Serogroup, Virulence, and Genetic Traits of Vibrio parahaemolyticus in the Estuarine Ecosystem of Bangladesh

Abstract

Forty-two strains of Vibrio parahaemolyticus were isolated from Bay of Bengal estuaries and, with two clinical strains, analyzed for virulence, phenotypic, and molecular traits. Serological analysis indicated O8, O3, O1, and K21 to be the major O and K serogroups, respectively, and O8:K21, O1:KUT, and O3:KUT to be predominant. The K antigen(s) was untypeable, and pandemic serogroup O3:K6 was not detected. The presence of genes toxR and tlh were confirmed by PCR in all but two strains, which also lacked toxR. A total of 18 (41%) strains possessed the virulence gene encoding thermostable direct hemolysin (TDH), and one had the TDH-related hemolysin (trh) gene, but not tdh. Ten (23%) strains exhibited Kanagawa phenomenon that surrogates virulence, of which six, including the two clinical strains, possessed tdh. Of the 18 tdh-positive strains, 17 (94%), including the two clinical strains, had the seromarker O8:K21, one was O9:KUT, and the single trh-positive strain was O1:KUT. None had the group-specific or ORF8 pandemic marker gene. DNA fingerprinting employing pulsed-field gel electrophoresis (PFGE) of SfiI-digested DNA and cluster analysis showed divergence among the strains. Dendrograms constructed using PFGE (SfiI) images from a soft database, including those of pandemic and nonpandemic strains of diverse geographic origin, however, showed that local strains formed a cluster, i.e., "clonal cluster," as did pandemic strains of diverse origin. The demonstrated prevalence of tdh-positive and diarrheagenic serogroup O8:K21 strains in coastal villages of Bangladesh indicates a significant human health risk for inhabitants.

Trends in the Epidemiology of Pandemic and Non-pandemic Strains of Vibrio parahaemolyticus Isolated from Diarrheal Patients in Kolkata, India

“…In the subsequent years, several other serovars were genetically grouped with O3:K6 [27], [40]. In this study, we found that pandemic serovars such as O3:K6, O1:K25, O4:K68 and O1:KUT were clustered in one clade and several new serovars remained in the other.…”

Pre-Enrichment of Estuarine and Fresh Water Environmental Samples with Sodium Chloride Yields in Better Recovery of <i>Vibrio parahaemolyticus</i>

“…Most of the environmental samples are selectively enriched first with alkaline peptone water (APW) and then plated on standard culture media for growth [17,18]. APW is the preferred enrichment medium for vibrios including V. parahaemolyticus.…”

“…parahaemolyticus [17,18,20]. The existing APW method has also been applied to detect V. parahaemolyticus in fresh water [20].…”

Association of Pandemic Vibrio parahaemolyticus O3:K6 Present in the Coastal Environment of Northwest Mexico with Cases of Recurrent Diarrhea between 2004 and 2010

“…It has been reported that these serotypes probably originated from the same clone as O3:K6 (8,15,36). On the other hand, non-O3:K6 serovars with pandemic traits are increasingly isolated worldwide, and therefore, they may possibly have pandemic potential (2).…”