Isolation and characterization of verocytotoxin-producing Escherichia coliO157 from slaughter pigs and poultry

Rectal contents and tonsils from Dutch slaughter pigs collected immediately after slaughter were examined for the presence of verocytotoxin (VT)-produ cing Escherichia coli (VTEC) of serogroup O157 (O157 VTEC). In addition, fr esh fecal material from poultry layer flocks and turkey flocks collected on poultry farms was examined for the presence of O157 VTEC. E. coli O157 str ains were isolated from two (1.4%) of 145 pigs. The strains were isolated f rom samples of rectal contents, all samples of tonsils being negative. Whil e all 501 fecal samples from chicken flocks were found negative, E. coli O1 57 strains were isolated from six (1.3%) of 459 pooled fecal samples from t urkey flocks. One of the porcine isolates and one of the turkey isolates co ntained the VT2 gene, the E. coli attaching-and-effacing gene, as well as t he enterohemorrhagic E. coli hemolysin gene. Production of VT was confirmed by cytotoxicity tests on Vero cells. Based on these characteristics, the t wo stains were regarded as potentially pathogenic for humans. The porcine a nd the turkey isolate were further characterized as being of phage types 4 and 14, respectively. While biochemically typical of E. coli O157, the rema ining six isolates were nonverocytotoxigenic and negative for both the E. c oli attaching-and-effacing gene and the enterohemorrhagic E. call hemolysin gene. All eight E. coli O157 isolates did not carry genes that encode E. c oli heat-labile and heat-stable enterotoxins. It was concluded that pigs an d poultry can be a source of O157 VTEC strains characteristic of those caus ing illness in man. The extent to which pigs and poultry play a role in the epidemiology of human O157 VTEC infection needs further research. (C) 1999 Elsevier Science B.V. All rights reserved.