Drug response and genetic properties of Vibrio cholerae associated with endemic cholera in north-eastern Thailand, 2003–2011

Abstract

Cholera, caused by Vibrio cholerae, results in significant morbidity and mortality worldwide, including Thailand. Representative V. cholerae strains associated with endemic cholera (n532), including strains (n53) from surface water sources, in Khon Kaen, Thailand (2003-2011, were subjected to microbiological, molecular and phylogenetic analyses. According to phenotypic and related genetic data, all tested V. cholerae strains belonged to serogroup O1, biotype El Tor (ET), Inaba (IN) or Ogawa (OG). All of the strains were sensitive to gentamicin and ciprofloxacin, while multidrug-resistant (MDR) strains showing resistance to erythromycin, tetracycline, trimethoprim/ sulfamethoxazole and ampicillin were predominant in 2007. V. cholerae strains isolated before and after 2007 were non-MDR. All except six diarrhoeal strains possessed ctxA and ctxB genes and were toxigenic altered ET, confirmed by MAMA-PCR and DNA sequencing. Year-wise data revealed that V. cholerae INET strains isolated between 2003 and 2004, plus one strain isolated in 2007, lacked the RS1 sequence (rstC) and toxin-linked cryptic plasmid (TLC)-specific genetic marker, but possessed CTX CL prophage genes ctxB CL and rstR CL . A sharp genetic transition was noted, namely the majority of V. cholerae strains in 2007 and all in 2010 and 2011 were not repressor genotype rstR CL but instead were rstR ET , and all ctx + strains possessed RS1 and TLCspecific genetic markers. DNA sequencing data revealed that strains isolated since 2007 had a mutation in the tcpA gene at amino acid position 64 (NAS). Four clonal types, mostly of environmental origin, including subtypes, reflected genetic diversity, while distinct signatures were observed for clonally related, altered ET from Thailand, Vietnam and Bangladesh, confirmed by distinct subclustering patterns observed in the PFGE (NotI)-based dendrogram, suggesting that endemic cholera is caused by V. cholerae indigenous to Khon Kaen.3These authors contributed equally to this work.Abbreviations: AMP, ampicillin; CL, classical; CTX, cholera toxin; E, erythromycin; ET, El Tor; MAMA, mismatch amplification mutation assay; MDR, multidrug resistant; SXT, trimethoprim/sulfamethoxazole; TE, tetracycline; TLC, toxin-linked cryptic plasmid. INTRODUCTIONCholera is a severe form of acute diarrhoea, caused by the gamma-proteobacterium Vibrio cholerae. V. cholerae comprises more than 200 'O' serogroups even though the disease historically has been considered to be caused only by V. cholerae serogroups O1 and O139 . Serogroup O1 has two biotypes, Classical (CL) and El Tor (ET), of which the former is associated with the first six pandemics starting in 1817 before the latter was isolated at the beginning of the current ongoing seventh cholera pandemic in the 1960s (Kaper et al., 1995). The CL biotype differs from the ET biotype in some phenotypic traits, primarily haemolysis of sheep erythrocytes, agglutination of chicken erythrocytes, Voges-Proskauer reaction, sensitivity to polymyxin B and sensitivity to specific phages (Kaper e...

Characterization and Genetic Variation of Vibrio cholerae Isolated from Clinical and Environmental Sources in Thailand

“…cholerae however, the biotype V . cholerae O1 classical has not been detected since 1986 [27, 44–46]. Interestingly, this study revealed that two strains obtained from stool samples in 2000 were identified as the Classical biotype and were genetically similar to the strains related to the 6 th cholera pandemic (Table E in S1 File).…”

“…These genes have previously been used to classify V . cholerae strains [27, 30, 41–43]. The tested strains were classified into serogroups O1, O139, and non-O1/non-O139 showing that both V .…”

“…Antimicrobial treatments have been recommended for only severe dehydration cases. Nonetheless, the occurrence of resistant strains has dramatically increased [27]. The presence of the SXT element and class I integron have been reported to contribute to the spread of antimicrobial resistance genes among V .…”

Cholera Outbreaks in South and Southeast Asia: Descriptive Analysis, 2003–2012

“…The cholera toxin produced by this variety showed both epitypic and genotypic transitions that might be associated with cholera epidemics in Bangladesh (9). A distinct genetic transition was also observed with V. cholerae-associated diarrhea in Northeastern Thailand during 2007, 2010, and 2011 (89). All the isolated strains belonged to serogroup O1, biotype El Tor, serotype Inaba or Ogawa, and most strains had toxigenic altered El Tor, ctxA and ctxB genes.…”

“…However, cholera epidemics in South and Southeast Asia have shown diverse patterns in recent years. In some of these countries, the incidence of cholera has declined (e.g., in Laos since 2001) (87); in some countries, there has been a reemergence of previously identified strains (e.g., V. cholerae O139 in Bangladesh during 2002) (88), while in others (e.g., Thailand [89], Vietnam [90], and Bangladesh [91]), new strains have emerged with different phenotypic and genotypic expressions that seem to be associated with the development of multidrug resistance, disease severity, and epidemic potential.…”