Diversity in the arrangement of the CTX prophages in classical strains of Vibrio cholerae O1

This study reports the results of a molecular analysis of the CTX prophages in classical biotype strains of Vibrio cholerae O1 of clinical origin isol ated between 1970 and 1979 in India. All strains were sensitive to group IV classical phage and polymyxin B but resistant to group 5 Fl Tor phage. The se phenotypic traits are consistent to that exhibited by the classical biot ype. PCR studies reconfirmed their biotype assignment and showed the presen ce of intact CTX prophages and the presence of the recently described toxin linked cryptic plasmid. Restriction fragment length polymorphism of rRNA g enes and pulsed-field gel electrophoresis showed clonal diversity among the strains. The most notable observation was the finding that one strain (GP1 3) has three CTX prophages while another (GP147) has four CTX prophages. Th is is the first time heterogeneity is reported in the arrangement of the CT X prophages among classical strains of V. cholerae O1. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. A ll rights reserved.