Gastroenteritis due to Kanagawa negative Vibrio parahaemolyticus

Sequence of a cloned pR72H fragment and its use for detection of Vibrio parahaemolyticus in shellfish with the PCR

The nucleotide sequence of pR72H cloned from Vibrio parahaemolyticus 93 was determined. We examined all V. parahaemolyticus gene sequences published in the GenBank-EMBL databases for homology and found that no other DNA sequence of V. parahaemolyticus was highly homologous to the sequence reported in this study. A pair of primers, VP33-VP32, derived from a pR72H fragment were selected to detect V. parahaemolyticus. The sensitivity of PCR detection for a pure culture of V. parahaemolyticus was 10 cells from crude bacterial lysates. Furthermore, a detection level of 2.6 fg, equivalent to 1 cell, was obtained by using purified chromosomal DNA as the template. The expected PCR products were obtained from all V. parahaemolyticus strains tested (n = 124), while no PCR amplicons were found in other vibrios or related genera (n = 50). High levels (10(6) to 10(10) CFU/ml) of Escherichia coli cells did not affect the PCR assay sensitivity. The presence of 10(8) V. parahaemolyticus cells or 10(9) E. coli cells in the PCR mixtures completely inhibited the PCR. When oyster samples were inoculated with V. parahaemolyticus 93 and cultured in tryptic soy broth containing 3% NaCl for 3 h at 35 degrees C, an initial sample inoculum level of 9.3 CFU/g was detected in a PCR assay with crude bacterial lysates. The PCR assay with enrichment culturing in salt polymyxin broth was compared with the conventional method for naturally contaminated shellfish and fish samples. We conclude that this PCR assay with enrichment culturing is a good alternative method for the detection of V. parahaemolyticus.

Evaluation of two assay kits for thermostable direct hemolysin (TDH) as an indicator of TDH-related hemolysin (TRH) produced by Vibrio parahaemolyticus

Reversed passive latex agglutination (RPLA) or enzyme-linked immunosorbent assay kits with beads (Bead-ELISA) are commercially available in Japan to detect the thermostable direct hemolysin (TDH) produced by Vibrio parahaemolyticus isolates. We evaluated whether these kits can be used to assay the pathogenic toxin, TDH-related hemolysin (TRH), produced by some so-called Kanagawa phenomenon-negative V. parahaemolyticus strains isolated from patients with diarrhea. Our results showed that the two kits, RPLA and Bead-ELISA, can detect TRH, although they were originally developed for detection of TDH. This may be due to the use of polyclonal anti-TDH antisera that cross react with TRH. Although the sensitivity for TDH detection by RPLA and Bead-ELISA differed tenfold, that for TRH detection was essentially equal. The minimum concentration of TRH required for detection by the two assay kits was about 10 ng/ml.

Ocorrência de Vibrio parahaemolyticus em mexilhões (Perna perna, Linnaeus, 1758) de banco natural do litoral do município de Palhoça, Santa Catarina, Brasil

Foi estudada a ocorrência de Vibrio parahaemolyticus em quarenta amostras de mexilhões (Perna perna, Linnaeus, 1758) procedentes de banco natural da praia da Pinheira, município de Palhoça, Santa catarina, durante um período de três meses. Na metodologia de isolamento foi utilizada a técnica do Número Mais Provável (NMP) com enriquecimento em água alcalina peptonada e subseqüente plaqueamento em ágar TCBS (thiosulfate citrate bile salts sucrose). Em 52,5% das amostras de mexilhões foi constatada a presença de Vibrio parahaemolyticus, com níveis de contaminação entre <3 e 93 NMP/g. Na caracterização sorológica de 61 culturas, 36,1% não permitiram a identificação das estruturas antigênicas O e K; 54,1% somente da estrutura K e apenas 8,2% tiveram ambas as estruturas definidas. Nenhuma dessas culturas apresentou positividade para o teste de Kanagawa.

Effects of iron limitation on production of a siderophore, outer membrane proteins, and hemolysin and on hydrophobicity, cell adherence, and lethality for mice of Vibrio parahaemolyticus

Vibrio parahaemolyticus is one of the most important enteropathogens in Taiwan, Japan, and other coastal regions. The pathogenesis of V. parahaemolyticus disease is not clearly understood. The expression of some factors by V. parahaemolyticus in iron-rich and iron-limited media was analyzed. In the clinical hemolytic strains, the production of a siderophore, two outer membrane proteins (77 and 80 kDa), and thermostable direct hemolysin was significantly enhanced in iron-limited culture, and hemolytic activities, cell hydrophobicity, HEp-2 cell adherence, and lethality for mice were also enhanced. The environmental nonhemolytic strain CCRC12958 that was cultured in iron-limited medium exhibited lethal activity for mice, and other factors except hemolysis were also enhanced like the responses of clinical strains were. These results suggested that a virulent factor(s) of V. parahaemolyticus may be induced or enhanced under iron-limited conditions. The iron-regulated factors reported in this paper may be important in the pathogenesis of V. parahaemolyticus disease.

Analysis of the tdh gene cloned from a tdh gene- and trh gene-positive strain of Vibrio parahaemolyticus

A variant of the gene (tdh) encoding thermostable direct hemolysin (TDH) was cloned from the chromosome of Vibrio parahaemolyticus AQ3860, which gave positive results in the hybridization tests with the tdh gene probe and the trh (tdh-related hemolysin) gene probe and showed a low level of reaction in an enzyme-linked immunosorbent assay for TDH. Nucleotide sequence analysis of the cloned gene (tdh5) provided no evidence that tdh5 is evolutionally closer to the trh gene than the other tdh genes. The tdh5 gene was flanked by 40 base-pair sequences constituting perfect inverted repeats, which may suggest association of the tdh5 gene with insertion sequence-like structure. These results suggest that the tdh5 gene and the trh gene were not originally produced by gene duplication in AQ3860 but rather that one of the two genes moved into AQ3860 from an external source.

Characterization of a new thermostable direct haemolysin produced by a Kanagawa-phenomenon-negative clinical isolate of Vibrio parahaemolyticus

The production of two haemolysins, thermostable direct haemolysin (Vp-TDH) and a Vp-TDH-related haemolysin (Vp-TRH), by clinical isolates of Vibrio parahaemolyticus has previously been reported. Here we describe a third type of haemolysin (named Vp-TDH/I), which is produced by a clinical isolate (strain TH012) that is Kanagawa phenomenon negative. Vp-TDH/I was purified by a series of column chromatographies on DEAE-Sephadex A25, hydroxyapatite, Sepharose 4B and Mono Q. By physicochemical, biological and immunological analyses, Vp-TDH/I was demonstrated to be similar, but not identical, to Vp-TDH and Vp-TRH. The gene encoding Vp-TDH/I was cloned and the deduced amino acid sequence of Vp-TDH/I confirmed that Vp-TDH/I has a sequence different from those of previously known Vp-TDH and Vp-TRH. Not only purified Vp-TDH/I but also live cells of the Vp-TDH/I-producing strain induced fluid accumulation in ligated rabbit intestine. We conclude that this clinical isolate produces a new type of Vp-TDH-related haemolysin, which may be involved in the pathogenesis of this organism.

Molecular epidemiologic evidence for association of thermostable direct hemolysin (TDH) and TDH-related hemolysin of Vibrio parahaemolyticus with gastroenteritis

The Kanagawa phenomenon induced by the thermostable direct hemolysin (TDH) of Vibrio parahaemolyticus is almost exclusively associated with clinical strains, and TDH has been considered an important virulence factor. However, Kanagawa phenomenon-negative strains isolated from patients with diarrhea have recently been shown to produce TDH-related hemolysin (TRH). We studied the distribution of the tdh gene encoding TDH and the trh gene encoding TRH in vibrios by hybridization analyses. The presence or absence of the tdh gene and the trh gene in 285 strains of V. parahaemolyticus was examined by the DNA colony hybridization test with a tdh gene-specific probe and a newly constructed trh gene-specific probe. For assessment of the importance of TRH, many Kanagawa phenomenon-negative clinical strains (35.4% of all strains) were included. Of 214 clinical strains of V. parahaemolyticus, 112 strains (52.3%) had the tdh gene only, 52 strains (24.3%) had the trh gene only, and 24 strains (11.2%) carried both the tdh and the trh gene. The coexistence of the tdh and trh genes in these 24 strains was confirmed by Southern blot hybridization analysis. Of 71 environmental strains, 5 strains (7.0%) hybridized very weakly with the trh gene probe and none hybridized with the tdh gene probe. These results suggest that TRH as well as TDH is an important virulence factor of V. parahaemolyticus. Among 118 strains of other Vibrio species examined for the trh gene, only 1 strain of Vibrio furnissii gave a very weak hybridization signal. Among 48 representative trh gene-positive strains of V. parahaemolyticus, only 18 strains (37.5%) were found to produce TRH in culture medium when examined by a sensitive enzyme-linked immunosorbent assay method.

Production of monoclonal antibody against a hemolysin (Vp-TRH) produced by Vibrio parahaemolyticus

The antigenicity of a hemolysin (Vp-TRH: Vp-TDH related hemolysin) produced by Kanagawa phenomenon-negative clinical isolates of Vibrio parahaemolyticus was studied using monoclonal antibodies (MAbs). A total of 12 hybridoma clones which produced MAbs against Vp-TRH were established. All MAbs contained the Kappa light chain and were IgG type. These MAbs were divided into a minimum of 5 different specificity groups, including antibodies specific to Vp-TRH and common to both Vp-TRH and Vp-TDH, a possible pathogenic toxin of Kanagawa phenomenon-positive V. parahaemolyticus. These results clearly show the immunological similarity and dissimilarity (specificity) of Vp-TRH and Vp-TDH.

Urease-positive, Kanagawa-negative Vibrio parahaemolyticus from patients and the environment in the Pacific Northwest

We previously reported the occurrence of Vibrio parahaemolyticus in patients and the environment in the Pacific Northwest. The present studies compare the biochemical characteristics, Kanagawa hemolysin reactions, and plasmid profiles of 13 patient and 221 environmental isolates of the organism. Classical biochemical testing of the isolates revealed similar reactions for the clinical and environmental strains, and analysis in agarose gels revealed that 13 to 15% of the isolates had plasmids. The strains were tested for production of Kanagawa hemolysin on Wagatsuma agar, and 1.4% of environmental isolates and 23% of clinical isolates were positive. Clinical isolates from locally acquired extraintestinal infections were urease negative and Kanagawa hemolysin negative, isolates from locally acquired gastroenteritis cases were urease positive and Kanagawa negative, and isolates from traveler's diarrhea were urease negative and Kanagawa positive. Eight percent of the local environmental isolates were also urease positive and Kanagawa hemolysin negative. These findings suggest that expression of the Kanagawa hemolysin is not essential for the pathogenesis of V. parahaemolyticus infections. In addition, our findings suggest that V. parahaemolyticus gastroenteritis in the Pacific Northwest is associated with a urease-positive, Kanagawa-negative biotype of the organism.

Cloning and nucleotide sequence of the gene (trh) encoding the hemolysin related to the thermostable direct hemolysin of Vibrio parahaemolyticus

Vibrio parahaemolyticus isolates derived from an outbreak of gastroenteritis in the Republic of Maldives did not have the genetic potential to produce the thermostable direct hemolysin, but one such isolate produced a hemolysin immunologically related to the thermostable direct hemolysin (T. Honda, Y. Ni, and T. Miwatani, Infect. Immun. 56:61-965, 1988). The Maldives isolates hybridized with the DNA probe for the gene encoding the thermostable direct hemolysin (the tdh gene) under reduced stringencies. A DNA fragment containing the probe-reactive nucleotide sequence was isolated from a selected strain and cloned into pBR322 in Escherichia coli. A clone producing the thermostable direct hemolysin-related hemolysin was obtained by screening with hemolysis assays and by an immunological assay. Nucleotide sequence analysis of the cloned DNA fragment revealed that the gene encoding the thermostable direct hemolysin-related hemolysin (the trh gene), like the tdh gene, encoded the hemolysin subunit composed of 189 amino acid residues. The trh gene had significant nucleotide sequence homology with the tdh gene (68.4% with the tdh1 gene copy and 68.6% with the tdh2 gene copy). The amino acid sequences of the hemolysin subunits deduced from the nucleotide sequences of the trh gene and tdh gene were homologous (61.9% homology with the tdh1-encoded subunit and 63.0% homology with the tdh2-encoded subunit) and contained the two cysteine residues to form an intrachain bond at the same positions, and their possible conformations appeared to be similar as determined by hydrophobicity-hydrophilicity analysis and a secondary structure prediction. The trh and tdh genes may have had a common ancestor and may have evolved by single-base changes so that they maintained the fundamental architecture of the molecules.

Occurrence and distribution of Vibrio spp., Listonella spp., and Clostridium botulinum in the Seto Inland Sea of Japan

The distribution of Vibrio species in samples of surface water, bottom water (water 2 m above the sediment), and sediment from the Seto Inland Sea was studied. A simple technique using a membrane filter and short preenrichment in alkaline peptone water was developed to resuscitate the injured cells, followed by plating them onto TCBS agar. In addition, a survey was conducted to determine the incidence of Clostridium botulinum in sediment samples. Large populations of heterotrophs were found in surface water, whereas large numbers of total vibrios were found in bottom water. In samples from various water sampling regions, high counts of all bacterial populations were found in the inner regions having little exchange of seawater when compared with those of the open region of the inland sea. In the identification of 463 isolates, 23 Vibrio spp. and 2 Listonella spp. were observed. V. harveyi was prevalent among the members of the Vibrio genus. Vibrio species were categorized into six groups; an estimated 20% of these species were in the so-called "pathogenic to humans" group. In addition, a significant proportion of this group was hemolytic and found in the Bisan Seto region. V. vulnificus, V. fluvialis, and V. cholerae non-O1 predominated in the constricted area of the inland sea, which is eutrophic as a result of riverine influence. It was concluded that salinity indirectly governs the distribution of total vibrios and analysis of variance revealed that all bacterial populations were distributed homogeneously and the variance values were found to be significant in some water sampling regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification of a TDH-related hemolysin produced by a Kanagawa phenomenon-negative clinical isolate of Vibrio parahaemolyticus 06: K46

A hemolysin produced by a clinical isolate of Kanagawa phenomenon-negative Vibrio parahaemolyticus 06: K46 was purified by 55% ammonium sulfate fractionation and successive column chromatographies on DEAE-cellulose, hydroxyapatite, Sepharose 4B and Mono Q. The purified hemolysin was physicochemically and immunologically identical with the Vp-TRH (V. parahaemolyticus thermostable direct hemolysin related hemolysin) recently described in V. parahaemolyticus 03: K6 (Honda et al. Infect. Immun. 56: 961-965, 1988). This indicates that V. parahaemolyticus of Kanagawa-negative clinical isolates possessing not only 03: K6 but also different serotypes such as 06: K46 produce Vp-TRH. Production of Vp-TRH by most clinical isolates of Kanagawa-negative V. parahaemolyticus was also demonstrated. These results suggest the importance of Vp-TRH among clinical isolates of Kanagawa-negative V. parahaemolyticus.

Contemporary issues: diseases with a food vector

Foodborne disease has become a contemporary issue. Several large, well-publicized outbreaks of foodborne disease have heightened public awareness that harmful microorganisms may be present in food and that chronic as well as acute disease may be caused by foodborne microbes. The field of food microbiology has likewise experienced a resurgence of interest. New tools, such as recombinant deoxyribonucleic acid technology and monoclonal antibody production, used to elucidate microbial virulence factors have facilitated identification of disease-causing microbes once thought to be harmless and demonstrated the complexity of individual virulence mechanisms previously considered to be well understood. Foodborne pathogens are also causing disease via some surprising food vectors, such as chopped, bottled garlic and sauteed onions. In addition to acute gastrointestinal disturbances, certain microorganisms may, through complex interactions with the human immune response, cause chronic diseases that affect several major organ systems. These microbes are serving as models in studies of molecular mimicry and genetic interrelatedness of procaryotes and eucaryotes. Other recently recognized attributes of foodborne microorganisms, such as the heat shock phenomenon and the possible nonculturability of some bacteria, may affect their ability to cause disease in humans. Because foodborne disease is a major cause of morbidity and mortality, the study of these diseases and their causative microorganisms presents a unique challenge to many professionals in the subdisciplines of microbiology, epidemiology, and clinical medicine.

Purification and characterization of a hemolysin produced by a clinical isolate of Kanagawa phenomenon-negative Vibrio parahaemolyticus and related to the thermostable direct hemolysin

A clinical isolate (strain 4037) of Kanagawa phenomenon-negative Vibrio parahaemolyticus was studied. Although the strain was judged to be Kanagawa phenomenon-negative by various conventional tests, it produced a new hemolysin (named Vp-TRH, for thermostable direct hemolysin [Vp-TDH]-related hemolysin) that was related to the Vp-TDH produced by ordinary Kanagawa phenomenon-positive V. parahaemolyticus. Vp-TRH was purified by ammonium sulfate fractionation and successive column chromatographies on DEAE-cellulose, hydroxyapatite, and Mono Q. The molecular weight of Vp-TRH was estimated as 48,000 by Sephadex G-100 gel filtration, and the molecular weight of the subunit was estimated to be 23,000 by sodium dodecyl sulfate-slab gel electrophoresis. Thus, like Vp-TDH, Vp-TRH seems to be composed of two subunits. The isoelectric point of Vp-TRH was determined to be 4.6. Vp-TRH showed lytic activities different from those of Vp-TDH on erythrocytes from various animals, especially those from calves, chickens, and sheep. The hemolytic activity of Vp-TRH was labile on heat treatment at 60 degrees C for 10 min, unlike that of Vp-TDH. The immunological similarities, but not the identities of Vp-TRH and Vp-TDH, were demonstrated by Ouchterlony, neutralization, and latex agglutination tests. Thus, we conclude that this clinical isolate of Kanagawa phenomenon-negative V. parahaemolyticus produces a new type of hemolysin that is similar, but not identical, to Vp-TDH, which is usually produced by Kanagawa phenomenon-positive V. parahaemolyticus.