Transduction of enteric Escherichia coli isolates with a derivative of Shiga toxin 2-encoding bacteriophage phi 3538 isolated from Escherichia coli O157 : H7

We investigated the ability of a detoxified derivative of a Shiga toxin 2 ( Stx2)-encoding bacteriophage to infect and lysogenize enteric Escherichia c oli strains and to develop infectious progeny from such lysogenized strains . The stx(2) gene of the patient E. coli O157:H7 isolate 3538/95 was replac ed by the chloramphenicol acetyltransferase (cat) gene from plasmid pACYC18 4, Phage phi 3538(Delta stx(2)::cat) was isolated after induction of E. col i O157:H7 strain 3538/95 with mitomycin. A variety of strains of enteropath ogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), Stx-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC), and E. coli from the physiological stool microflora were infected with phi 3538 (Delta stx(2)::cat), and plaque formation and lysogenic conversion of wild-type E. coil strains were investigated. With the exception of one EIEC strain, none of the E. coil strains supported the formation of plaques whe n used as indicators for phi 3538(Delta stx(2)::cat). However, 2 of 11 EPEC , 11 of 25 STEC, 2 of 7 EAEC, 1 of 3 EIEC, and 1 of 6 E. coli isolates from the stool microflora of healthy individuals integrated the phage in their chromosomes and expressed resistance to chloramphenicol. Following inductio n with mitomycin, these lysogenic strains released infectious particles of phi 3538(Delta sfx(2)::cat) that formed plaques on a lawn of E. coli labora tory strain C600, The results of our study demonstrate that phi 3538(Delta stx(2)::cat) was able to infect and lysogenize particular enteric strains o f pathogenic and nonpathogenic E. coli and that the lysogens produced infec tious phage progeny. Stx-encoding bacteriophages are able to spread stx gen es among enteric E. coli strains.