Lytic and lysogenic infection of diverse Escherichia coli and Shigella strains with a verocytotoxigenic bacteriophage

A verocytotoxigenic bacteriophage isolated from a strain of enterohemorrhag ic Escherichia coli O157, into which a kanamycin resistance gene (aph3) had been inserted to inactivate the verocytotoxin gene (vt(2)), was used to in fect Enterobacteriaceae strains. A number of Shigella and E. coli strains w ere susceptible to lysogenic infection, and a smooth E. coli isolate (O107) was also susceptible to lytic infection. The lysogenized strains included different smooth E. coli serotypes of both human and animal origin, indicat ing that this bacteriophage has a substantial capacity to disseminate veroc ytotoxin genes. A novel indirect plaque assay utilizing an E. coli recA441 mutant in which phage-infected cells can enter only the lytic cycle, enabli ng detection of all infective phage, was developed.