Epidemiology, enteropathogenicity, and classification of Vi.rio parahaemolyticus

Mutation of the toxR or mshA genes from Vibrio coralliilyticus strain OCN014 reduces infection of the coral Acropora cytherea

Thermal stress increases the incidence of coral disease, which is predicted to become more common with climate change, even on pristine reefs such as those surrounding Palmyra Atoll in the Northern Line Islands that experience minimal anthropogenic stress. Here we describe a strain of Vibrio coralliilyticus, OCN014, which was isolated from Acropora cytherea during an outbreak of Acropora white syndrome (AWS), a tissue loss disease that infected 25% of the A. cytherea population at Palmyra Atoll in 2009. OCN014 recreated signs of disease in experimentally infected corals in a temperature-dependent manner. Genes in OCN014 with expression levels positively correlated with temperature were identified using a transposon-mediated genetic screen. Mutant strains harbouring transposon insertions in two such genes, toxR (a toxin regulator) and mshA (the 11th gene of the 16-gene mannose-sensitive hemagglutinin (MSHA) type IV pilus operon), had reduced infectivity of A. cytherea. Deletion of toxR and the MSHA operon in a second strain of V. coralliilyticus, OCN008, that induces acute Montipora white syndrome in a temperature-independent manner had similarly reduced virulence. This work provides a link between temperature-dependent expression of virulence factors in a pathogen and infection of its coral host.

Vibrio owensii induces the tissue loss disease Montipora white syndrome in the Hawaiian reef coral Montipora capitata

Incidences of coral disease in the Indo-Pacific are increasing at an alarming rate. In particular, Montipora white syndrome, a tissue-loss disease found on corals throughout the Hawaiian archipelago, has the potential to degrade Hawaii’s reefs. To identify the etiologic agent of Montipora white syndrome, bacteria were isolated from a diseased fragment of Montipora capitata and used in a screen for virulent strains. A single isolate, designated strain OCN002, recreated disease signs in 53% of coral fragments in laboratory infection trials when added to a final concentration of 10⁷ cells/ml of seawater. In addition to displaying similar signs of disease, diseased coral fragments from the field and those from infection trials both had a dramatic increase in the abundance of associated culturable bacteria, with those of the genus Vibiro well represented. Bacteria isolated from diseased fragments used in infection trails were shown to be descendants of the original OCN002 inocula based on both the presence of a plasmid introduced to genetically tag the strain and the sequence of a region of the OCN002 genome. In contrast, OCN002 was not re-isolated from fragments that were exposed to the strain but did not develop tissue loss. Sequencing of the rrsH gene, metabolic characterization, as well as multilocus sequence analysis indicated that OCN002 is a strain of the recently described species Vibrio owensii. This investigation of Montipora white syndrome recognizes V. owensii OCN002 as the first bacterial coral pathogen identified from Hawaii’s reefs and expands the range of bacteria known to cause disease in corals.

Tetrameric Structure of Thermostable Direct Hemolysin from Vibrio parahaemolyticus Revealed by Ultracentrifugation, Small-angle X-ray Scattering and Electron Microscopy

The thermostable direct hemolysin (TDH) is a major virulence factor of Vibrio parahaemolyticus. We have characterized the conformational properties of TDH by small-angle X-ray scattering (SAXS), ultracentrifugation and transmission electron microscopy. Sedimentation equilibrium and velocity studies revealed that the protein is tetrameric in aqueous solvents. The Guinier plot derived from SAXS data provided a radius of gyration of 29.0 A. The elongated pattern with a shoulder of a pair distance distribution function derived from SAXS data suggested the presence of molecules with an anisotropic shape having a maximum diameter of 98 A. Electron microscopic image analysis of the negatively stained TDH oligomer showed the presence of C(4) symmetric particles with edge and diagonal lengths of 65 A and 80 A, respectively. Shape reconstruction was carried out by ab initio calculations using the SAXS data with a C(4) symmetric approximation. These results suggested that the tetrameric TDH assumes an oblate structure. The hydrodynamic parameters predicted from the ab initio model differed slightly from the experimental values, suggesting the presence of flexible segments.

Gastrointestinal infections

Advances in public health have reduced the risk of contracting certain enteric diseases, but many remain, and new pathogens have emerged and/or recently have been discovered. The pathogenic agents are varied and consist of a variety of bacteria and select viruses and parasites. Selected use of microbiologic assays to detect these pathogens is encouraged. When tests are ordered non-judiciously, costs rapidly accrue. The age of the patient, time of year, travel history, and clinical presentation all provide clues to the etiologic agent. Microbiologic assays should be used judiciously to confirm or exclude the likely infectious agents.

Electrophoretic and chemical characterization of lipopolysaccharides of Vibrio parahaemolyticus

Lipopolysaccharides (LPSs) isolated from three Kanagawa-positive and three negative strains of Vibrio parahaemolyticus were characterized by using electrophoretic, immunochemical, and chemical methods. The results of this study indicated that the LPSs of all six strains of V. parahaemolyticus examined did not have an O-specific side chain. These V. parahaemolyticus LPSs appeared to have molecular weights similar to that of the rough-type (Ra) LPS of Salmonella typhimurium TV-119 and might just contain lipid A and a core region. However, the microheterogeneity of V. parahaemolyticus LPS observed was greater than that of S. typhimurium LPS. The profile of V. parahaemolyticus LPS consisted of closely spaced triplet or quadruplet bands, but that of S. typhimurium consisted of doublet bands. Slower-moving bands appeared on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels only when large amounts of V. parahaemolyticus LPS were loaded. These bands were proven to be the aggregates of the fastest-moving low-molecular-weight bands by re-electrophoresis. The banding pattern of V. parahaemolyticus LPSs produced on nitrocellulose membranes by immunoblotting indicated that the V. parahaemolyticus LPSs did not have an O-specific side chain. The low ratio of total carbohydrate to lipid A of V. parahaemolyticus LPSs also suggested that they were like rough-type LPS. The mobility and profile of V. parahaemolyticus LPS on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel and its chemical composition were closely related to the serotype of a specific strain but not with the Kanagawa phenomenon.

Outbreaks of diarrhoeal illness on passenger cruise ships, 1975-85

We reviewed data from the Vessel Sanitation Program (VSP), established by the US Public Health Service in 1975, to describe the epidemiology of shipboard diarrhoeal outbreaks, determine the risk of outbreak-related illness among cruise ship passengers, and evaluate changes in rates and patterns of shipboard diarrhoeal illness since the VSP was implemented. When the programme began, none of the cruise ships passed periodic VSP sanitation inspections; since 1978, more than 50% of ships have met the standard each year. On cruises lasting 3-15 days and having at least 100 passengers, diarrhoeal disease outbreaks investigated by the Centers for Disease Control decreased from 8.1 to 3.0 per 10 million passenger days between 1975-79 and 1980-85. The proportion of outbreaks due to bacterial pathogens (36%) did not change. Seafood cocktail was implicated in 8 of 13 documented food-borne outbreaks. The risk of diarrhoeal disease outbreaks on cruise ships appears to have decreased since implementation of the VSP but has not been eliminated.

Phosphate regulation of gene expression in Vibrio parahaemolyticus

The synthesis of a major outer membrane protein, OmpP, in Vibrio parahaemolyticus was induced by growth in media deficient in phosphate. The gene, ompP, encoding this protein was cloned. Synthesis of OmpP in Escherichia coli was regulated by the availability of phosphate, and this control required the function of pho regulatory genes of E. coli. Analysis of gene fusion strains constructed by mutagenesis with transposon mini-Mulux revealed that ompP was transcriptionally regulated in V. parahaemolyticus. Impaired growth of a strain with an ompP defect was observed in media which contained large linear polyphosphates as the phosphate source. This and other evidence suggested that OmpP functions as a porin channel for the entry of phosphate into the cell. A number of other proteins or activities were induced by phosphate limitation including hemolysin, phospholipase C, and phosphatase activities. A regulatory locus controlling expression of phosphate-regulated genes was identified and cloned. This regulatory locus cloned from V. parahaemolyticus was shown to complement E. coli strains with defects in pho regulatory genes.

Occurrence and distribution of halophilic vibrios in subtropical coastal waters of Hong Kong

The summer occurrence and distribution of halophilic vibrios in the subtropical coastal waters of Hong Kong were investigated. The density of vibrios in six sample sites ranged from 90 to 6,700 per ml, which made up 0.41 to 40% of the total bacterial populations of these sample sites. The sucrose-positive vibrios were found to be much more common (88% of total vibrios) than the sucrose-negative ones. A total of 48 strains belonging to six Vibrio species were fully characterized. Among these, Vibrio alginolyticus was the most frequently isolated, followed by V. parahaemolyticus, V. harveyi, V. vulnificus, V. campbellii, and V. fluvialis. The finding that eight of the nine strains of V. harveyi showed a positive Kanagawa reaction warrants further study.

Vibrio parahaemolyticus and related halophilic Vibrios

Approximately 30 years have elapsed since Dr. Fujino's original discovery that Vibrio parahaemolyticus (then termed Pasteurella parahemolytica) was the cause of "summer diarrhea" in Japan. Since that finding, V. parahaemolyticus has been established as a cause of gastroenteritis in numbers and places approaching global proportions. It has been isolated in marine and estuarine areas almost worldwide and despite its halophilic nature, V. parahaemolyticus has been isolated from saline-free waters. The relationship of this organism to the environment reveals a close association with other marine organisms especially copepods on which the Vibrios depend for survival in winter months and growth in summer months. There is a uniquely provocative disparity between human strains of V. parahaemolyticus which are Kanagawa phenomenon (KP) positive and the environmental strains which to a large extent are KP negative, the significance being that pathogenicity is measured according to the Kanagawa phenomenon (hemolytic activity) reaction. The hemolysin of the pathogenic strains is a thermostable, cardiotoxic protein, which thus far has not been implicated in the mechanism(s) which causes human gastroenteritis. The interest in this organism has been widened in recent years by the finding that similar organisms, V. alginolyticus, lactose positive vibrios and group F vibrios also cause serious disease in humans.

A comparative study of the sugar composition of O-antigenic lipopolysaccharides isolated from Vibrio alginolyticus and Vibrio parahaemolyticus

A comparative study of the sugar composition of O-antigenic lipopolysaccharides (LPS) isolated from Vibrio alginolyticus and those from V. parahaemolyticus was carried out. 3-Deoxy-D-mannooctulosonic acid, 2-keto-3-deoxy octonate (KDO), a regular sugar constituent of gram-negative bacterial LPS, was totally absent from LPS of all V. alginolyticus strains examined as it was from those of V. parahaemolyticus. Furthermore, a KDO-like thiobarbituric acid test-positive substance, identical with that of either V. parahaemolyticus 07 or 012, was also found in LPS from three strains, 505-78, 905-78, and 1013-79 (designated tentatively as group I), out of the five strains of V. alginolyticus tested. LPS from the members of group I contained, as component sugars, glucose, galactose, L-glycero-D-manno-heptose, glucosamine, galactosamine, the KDO-like substance, and an unidentified amino sugar P1. Thus, LPS of the members of group I possessed a similar sugar composition which is similar to that of LPS from either V. parahaemolyticus 97 or 012. LPS of strain 1027-79, one of the other two strains (designated tentatively as group II), contained as component sugars, glucose, L-glycero-D-mannoheptose, glucosamine, galactosamine, galactosamine, and the other unidentified amino sugar P2, while LPS of strain 53-79, the other member of group II, contained galactose as an additional component. The results indicate that LPS of strain 1027-79 has a sugar composition similar to that of V. parahaemolyticus 09 LPS.

Experimental pathogenicity and mortality in ligated ileal loop studies of the newly reported halophilic lactose-positive Vibrio sp

Laboratory animals were challenged subcutaneously, intraperitoneally, and intravenously with the halophilic lactose-positive Vibrio. Intraperitoneal inocula of 10(8) organisms proved to be rapidly lethal in mice, rats, and hamsters. The 50% lethal doese in ICR strain mice was estimatd to be 8 X 10(5) live cells, injected intraperitoneally or subcutaneously. Subtaneous inocula in mice resulted in severe local infections, characterized by gross edema, and for those animals surviving longer than 48 h, tissue necrosis. Intravenous, intraperitoneal, and subcutaneous injections of 10(8) cells in mice resulted in death within 3 to 6 h. These animals rapidly developed Vibrio bacteremia after injections. V. parahaemolyticus, studied for comparative purposes, produced no morbidity or mortality when injected subcutaneously. Injections of live lactose-positive Vibrio into ligated ileal loops in rats and rabbits consistently proved to be lethal with a high-density bacteremia resulting.

Halophilic Vibrio species isolated from blood cultures

The Special Bacteriology Section of the Center for Disease Control has received 38 cultures of a halophilic bacterium which apparently unnamed. On the basis of the minimal characteristics of Vibrio species proposed by Hugh and Sakazaki, this bacterium belongs to the genus Vibrio. The unnamed species can be differentiated from Vibro parahaemolyticus by a lower tolerance for sodium chloride (NaC1) and the fermentation of lactose. The failure to ferment sucrose is an additional characteristic which differentiates these organisms from V. alginolyticus. Of 33 unnamed species strains tested, all were sensitive to penicillin, ampicillin, carbenicillin, cephalothin, chlorapmphenicol, gentamicin, tetracycline, rifampin, nitrofurantoin, and sulfisoxazole by agar diffusion and agar dilution tests. The sources of isolation of the cultures of the unnamed species suggest that it is a clinically important organism. Twenty strains were isolated remaining cultures were isolated from localized infections of the extremities. In contrast, only 2 of 60 cultures of V. parahaemolyticus and V. alginolyticus received in our laboratory as human isolates from extra-intestinal sources were isolated from blood.

Polynucleotide sequence relationships among Japanese and American strains of Vibrio parahaemolyticus

Polynucleotide sequence relationships between two reference Vibrio parahaemolyticus strains isolated from Japanese and American gastroenteritis patients were investigated by use of (32)P-DNA/DNA reassociation in free solution. In addition, these strains were similarly compared with 22 other strains of estuarine and marine vibrios, including 11 strains previously identified as V. parahaemolyticus (2 Japanese, 1 of unknown location, and 8 American strains obtained from diverse geographical locations and sources in North America), 3 strains of V. alginolyticus, and 8 of Vibrio spp. Deoxyribonucleic acid (DNA) from the Japanese and American gastroenteritis isolates showed high relative levels of intraspecific duplex formation (92 to 93%) when reassociated, reciprocally, at 60 C. Heterologous DNA duplexes exhibited thermal elution midpoint [Tm(e)] values comparable to those obtained from homologous duplexes (88.0) when thermally eluted from hydroxyapatite, thus indicating high base-pair complementarity. Other V. parahaemolyticus strains showed DNA homologies of 85% or greater, with correspondingly high Tm(e) values (86.0 to 88.0) for the heteroduplexes formed. DNA of two of three V. alginolyticus strains (ATCC 17749 and 166-70) was 55 to 60% homologous to reference V. parahaemolyticus DNA preparations; Vibrio sp. strain 5144 (originally classified as V. parahaemolyticus biotype 2 and subsequently as V. alginolyticus strain 5144) showed only 24 to 26% DNA homology to the same reference DNA. These data provide evidence that Vibrio sp. strain 5144 is genetically distinct from the other V. alginolyticus strains used in this study. Three bioluminescent strains thought to be closely related to V. parahaemolyticus demonstrated only 24 to 31% DNA homology to the reference V. parahaemolyticus DNA. These data firmly establish the existence in some Atlantic and Gulf Coast estuaries of organisms genetically very similar to V. parahaemolyticus, the causative agent of "shirasu" food poisoning in Japan.

Taxonomy of marine bacteria: Beneckea parahaemolytica and Beneckea alginolytica

A collection of 169 strains, including 91 obtained from cases of gastroenteritis and 41 from localized tissue infections and infections of the eye and ear, was submitted to an extensive nutritional, physiological, and morphological characterization. The nutritional and physiological data obtained from these strains, as well as data for strains of other species of the genus Beneckea, were submitted to a numerical analysis which grouped the strains into clusters on the basis of phenotypic similarity. Strains from cases of gastroenteritis formed a group of three clusters which linked at a similarity value of 68%. These three clusters could not, however, be separated from each other by universally positive or negative traits, and on the basis of their overall phenotypic similarity were assigned to a single species, B. parahaemolytica. The majority of the strains from human, nonenteric sources segregated into two distinct clusters, one designated B. alginolytica and the other unassigned with respect to species (group C-2). B. parahaemolytica, B. alginolytica, and group C-2 could be readily distinguished from one another as well as from the remaining species of the genus Beneckea by multiple, unrelated, phenotypic traits. Activities of selected enzymes of glucose and gluconate catabolism in cell-free extracts of B. parahaemolytica, B. alginolytica, and group C-2 suggested that these organisms utilized glucose primarily via the Embden-Meyerhof pathway and gluconate primarily via the Entner-Doudoroff pathway. Similar results were observed in the other members of the genus Beneckea.

Deoxyribonucleic acid relationships among marine vibrios

The deoxyribonucleic acid (DNA) relationships of 80 strains identified either as Vibrio parahaemolyticus, V. alginolyticus, and V. anguillarum, or as allied marine vibrios were delineated by DNA-DNA competition experiments as well as by measuring the thermal stabilities of the DNA-DNA duplexes formed in direct binding studies. The tested strains included isolates from Japan, Europe, and the United States. The V. parahaemolyticus and V. alginolyticus groups showed an average of 67% homology to one another and 30% to strains of V. anguillarum. Significantly, a number of the isolates from the Pacific Northwest which had been previously identified as V. parahaemolyticus based on morphological, biochemical, and serological evidence were shown either to be strains of V. anguillarum or to belong to as yet unnamed groups. Most strains isolated from diseased salmon in the Pacific Northwest proved to be virtually identical with V. anguillarum type C by DNA homology experiments, thereby differentiating them from similar strains isolated from diseased herring and occasionally from salmon. The latter Pacific Northwest isolates fell into two distinct genotypic groups. A plot of the per cent homology by competition versus the difference in the thermal stabilities of heterologous and homologous duplexes (DeltaT(m,e)) between the same DNA species shows a linear decline in homology of 4.25% per degree of DeltaT(m,e). The use of this relationship for estimating the percentage of the mispaired bases distinguishing DNA preparations directly from competition experiments is discussed.

Taxonomy of marine bacteria: the genus Beneckea

One-hundred-and-forty-five isolates of marine origin were submitted to an extensive physiological, nutritional, and morphological characterization. All strains were gram-negative, facultatively anaerobic, straight or curved rods which were motile by means of flagella. Glucose was fermented with the production of acid but no gas. Sodium but no organic growth factors were required. None of the strains were able to denitrify or fix molecular nitrogen. The results of nutritional and physiological tests were submitted to a numerical analysis. On the basis of phenotypic similarity, nine groups were established. These groups could be distinguished from one another by multiple, unrelated, phenotypic traits. Six groups which had deoxyribonucleic acid (DNA) containing 45 to 48 moles per cent guanine plus cytosine (GC) were assigned to a redefined genus Beneckea. All of the strains in this genus, when grown in liquid medium, had a single, polar flagellum. When grown on a solid medium, many strains had peritrichous flagella. Two groups were similar to previously described species and were designated B. alginolytica and B. natriegens. The remaining four groups were designated B. campbellii, B. neptuna, B. nereida, and B. pelagia. An additional group of phenotypically similar strains having the properties of the genus Beneckea was not included in the numerical analysis. These strains were readily separable from species of this genus and were designated B. parahaemolytica. Of the remaining groups, one was identified as Photobacterium fischeri. The other group (B-2) which had about 41 moles% GC content in its DNA could not be placed into existing genera.

Occurrence of Vibrio parahaemolyticus in estuarine waters and oysters of New Hampshire

Vibrio parahaemolyticus was isolated from water and oysters collected from seven different sampling stations in the Great Bay and Little Bay estuarine areas of New Hampshire. The morphological and biochemical characteristics of 50 isolates conformed in general to those described for this organism in the literature. All isolates produced hemolysis on blood-agar. To date, there have been no reports of V. parahaemolyticus food poisoning outbreaks due to the consumption of fish or shellfish harvested from this estuarine region.

Polyphasic taxonomy of the genus vibrio: numerical taxonomy of Vibrio cholerae, Vibrio parahaemolyticus, and related Vibrio species

A set of 86 bacterial cultures, including 30 strains of Vibrio cholerae, 35 strains of V. parahaemolyticus, and 21 representative strains of Pseudomonas, Spirillum, Achromobacter, Arthrobacter, and marine Vibrio species were tested for a total of 200 characteristics. Morphological, physiological, and biochemical characteristics were included in the analysis. Overall deoxyribonucleic acid (DNA) base compositions and ultrastructure, under the electron microscope, were also examined. The taxonomic data were analyzed by computer by using numerical taxonomy programs designed to sort and cluster strains related phenetically. The V. cholerae strains formed an homogeneous cluster, sharing overall S values of >/=75%. Two strains, V. cholerae NCTC 30 and NCTC 8042, did not fall into the V. cholerae species group when tested by the hypothetical median organism calculation. No separation of "classic" V. cholerae, El Tor vibrios, and nonagglutinable vibrios was observed. These all fell into a single, relatively homogeneous, V. cholerae species cluster. V. parahaemolyticus strains, excepting 5144, 5146, and 5162, designated members of the species V. alginolyticus, clustered at S >/=80%. Characteristics uniformly present in all the Vibrio species examined are given, as are also characteristics and frequency of occurrence for V. cholerae and V. parahaemolyticus. The clusters formed in the numerical taxonomy analyses revealed similar overall DNA base compositions, with the range for the Vibrio species of 40 to 48% guanine plus cytosine. Generic level of relationship of V. cholerae and V. parahaemolyticus is considered dubious. Intra- and intergroup relationships obtained from the numerical taxonomy studies showed highly significant correlation with DNA/DNA reassociation data.

A survey on the occurrence of Vibrio parahaemolyticus on fish and shellfish, marketed in the Netherlands

A survey was carried out on the occurrence of Vibrio parahaemolyticus on fish and shellfish, as sold in The Netherlands.THE OPTIMAL MODE OF DETECTION OF THIS BACTERIUM APPEARED TO BE: (i) enrichment of swabs taken from the surface and the gills in freshly prepared meat broth with 5% NaCl; (ii) streaking onto Teepol bromothymol blue agar (BTB) and taurocholate bromothymol blue sucrose agar (TCBS); (iii) confirmation of suspect colonies by testing for mode of growth in butts/slants of a Kligler type glucose sucrose iron thiosulphate agar, formation of indole in 2% NaCl 2% trypticase water, anaerobic utilization of starch in the presence of 5% NaCl and oxidase reaction according to Kovacs (1956).A total of 407 samples, stemming from 17 types of fish and shellfish, taken at three fish shops, was examined by this technique. Only one specimen, i.e. a haddock, was found to contain V. parahaemolyticus. This contamination rate of approximately 0.3% correlates well with data found earlier for fish landed in Northern Germany.

Morphological, cultural, biochemical, and serological comparison of Japanese strains of Vibrio parahemolyticus with related cultures isolated in the United States

Morphological, cultural, biochemical, and serological characteristics of 79 strains of Vibrio parahemolyticus isolated from patients suffering from gastroenteric disease in Japan were compared with 17 suspected V. parahemolyticus cultures isolated from wound infections and 14 nonpathogenic vibrios isolated from an estuarine environment in the United States. These groups were differentiated on the basis of several key reactions which included: the range of growth temperature and salt tolerance; the production of catalase and acetoin; the hydrolysis of starch; the fermentation and utilization as single carbon source of sucrose, cellobiose, and arabinose; and the ability to swarm on 1% agar. The separation of the groups on the basis of cultural and biochemical analyses was confirmed by means of slide agglutinations with specific anti-K antisera. The results of this study strongly suggest that the wound infection isolates are V. parahemolyticus species which are easily distinguished from the nonpathogenic estuarine vibrios.