Mutation Induced by Vibriophage PS 166 Infection Changes Biotype and Phage Type of Vibrio Cholerae

Bacteriophage induces profound changes in Vibrio cholerae either by lysogenisation or by selection of resistant mutants (Mukerjee, 1983). These changes may involve pathogenic traits, e.g., lysogenisation with temperate phage obtained from an epidemic strain GS9 (Mukerjee, 1983) may impart virulence to V . cholerae EW6, a non-virulent strain that carries a non-functional toxin operon (Bhattacharyya et al., 1987). Not all of the virulence factors of V. cholerae have yet been characterised (Lancet, 1986), al-though lipopolysaccharide antigens and outer- membrane proteins, which are conspicuously im-munogenic in cholera patients (Pierce, 1984), are considered important in the pathogenesis of the disease (Manning et al., 1986). Some of these antigens are routinely used in serological character- isation of V. cholerae isolates. In recent years, phage-induced changes in V. cholerae have been characterised at the serological level (Ogg et al., 1978; Shigeno, 1982; Siddiqui and Bhattacharyya, 1984). This paper describes mutants of V. cholerae strain MAK757 resistant to a newly- isolated vibrio phage PS166 and their serological characterisation