Prevalence of cholera toxin genes (ctxA and zot) among non-O1/O139 Vibrio cholerae strains from Newport Bay, California

Abstract

The examination of 137 non-O1/O139 Vibrio cholerae isolates from Newport Bay, California, indicated the presence of diverse genotypes and a temporal succession. Unexpectedly, the cholera toxin gene (ctxA) was found in 17% of the strains, of which one-third were also positive for the zot gene. This suggests that ctxA is prevalent in the region of nonepidemicity and is likely to have an environmental origin.

FIG. 1.

Diversity of environmental V. cholerae isolates from Newport Bay watershed revealed by ERIC-PCR fingerprinting. A total of 37 representative patterns of the 104 unique fingerprints generated from 137 isolates are shown. An O1 classical toxigenic strain (ATCC 11623) and an O1 El Tor nontoxigenic strain were included as references. ctxA- and zot-positive strains were detected by PCR, and the presence of ctxA was further confirmed by internal probe hybridization.

FIG. 2.

Amplification (using primers specific for the ctxA gene) of environmental non-O1/O139 V. cholerae isolates from Newport Bay, California. A subset of representative amplicons from environmental isolates is shown. M, molecular mass ladder (in base pairs); N, negative control; P, positive control (ATCC11623). Lane 1, strain BC1299b; lane 2, BC0999b; lane 3, C20200d; lane 4, C20200f; lane 5, C10899a; lane 6, C10200a.