Isolation of a lysogenic bacteriophage carrying the stx(1ox3) gene, which is closely associated with Shiga toxin-producing Escherichia coli strains from sheep and humans

A specific PCR for the detection of a variant of the gene encoding Shiga to xin 1 (stx(1)) called stx(1OX3) (GenBank accession no. Z36901) was develope d. The PCR was used to investigate 148 Stx(1)-producing Escherichia coli st rains from human patients (n = 72), cattle (n = 27), sheep (n = 48), and a goat (n = 1) for the presence of the six, 3 gene. The stx(1OX3) gene was pr esent in 38 Shiga toxin-producing E. coli (STEC) strains from sheep belongi ng to serogroups O5, O125, O128, O146, and OX3 but was absent from Stx(1)-p ositive ovine STEC O91 strains. The stx(1OX3) gene was also detected in 22 STEC strains from humans with nonbloody diarrhea and from asymptomatic excr eters. Serotypes O146:H21 and O128:H2 were most frequently associated with stx(1OX3)- carrying STEC from sheep and humans. In contrast, Stx(1)-produci ng STEC strains from cattle and goats and 50 STEC strains from humans were all negative for the stx(1OX3) gene. The stx(1OX3)-negative strains belonge d to 13 serotypes which were different from those of the stx(1OX3)-positive STEC strains. Moreover, the stx(1OX3) gene was not associated with STEC be longing to enterohemorrhagic E. coli (EHEC) serogroups O26, O103, O111, O11 8, O145, and O157. A bacteriophage carrying the stx(1OX3) gene (phage 6220) was isolated from a human STEC O146:H21 strain. The phage was able to lyso genize laboratory E. coli K-12 strain C600. Phage 6220 shared a similar mor phology and a high degree of DNA homology with Stx(2)-encoding phage 933W, which originates from EHEC O157. In contrast, few similarities were found b etween phage 6220 and Stx(1)-encoding bacteriophage H-19B from EHEC O26.