STUDIES ON THE GENESIS OF VIBRIO-CHOLERAE O139 - IDENTIFICATION OF PROBABLE PROGENITOR STRAINS

Four lines of evidence suggest that the recent outbreak strains of Vib rio cholerae 0139 could have emerged from serogroup 01 strains typifie d by isolates M01 and MO477 described in this paper, which are neither truly classical nor truly El Tor in their biotype attributes. Firstly , like ah 0139 isolates, these 01 strains, isolated in Madras during a nd before the 0139 outbreak, were resistant not only to polymyxin B bu t also to all biotype-specific choleraphages, i.e. classical phage Phi 149 and El Tor phages e4 and e5. Secondly, the restriction fragment p attern (RFP) polymorphism displayed by these strains for the cholera t oxin (ctx) gene, were identical with those produced by 0139 isolates b ut were different from those of 01 type strains, namely V. cholerae 56 9B (classical) and V. cholerae MAK757 (El Tor). Thirdly, all the 0139 isolates and the two 01 isolates carried an identical large number of copies of cholera toxin gene in their chromosomes. Finally, the outer- membrane protein profiles of strains M01 and M0477 were identical to t hose of 0139 isolates but were different from those displayed by strai ns 569B and MAK757.