Genomic organisation of the CTX element among toxigenic Vibrio cholerae isolates

Abstract

The composition and gene arrangement of the CTX genetic element were compared in 36 Vibrio cholerae isolates obtained during 2004-2006 from Iran. Long-PCR amplification of the CTX genetic element, using primers targeting ig1 and attB2, revealed three PCR products of c. 6.9, 5.6 and 2.6 kb, respectively. Southern blot hybridisation revealed that 30%, 17% and 53% of the isolates had one, two and three copies of the zot gene, respectively. PCR analysis of internal regions showed that isolates with three copies of the CTX genetic element carried one complete (6.9 kb) and two truncated CTX elements (each of 5.6 kb). In contrast, isolates with one or two copies of CTX carried the complete 6.9-kb CTX element. Pulsed-field gel electrophoresis revealed two pulsotypes among the isolates, with 75% of the isolates belonging to pulsotype 2. The pulsotype 2 isolates had varying CTX genomic arrangements, whereas the pulsotype 1 isolates had a homogeneous CTX arrangement. Thus, variations in the content, arrangement and copy number of the CTX genetic element may occur in isolates belonging to the same clone.

Characterization of pathogenicity island prophage in clinical and environmental strains of Vibrio cholerae

“…Vibrio cholerae O1 causes acute gastrointestinal disease, which is reported annually in Iran with differing frequency (Bakhshi et al, 2008). However, non-O1/non-O139 strains are not associated with epidemics, but several cases of sporadic diarrhoea, gastroenteritis and skin infections have been reported (Restrepo et al, 2006;Rozemeijer et al, 2009).…”

Quantitative expression of cholera toxin mRNA in Vibrio cholerae isolates with different CTX cassette arrangements

“…In total, 94 clinical isolates of V. cholerae O1 El Tor obtained from different outbreaks between 2004 and 2009 were studied. A previous study in this laboratory showed that these isolates were Inaba and Ogawa serotypes (Bakhshi et al, 2008). In the present study, three strains were selected randomly, one from each of the three different arrangements of the CTX cassette.…”

“…The RS2 element is like RS1 but lacks the rstC ORF; thus, the CTX cassette contains only the rstA, rstB and rstR ORFs (Davis & Waldor, 2003). A previous report by this laboratory showed that, among V. cholerae isolates obtained from various parts of Iran, three distinct CTX cassettes with different arrangements existed (Bakhshi et al, 2008) (Fig. 1).…”

“…Today, we are facing the continuation of the seventh cholera pandemic, which has been spread from South-east Asia across the Middle East into Central America and Africa (Pourshafie et al, 2000). Cholera toxin (CT) is a potent enterotoxin that plays a major role in the pathogenesis of Vibrio cholerae through a complex cooperation with CTXW phage and other phages (Bakhshi et al, 2008). Environmental factors also affect expression of CT through a number of regulatory genes such as tcpP, tcpH and toxT.…”

Evaluation of Cholera Toxin Expression in Different Populations of Vibrio cholera

“…Vibrio cholerae is the causative agent of cholera; which can cause a considerable difficulties like diarrhea, dehydrates the body, acidosis, shock and ultimately death (2). The burden of this disease is well documented in the world and so far, seven global pandemic of cholera is reported (3,4). As many scientists from all over the world believe that many pathogenic bacteria have the quorum sensing system which is one of the major virulence factors (5).…”