Studies on Toxinogenesis in Vibrio

By qualitative and quantitative immunological assays in vitro such mutants could be separated into different classes characterized either by production of no detectable choleragen (tox), or of small quantities of extracellular choleragen, or of large quantities of cell-associated choleragen but little extracellular choleragen. Analysis of proteins in concentrated culture supernates by electrophoresis in polyacrylamide gels showed that cultures from toxstrains lacked proteins with electrophoretic mobilities corresponding with choleragen or the spontaneously formed toxoid (choleragenoid). Infant rabbits infected with the toxstrains remained asymptomatic or developed milder symptoms than rabbits infected with the tox+ parental strains. When symptoms of cholera developed after inoculation with toxmutants, detectable numbers of tox+ revertants could be isolated from the intestines of the infected animals. Two toxt strains, designated M13 and M27, caused no symptoms and showed no evidence of reversion to tox+ during single passage in infant rabbits, and mutant M13 also remained avirulent and stably toxduring six cycles of serial passage in infant rabbits. Strains M13 and M27 were also noncholeragenic in adult rabbit ileal loops. Quantitative cultures of the intestines from infected inPortions of this work were presented at the 73rd Annual Meeting of the American Society for Microbiology, Miami Beach, Fla., May 1973, and at the 9th Joint Conference on Cholera, the United States-Japan Cooperative Medical Science Program, Grand Canyon, Ariz., October 1973. Received for publication 3 September 1974 and in revised form 4 November 1974. fant rabbits demonstrated that the avirulent mutant M13 can multiply in vivo and can persist in the intestinal tract