Clinical and environmental isolates of Vibrio cholerae serogroup O141 carry the CTX phage and the genes encoding the toxin-coregulated pili

We report sporadic cases of a severe gastroenteritis associated with Vibrio cholerae serogroup O141. Like O1 and O139 serogroup strains of V. cholerae isolated from cholera cases, the O141 clinical isolates carry DNA sequence s that hybridize to cholera toxin (CT) gene probes. The CT genes of OI and O139 strains are carried by a filamentous bacteriophage (termed CTX phage) which is known to use toxin-coregulated pili (TCP) as its receptor. In an e ffort to understand the mechanism of emergence of toxigenic O141 V. cholera e, we probed a collection of O141 clinical and environmental isolates for g enes involved in TCP production, toxigenicity, virulence regulation, and ot her phylogenetic markers. The collection included strains isolated between 1964 and 1995 from diverse geographical locations, including eight countrie s and five U.S. states. Information collected about the clinical and enviro nmental sources of these isolates suggests that they had no epidemiological association. All clinical O141 isolates hybridized to probes specific for genes encoding CT (ax), zonula occludens toxin (zot), repetitive sequence 1 (RS1), RTX toxin (rtxA), the major subunit of TCP (tcpA), and the essentia l regulatory gene that controls expression of both CT and TCP (toxR). In co ntrast, all but one of the nonclinical O141 isolates were negative for ctx, zot, RS1, and tcpA, although these strains were positive for rtxA and toxR . The one toxigenic environmental O141 isolate was also positive for tcpA. Ribotyping and CT typing showed that the O141 clinical isolates were indist inguishable or closely related, while a toxigenic water isolate from Louisi ana showed a distantly related ribotype. Nonclinical O141 isolates displaye d a variety of unrelated ribotypes. These data support a model for emergenc e of toxigenic O141 that involves acquisition of the CTX phage sometime aft er these strains had acquired the pathogenicity island encoding TCP. The cl onal nature of toxigenic O141 strains isolated from diverse geographical lo cations suggests that the emergence is a rare event but that once it occurs , toxigenic O141 strains are capable of regional and perhaps even global di ssemination. This study stresses the importance of monitoring V. cholerae n on-O1, non-O139 serogroup strains for their virulence gene content as a mea ns of assessing their epidemic potential.