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Characterization of a Vibrio alginolyticus strain, isolated from Alaskan oysters, carrying a hemolysin gene similar to the thermostable direct hemolysin-related hemolysin gene (trh) of Vibrio parahaemolyticus.

ABSTRACT: A Vibrio strain isolated from Alaskan oysters and classified by its biochemical characteristics as Vibrio alginolyticus possessed a thermostable direct hemolysin-related hemolysin (trh) gene previously reported only in Vibrio parahaemolyticus. This trh-like gene was cloned and sequenced and was 98% identical to the trh2 gene of V. parahaemolyticus. This gene seems to be functional since it was transcriptionally active in early-stationary-phase growing cells. To our knowledge, this is the first report of V. alginolyticus possessing a trh gene.

SUBMITTER: Gonzalez-Escalona N

PROVIDER: S-EPMC1694234 | biostudies-literature | 2006 Dec

REPOSITORIES: biostudies-literature

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Characterization of a Vibrio alginolyticus strain, isolated from Alaskan oysters, carrying a hemolysin gene similar to the thermostable direct hemolysin-related hemolysin gene (trh) of Vibrio parahaemolyticus.

González-Escalona Narjol N Blackstone George M GM DePaola Angelo A

Applied and environmental microbiology 20061020 12

A Vibrio strain isolated from Alaskan oysters and classified by its biochemical characteristics as Vibrio alginolyticus possessed a thermostable direct hemolysin-related hemolysin (trh) gene previously reported only in Vibrio parahaemolyticus. This trh-like gene was cloned and sequenced and was 98% identical to the trh2 gene of V. parahaemolyticus. This gene seems to be functional since it was transcriptionally active in early-stationary-phase growing cells. To our knowledge, this is the first r ...[more]

PMID: 17056701

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Project description:In an effort to identify the regulatory gene controlling the expression of the tdh gene, encoding the thermostable direct hemolysin of Vibrio parahaemolyticus, we examined total DNA of AQ3815 (a Kanagawa phenomenon-positive strain) for sequences homologous to that of the toxR gene of Vibrio cholerae. The extracted DNA gave a weak hybridization signal under reduced-stringency conditions with a toxR-specific DNA probe. Cloning and sequence analysis of the probe-positive sequence revealed an operon (Vp-toxRS) which was highly similar to the toxRS operon of V. cholerae (Vc-toxRS) (52 and 62% similarities in the two genes, respectively). The deduced amino acid sequences of the Vp-toxRS gene products (Vp-ToxRS) contained regions similar to the proposed transmembrane and activity domains of the Vc-toxRS gene products (Vc-ToxRS). All clinical and environmental strains of V. parahaemolyticus examined possessed the Vp-toxRS genes. In the presence of Vp-ToxS, Vp-ToxR promoted expression of the tdh2 gene, one of two tdh genes (tdh1 and tdh2) carried by Kanagawa phenomenon-positive strains. The DNA sequence located 144 bp upstream of the tdh2 coding region was shown to be important for the Vp-ToxR-stimulated expression of the tdh2 gene in an Escherichia coli background. Comparative analysis of AQ3815 and its isogenic Vp-toxR null mutant gave the following results: (i) Vp-ToxR promoted, in an AQ3815 background, expression of the tdh gene to different degrees in various culture media, with KP broth (2% peptone, 0.5% NaCl, 0.03 M KH2PO4, pH 6.2) being most effective (12-fold); (ii) the promotion of tdh gene expression in KP broth was at the level of transcription; and (iii) Vp-ToxR was essential for demonstration of enterotoxic activity of AQ3815 in the rabbit ileal loop, a model previously used to demonstrate thermostable direct hemolysin-mediated enterotoxic activity of AQ3815. These results demonstrate that Vp-ToxR and Vc-ToxR share a strikingly similar function, i.e., direct stimulation at the transcriptional level of the gene encoding a major virulence determinant (enterotoxin) of a Vibrio species.

Project description:Vibrio parahaemolyticus and Vibrio vulnificus are naturally occurring estuarine bacteria and are the leading causes of seafood-associated infections and mortality in the United States. Though multiple-antibiotic-resistant V. parahaemolyticus and V. vulnificus strains have been reported, resistance patterns in vibrios are not as well documented as those of other foodborne bacterial pathogens. Salinity relaying (SR) is a postharvest processing (PHP) treatment to reduce the abundances of these pathogens in shellfish harvested during the warmer months. The purpose of this study was to evaluate the antimicrobial susceptibility (AMS), pathogenicity, and genetic profiles of V. parahaemolyticus and V. vulnificus recovered from oysters during an oyster relay study. Isolates (V. parahaemolyticus [n = 296] and V. vulnificus [n = 94]) were recovered from oysters before and during the 21-day relaying study to detect virulence genes (tdh and trh) and genes correlated with virulence (vcgC) using multiplex quantitative PCR (qPCR). AMS to 20 different antibiotics was investigated using microbroth dilution, and pulsed-field gel electrophoresis (PFGE) was used to study the genetic profiles of the isolates. Twenty percent of V. vulnificus isolates were vcgC+, while 1 and 2% of V. parahaemolyticus were tdh+ and trh+, respectively. More than 77% of the V. vulnificus isolates and 30% of the V. parahaemolyticus isolates were resistant to at least one antimicrobial. Forty-eight percent of V. vulnificus and 8% of V. parahaemolyticus isolates were resistant to two or more antimicrobials. All isolates demonstrated a high genetic diversity, even among those isolated from the same site and having a similar AMS profile. No significant effects of the relaying process on AMS, virulence genes, or PFGE profiles of V. vulnificus and V. parahaemolyticus were observed.IMPORTANCE Analysis of the antibiotic resistance profiles of V. vulnificus and V. parahaemolyticus isolated from oysters during this study indicated that more than 48% of V. vulnificus isolates were resistant to two or more antimicrobials, including those recommended by the CDC for treating Vibrio infections. Also, the V. parahaemolyticus isolates showed high MICs for some of the Vibrio infection treatment antibiotics. Monitoring of AMS profiles of this bacterium is important to ensure optimal treatment of infections and improve food safety. Our study showed no significant differences in the AMS profiles of V. vulnificus (P = 0.26) and V. parahaemolyticus (P = 0.23) isolated from the oysters collected before versus after relaying. This suggests that the salinity of the relaying sites did not affect the AMS profiles of the Vibrio isolates, although it did reduce the numbers of these bacteria in oysters (S. Parveen et al., J Food Sci 82:484-491, 2017, https://doi.org/10.1111/1750-3841.13584).

Project description:We have demonstrated that possession of the gene for thermostable direct hemolysin-related hemolysin (trh) coincides with the presence of the urease gene among clinical Vibrio parahaemolyticus strains and that the location of the two genes are in close proximity on the chromosome. Here, we cloned and sequenced the 15,754-bp DNA region containing the trh gene and the gene cluster for urease production from the chromosome of clinical V. parahaemolyticus (TH3996). We found 16 open reading frames (ORFs) and a lower G+C content (41%) compared with the total genome of this bacterium (46 to 47%). The ure cluster consisted of eight genes, namely, ureDABCEFG and ureR. ureR was located 5.2 kb upstream of the other seven genes in the opposite direction. The genetic organization and sequences of the ure genes resembled those found in Proteus mirabilis. Between ureR and the other ure genes, there were five ORFs, which are homologous with the nickel transport operon (nik) of Escherichia coli. We disrupted each of the ureR, ureC, and nikD genes in TH3996 by homologous recombination and analyzed the phenotype of the mutants. In the presence of urea these mutant strains had dramatically less urease activity than the strain they were derived from. Disruption of ureR, nikD, or ureC, however, had no effect on TRH production. The DNA region containing the trh, nik, and ure genes was found in only trh-positive strains and not in Kanagawa phenomenon-positive and environmental V. parahaemolyticus strains. At the end of the region, an insertion sequence-like element existed. These results suggest that the DNA region was introduced into V. parahaemolyticus in the past through a mechanism mediated by insertion sequences. This is the first reported case that the genes for an ATP-binding cassette-type nickel transport system, which may play a role in nickel transport through bacterial cytoplasmic membrane, are located adjacent to the ure cluster on the genome of an organism.

Dataset Information

Characterization of a Vibrio alginolyticus strain, isolated from Alaskan oysters, carrying a hemolysin gene similar to the thermostable direct hemolysin-related hemolysin gene (trh) of Vibrio parahaemolyticus.

Publications

Characterization of a Vibrio alginolyticus strain, isolated from Alaskan oysters, carrying a hemolysin gene similar to the thermostable direct hemolysin-related hemolysin gene (trh) of Vibrio parahaemolyticus.

Similar Datasets

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