Survival of toxigenic Vibrio cholerae O1 with a common duckweed, Lemna minor, in artificial aquatic ecosystems

Abstract
Cholera epidemics occur twice a year in Bangladesh. During epidemics, Vibrio cholerae O1 are isolated from patients, as well as from the surface water, but the bacteria disappear during inter-epidemic periods. Their reservoirs or sites of survival and multiplication during inter-epidemic period are still unknown. The present survival study in the laboratory explored the role of an aquatic plant, Lemna minor (duckweed), as a possible reservoir. L. minor was added to sea-salt solution at pH 8·5, containing V. cholerae. Survival of V. cholerae on L. minor, in water on which L. minor was floating, and in control water (without L. minor) was monitored at regular intervals. Survival of both environmental and clinical strains of V. cholerae was assessed by viable counts on thiosulphate-citrate-bile salt-sucrose agar. It was observed that both strains survived better on L. minor than in water on which L. minor was floating or in control water. It is suggested that plants may serve as an effective environmental reservoir for V. cholerae either through a non-specific association or by interaction with V. cholerae in commensal relationship.