CHARACTERIZATION OF PHENOTYPIC, SEROLOGICAL, AND TOXIGENIC TRAITS OF VIBRIO-CHOLERAE O139 BENGAL

Biochemical and physiological traits of a collection of strains of Vib rio cholerae O139 Bengal isolated from India, Bangladesh, and Thailand showed that these strains formed a phenotypically homogeneous group w ith identical characteristics that were essentially similar to those o f the O1 serogroup. Resistance to 150 mu g of the vibriostatic agent O /129 (2,4-diamino-6,7-diisopropylpteridine) and Mukherjee's El Tor pha ge 5 and classical phage IV and the nonagglutinability of the strains with O1 antiserum were the only discernible differences between the O1 39 and O1 serogroups. Extensive serological characterization further r evealed the O139 serogroup to be distinct from the existing 138 serogr oups of V. cholerae. Antiserum raised against the O139 serogroup requi red absorption with the R reference strain CA385 and with the referenc e strain representing serogroup O22 to remove cross-reacting agglutini ns. All of the 223 representative strains of V. cholerae O139 examined hybridized with DNA probes specific for the cholera toxin (CT) gene, zonula occludens toxin gene, and El Tor hemolysin gene but not with th e probe specific for the heat-stable enterotoxin gene. The amount of C T present in stool samples of patients infected with the O139 serogrou p was higher than that found in stools of patients infected with O1 EI Tor, and this echoed findings that the amount of CT produced by O139 strains in vitro was higher than that produced by the O1 El Tor strain s. The nucleotide sequences of the genes encoding the A and B subunits of CT of the O139 serogroup were identical to the sequences reported for the CT gene of 01 El Tor. The CT gene of O139 strains could be amp lified by using primers developed for detection of the CT gene of the 01 serogroup by a PCR assay, which could also be used to detect the CT gene in stool samples of patients infected with strains of the O139 s erogroup.