VIBRIO-CHOLERAE NON-O1 SEROGROUP ASSOCIATED WITH CHOLERA GRAVIS GENETICALLY AND PHYSIOLOGICALLY RESEMBLES O1 EL-TOR CHOLERA STRAINS

Until recently, only Vibrio cholerae strains of the 01 serogroup have been associated with epidemic cholera. In December 1992, an outbreak o f cholera gravis in Vellore, India, was attributed to a new serogroup of V. cholerae recently designated 0139. Serogroup 0139 cholera has si nce spread to 13 countries and has reached pandemic proportions. Serog roup 0139 cholera evades immunity to 01 cholera and is not detected by the standard 01 antigen test. Understanding the origins of 0139 chole ra and determining the relatedness of 0139 to 01 cholera are necessary to devise strategies for detecting, reporting, and controlling this n ew pandemic. In order to determine the origins of this novel cholera s erogroup, 0139 was analyzed for virulence genes, for virulence protein s and their regulation, and for its genomic background. We found that 0139 and 01 V. cholerae strains of the El Tor biotype possess highly h omologous virulence genes encoding cholera toxin and toxin coregulated pill and that the regulation of virulence protein expression likewise was indistinguishable between 0139 and 01. Pulsed-field gel electroph oresis (PFGE) revealed the restriction digest pattern of 0139 strains to be closely related to that of 01 serogroup El Tor biotype cholera s trains from the Indian subcontinent. However, PFGE shelved minor diffe rences among individual 0139 cholera isolates, suggesting that 0139 V. cholerae is evolving.