Clonal analysis of non-toxigenic Vibrio cholerae O1 associated with an outbreak of cholera.

We examined the clonal relationships among eight clinical isolates of non-toxigenic (NT) V. cholerae O1 associated with a cluster of cases of cholera in Warangal, Andhra Pradesh in south India and compared their relatedness to toxigenic O1 strains of classical and E1Tor biotypes and with O139 Bengal strains of V. cholerae by pulsed-field gel electrophoresis (PFGE). Phylogentic analysis of the NotI restriction fragment length polymorphism showed that all the NT. V. cholerae O1 strains formed a tight cluster with more than 80 per cent similarity. Interestingly, the NT V. cholerae O1 cluster was more closely related to V. cholerae O139 than to classical and E1Tor biotypes of V. cholerae O1 indicating closer genetic relationships between NT V. cholerae 01 and O139 Bengal strains that were isolated during the same time-frame.

Serovar, biotype, phage type, toxigenicity & antibiotic susceptibility patterns of Vibrio cholerae isolated during two consecutive cholera seasons (1989-90) in Calcutta.

Characteristics of V. cholerae isolated from patients of acute secretory diarrhoea admitted to the Infectious Diseases Hospital, Calcutta during two consecutive cholera seasons (1989 and 1990), with special emphasis on biotyping and toxigenicity, were investigated. The isolation rates of V. cholerae during 1989 and 1990 were 78 and 85.1 per cent respectively, with Inaba serotype dominating in 1989 and Ogawa in 1990. All the V. cholerae 01 strains isolated in this study belonged to biotype Eltor with phage type 4 dominating (48.8%). Most of the strains of V. cholerae were resistant to 10 and 150 micrograms/ml of 0/129 vibriostatic agent. Similarly, majority of the V. cholerae strains were resistant to furazolidone (95.7%), cotrimoxazole (83%) and tetracycline (63.1%) and several resistance patterns were encountered. All the V. cholerae 01 strains examined produced cholera toxin (CT) in amounts ranging between greater than 70 pg/ml and greater than 2.5 ng/ml. In contrast, all but one of the non-01 strains isolated in this study did not produce CT. Further studies are required to elucidate the mechanism involved in the pathogenesis of non-01 V. cholerae mediated diarrhoea.