Affiliation:
1. National Institute of Cholera and Enteric Diseases, Kolkata, India
2. South Texas Center for Emerging Infectious Diseases, University of Texas at San Antonio, San Antonio, Texas
Abstract
ABSTRACT
The incidence of
Vibrio cholerae
non-O1, non-O139 strains from hospitalized patients with acute diarrhea constituted 27.4% (
n
= 54) of the total 197
V. cholerae
strains isolated from patients in Kolkata, India, in 2003. Of 197 strains, 135 were identified as O1 serotype Ogawa and 2 were identified as O139. In the same time period, six O1 background rough strains that possessed all known virulence factors were identified. Serotype analysis of the non-O1, non-O139 strains placed 42 strains into 19 serogroups, while 12 remained O nontypeable (ONT); the existing serotyping scheme involved antisera to 206 serogroups. Detection of a good number of ONT strains suggested that additional serogroups have arisen that need to be added to the current serotyping scheme. The non-O1, non-O139 strains were nontoxigenic except for an O36 strain (SC124), which regulated expression of cholera toxin as O1 classical strains did. Additionally, strain SC124 carried alleles of
tcpA
and
toxT
that were different from those of the O1 counterpart, and these were also found in five clonally related strains belonging to different serogroups. Strains carrying
tcpA
exhibited higher colonization in an animal model compared to those lacking
tcpA
. PCR-based analyses revealed remarkable variations in the distribution of other virulence factors, including
hlyA
,
rtxA
,
Vibrio
seventh pandemic island I (VSP-I), VSP-II, and type III secretion system (TTSS). Most strains contained
hlyA
(87%) and
rtxA
(81.5%) and secreted cytotoxic factors when grown in vitro. Approximately one-third of the strains (31.5%) contained the TTSS gene cluster, and most of these strains were more motile and hemolytic against rabbit erythrocytes. Partial nucleotide sequence analysis of the TTSS-containing strains revealed silent nucleotide mutations within
vcsN2
(type III secretion cytoplasmic ATPase), indicating functional conservation of the TTSS apparatus.
Publisher
American Society for Microbiology
Cited by
121 articles.
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