxin-producing Escherichia coli (STEC). Several acc essory virulence factors genes were also tested. Among 192 E.coli isolates tested, 15 (7.6%) were found to harbour the shiga toxin 1 or 2 (stx1 or stx 2) genes. The stx2-carrying samples were further subtyped by PCR for the st x2c, stx2d, and stx2e toxin variants. It was shown that stx2-positive bacte ria mainly possessed the stx2e shiga toxin type gene. The enterohemolysin ( hlyA) and intimin (ene) genes were found in seven (46.7%) STEC strains wher eas the cytotoxic necrotizin factor 1 and 2 or the P fimbrial genes were de tected in two isolates only. This study confirmed that calves are a reservo ir of STEC strains (with all pathogenicity genes) that may be virulent for humans. (C) 2000 Elsevier Science Ltd. All rights reserved.