Stability of R plasmids belonging to different incompatibility groups in Vibrio cholerae "Eltor"

Twenty two resistance plasmids belonging to fourteen incompatibility groups have been transferred by conjugation into two sensitive strains of Vibrio cholerae "Eltor". Only five plasmids were stably inherited in these strains: four of these belong to group incC, and one to group incJ. All other plasmids were lost at high frequency when the bacteria were grown in drug-free medium. These facts might explain why very few multiresistant strains of V. cholerae have been isolated so far but do not exclude the possibility that epidemics of V. cholerae carrying pecular R plasmids might be observed in the future.