Serogroup, virulence, and molecular traits of Vibrio parahaemolyticus isolated from clinical and cockle sources in northeastern Thailand.

Vibrio parahaemolyticus is responsible for seafood-borne gastroenteritis worldwide. Isolates of V. parahaemolyticus from clinical samples (n=74) and cockles (Anadara granosa) (n=74) in Thailand were analyzed by serotyping, determination of virulence and related marker genes present, response to antimicrobial agents, and genetic relatedness. Serological analysis revealed 31 different serotypes, 10 of which occurred among both clinical and cockle samples. The clinical isolates commonly included the pandemic serogroup O3:K6, while a few of the cockle isolates exhibited likely pandemic serovariants such as O3:KUT and O4:KUT, but not O3:K6. The pandemic (orf8 gene-positive) strains were more frequently found among clinical isolates (78.4%) than cockle isolates (28.4%) (p<0.001). Likewise, the virulence and related marker genes were more commonly detected among clinical than cockle isolates; i.e., tdh gene (93.2% versus 29.7%), vcrD2 (97.3% versus 23.0%), vopB2 (89.2% versus 13.5%), vopT (98.6% versus 36.5%) (all p<0.001) and trh (10.8% versus 1.4%) (p<0.05). Pulsed-field gel electrophoresis of NotI-digested genomic DNA of 41 randomly selected V. parahaemolyticus isolates representing different serotypes produced 33 pulsotypes that formed 5 different clusters (clonal complexes) (A-E) in a dendrogram. Vibrio parahaemolyticus O3:K6 and likely related pandemic serotypes were especially common among the numerous clinical isolates in cluster C, suggesting a close clonal link among many of these isolates. Most clinical and cockle isolates were resistant to ampicillin. This study indicates that O3:K6 and its likely serovariants based on the PFGE clusters, are causative agents. Seafoods such as cockles potentially serve as a source of virulent V. parahaemolyticus, but further work is required to identify possible additional sources.

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

Cholera, caused by Vibrio cholerae, results in significant morbidity and mortality worldwide, including Thailand. Representative V. cholerae strains associated with endemic cholera (n = 32), including strains (n = 3) 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 TLC-specific genetic markers. DNA sequencing data revealed that strains isolated since 2007 had a mutation in the tcpA gene at amino acid position 64 (N→S). 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.

Molecular analysis and antimicrobial resistance of Vibrio cholerae O1 in northeastern Thailand.

A total of 84 clinical Vibrio cholerae O1 isolates were collected from Khon Kaen (KK), Udon Thani (UT), Loei (LI), and Nong Khai (NK), northeastern Thailand during cholera outbreaks in 2007 and 2008. The majority of V. cholerae O1 strains carried nearly all the virulence-associated genes (ctxA, zot, and ace) except for four isolates and one isolate from UT and NK, respectively, which carried only tcpA, ompU, hlyA and toxR. None of the V. cholerae O1 strains carried sto. Pulsed field gel-electrophoresis (PFGE) profiling of 16 randomly chosen isolates showed the same PFGE pattern, except for one NK isolate, which was sensitive to all seven antibiotics used in the antimicrobial susceptibility tests. The tests revealed that multi-drug resistance to tetracycline and co-trimoxazole were present in KK strains (92%), followed by LI (75%) and UT (52%) strains. All strains were sensitive to norfloxacin but intermediate resistance to ciprofloxacin was found in a single strain from KK and LI. Differences in antimicrobial resistance among V. cholerae strains with the same PFGE pattern reflect differences in the antimicrobial agents used in each area of northeastern Thailand.

Antimicrobial resistance surveillance of Vibrio cholerae in Thailand from 2000 to 2004.

OBJECTIVE: To study the trends of antimicrobial resistance pattern of Vibrio cholerae in Thailand between 2000 and 2004. MATERIAL AND METHOD: All isolates of Vibrio cholerae from 28 hospitals across Thailand between 2000 and 2004 were tested for their susceptibility to ampicillin, chloramphenicol, norfloxacin, tetracycline and trimethoprim/sulfamethoxazole by the disk diffusion method (Kirby Bauer). The relevant data were collected and analyzed by the WHONET software program supported by the World Health Organization (WHO). RESULTS: V. cholerae O1, serotype Inaba was much more common than serotype Ogawa. The most frequent type of clinical specimens that V. cholerae isolated was the stool. There was no trend of increasing resistance of all V. cholerae both O1 and non O1. Over all average rates of tetracycline resistance of V. cholerae O1, Inaba and Ogawa were 0.9% and 16.3% respectively and trimethoprim/sulfamethoxazole resistance were 0.4% and 60.5% respectively. The strains were not resistant to norfloxacin. CONCLUSION: In Thailand, V. cholerae O1 were still susceptible to tetracycline and norfloxacin which were the most frequently antimicrobial used for the treatment of cholera. The trend of increasing resistance during the study period was not detected.