Background: Temperate phages of Vibrio cholerae are the major force inthe emergence of newer pathogenic clones. PS166, a temperate vibriophage, has the ability to convertpathogenic biotypes of the V. Cholerae O1 serogroup. During the conversion process, PS166 also tendsto produce a group of lysogens neither reported nor characterized so far. Characterization of those lysogensmay provide insight into the emergence of newer pathogenic clones of V. Cholerae. Material/Methods: TheV. cholerae eltor strain MAK757 was used to generate PS166 lysogens which were serotyped by using antiseraspecific to V. Cholerae O1 and O139 strains. Multiplex PCR was used to compare the status of variouspathogenic markers of those lysogens. The outer membrane proteins (OMP) of the lysogens were determinedby SDS-PAGE. Results: Temperate phage PS166 infection of V. cholerae eltor MAK757 gave rise to a newkind of lysogens termed unserotypable due to their lack of reactivity to both O1 and O139 antisera. Moreover,these lysogens displayed a new phage sensitivity profile different from both classical and parental eltorbiotypes. The genetic profiles of the CTX element and VPI region of these lysogens were found to be unaltered,together with the biotype-specific markers mshA and hlyA. Though the genetic loci of major outer membraneproteins did not change after lysogenization, the outer membrane protein profile of these lysogens showedthe absence of a 40-kDa band corresponding to the toxR-controlled porin, ompT. Conclusions: We provideevidence for the vibriophage PS166-mediated lysogenic conversion of pathogenic cholera strains.

Keywords: Bacteriophages - pathogenicity, Base Sequence, DNA, Bacterial - genetics, Genes, Bacterial, Genetic Markers, Lysogeny - genetics, Serotyping, Vibrio cholerae - virology, Vibrio cholerae O1 - virology, Vibrio cholerae non-O1 - virology