Ecological fitness and virulence features of Vibrio parahaemolyticus in estuarine environments

Vibrio parahaemolyticus is a commonly encountered and highly successful organism in marine ecosystems. It is a fast-growing, extremely versatile copiotroph that is active over a very broad range of conditions. It frequently occurs suspended in the water column (often attached to particles or zooplankton), and is a proficient colonist of submerged surfaces. This organism is an important pathogen of animals ranging from microcrustaceans to humans and is a causative agent of seafood-associated food poisoning. This review examines specific ecological adaptations of V. parahaemolyticus, including its broad tolerances to temperature and salinity, its utilization of a wide variety of organic carbon and energy sources, and its pervasive colonization of suspended and stationary materials that contribute to its success and ubiquity in temperate and tropical estuarine ecosystems. Several virulence-related features are examined, in particular the thermostable direct hemolysin (TDH), the TDH-related hemolysin (TRH), and the type 3 secretion system, and the possible importance of these features in V. parahaemolyticus pathogenicity is explored. The impact of new and much more effective PCR primers on V. parahaemolyticus detection and our views of virulent strain abundance are also described. It is clear that strains carrying the canonical virulence genes are far more common than previously thought, which opens questions regarding the role of these genes in pathogenesis. It is also clear that virulence is an evolving feature of V. parahaemolyticus and that novel combinations of virulence factors can lead to emergent virulence in which a strain that is markedly more pathogenic evolves and propagates to produce an outbreak. The effects of global climate change on the frequency of epidemic disease, the geographic distribution of outbreaks, and the human impacts of V. parahaemolyticus are increasing and this review provides information on why this ubiquitous human pathogen has increased its footprint and its significance so dramatically.

     

Characteristics of Escherichia coli grown in bay water as compared with rich medium

Membrane-filtered bay water can support a certain degree of growth of Escherichia coli organisms isolated from the bay water or from sewage. The effect of the growth medium (bay water versus rich medium) on sensitivities to antimicrobial agents and cell envelope proteins was studied in many of these strains. Bay water-grown cells were less sensitive to bacteriophages and colicins, but were more sensitive to heavy metals and detergents as compared with rich-medium-grown cells. These results indicated that the cell envelope composition of the bay water-grown cells could be modified, resulting in altered susceptibility to various antimicrobial agents. An analysis of cell envelope proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that cells from rich-medium-grown cultures contained two or three major outer membrane proteins, whereas in bay water-grown cells, the OmpF protein was greatly reduced.     

Effect of fecal pollution on Vibrio parahaemolyticus densities in an estuarine environment

Vibrio parahaemolyticus densities in the Narragansett Bay, R.I., estuary were found to significantly correlate with the level of fecal pollution in the water. Results of field investigations showed a definite association between the levels of this organism and those of Escherichia coli, Clostridium perfringens, and enterococci. Densities of V. parahaemolyticus were greatest in the near-surface waters of contaminated areas and decreased sharply with both the distance from the sources of fecal pollution and the depth of the water column. A positive association with the amount of particulate matter in the water and specifically with its zooplankton content also was found. No association was obtained with any of the physical or chemical parameters examined except dissolved oxygen. The results of laboratory studies on the growth of V. parahaemolyticus in collected estuarine waters were consistent with the field observations in that nutrients in sewage did not directly produce any increase in natural or inoculated levels of the organism. Of several particulates added to the water, only chitin and net zooplankters (live or dead) supported the growth of V. parahaemolyticus. The addition of sewage to the water had no measurable effect, whether or not the various particulates also were present. The data show that wastewater effluents have an effect on V. parahaemolyticus densities in this estuary and indicate that the effect is indirect, probably mediated by biostimulation of the food chain and manifested at the level of the microfauna.     

Vibrio parahaemolyticus in Rhode Island coastal ponds and the estuarine environment of narragansett bay

Quantification of the abundance of Vibrio parahaemolyticus in water and oysters from Rhode Island showed the presence of environmental strains and low levels of potentially pathogenic strains when water temperatures were ≥18°C, with peak levels in late July to early August. A higher abundance of the trh gene than of the tdh gene was observed.     

Effect of fecal pollution on Vibrio parahaemolyticus densities in an estuarine environment.

Vibrio parahaemolyticus densities in the Narragansett Bay, R.I., estuary were found to significantly correlate with the level of fecal pollution in the water. Results of field investigations showed a definite association between the levels of this organism and those of Escherichia coli, Clostridium perfringens, and enterococci. Densities of V. parahaemolyticus were greatest in the near-surface waters of contaminated areas and decreased sharply with both the distance from the sources of fecal pollution and the depth of the water column. A positive association with the amount of particulate matter in the water and specifically with its zooplankton content also was found. No association was obtained with any of the physical or chemical parameters examined except dissolved oxygen. The results of laboratory studies on the growth of V. parahaemolyticus in collected estuarine waters were consistent with the field observations in that nutrients in sewage did not directly produce any increase in natural or inoculated levels of the organism. Of several particulates added to the water, only chitin and net zooplankters (live or dead) supported the growth of V. parahaemolyticus. The addition of sewage to the water had no measurable effect, whether or not the various particulates also were present. The data show that wastewater effluents have an effect on V. parahaemolyticus densities in this estuary and indicate that the effect is indirect, probably mediated by biostimulation of the food chain and manifested at the level of the microfauna.     

Vibrio parahaemolyticus and Vibrio vulnificus in South America: water,seafood and human infections

The bacterial species, Vibrio parahaemolyticus and Vibrio vulnificus, are ubiquitous in estuaries and coastal waters throughout the world, but they also happen to be important human pathogens. They are concentrated by filter‐feeding shellfish which are often consumed raw or undercooked, providing an important potential route of entry for an infective dose of these bacteria. Vibrio parahaemolyticus can cause abdominal cramping, nausea, diarrhoea, vomiting, chills and fever. Vibrio vulnificus can cause similar gastrointestinal‐related symptoms, but can also spread to the bloodstream, resulting in primary septicaemia, and it can also cause disease via wound infections. The objective of this article is to summarize, for the first time, the incidence and importance of V. parahaemolyticus and V. vulnificus in South America, in environmental waters and seafood, especifically molluscan shellfish, as well as human infection cases and outbreaks. It appears that infections from V. parahaemolyticus have been more strongly related to shellfish ingestion and have been more frequently reported on the Pacific coast of South America. Conversely, V. vulnificus has been more frequently acquired by water contact with open wounds and its presence has been more heavily reported along the Atlantic coast of South America, and while documented to cause serious mortality, have been relatively few in number. The impacts of El Nino Southern Oscillation (ENSO) have been observed to cause an increase in V. parahaemolyticus outbreaks on the Pacific coast of South America. The implementation of a regulated monitoring approach, along with the use of faster, more accurate and virulence‐specific detection approaches, such as PCR confirmation, should be considered to detect the presence of pathogenic Vibrio strains in environmental and seafood samples for protection of public health. Furthermore, improved clinical surveillance with suspected cases should be implemented. This review highlights the need for more research and monitoring of vibrios in South America, in water, shellfish and clinical samples.     

Resuscitation of viable but non-culturable Vibrio parahaemolyticus in a minimum salt medium

Vibrio parahaemolyticus is food-borne pathogen prevalent in Asian countries. This work analyzes factors that influence the resuscitation of the viable but nonculturable (VBNC) state in this bacterium. The MMS-0.5% NaCl medium alone limited cell multiplication, and in this medium, resuscitation was successful when the temperature was upshifted to 25 degrees C but not 37 degrees C. Chloramphenicol inhibition experiments revealed that protein synthesis in the first 24 h of temperature upshift was critical in determining the success of the three-day resuscitation period. The VBNC state induction period and the age of the VBNC cells for successful resuscitation were strain-dependent. Results of this work facilitate further physiological and pathological study of the VBNC state in this pathogen.     

Comparison of hemolysins of Vibrio cholerae non-O1 and Vibrio hollisae with thermostable direct hemolysin of Vibrio parahaemolyticus

Hemolysin (Vh-rTDH) produced by Vibrio hollisae and hemolysin (NAG-rTDH) produced by Vibrio cholerae non-O1 were characterized and compared with hemolysin (Vp-TDH) produced by Vibrio parahaemolyticus. These three hemolysins are each composed of two subunits and have similar, but not identical, molecular weights. The amino acid compositions of Vp-TDH and NAG-rTDH are similar, but are different from that of Vh-rTDH. The three hemolysins showed similar lethal toxicities to mice. The effects of temperature on hemolysis and the time dependencies of hemolysis by the three hemolysins were similar. The three were concluded to be immunologically related, but not identical, and to have common and also unique antigenic determinants.     

Effects of pH of the medium on flagellation of Vibrio parahaemolyticus.

Formation of the lateral flagella by Vibrio parahaemolyticus was inhibited under an alkaline condition of the medium. However, flagellation of the polar monotrichous flagellum was not affected in the same condition. Flagellation of the lateral flagella depended on the pH of the medium.     

Serovars of Vibrio parahaemolyticus

Seashore water samples collected along the coastline in Bulgaria and Rumania contained in large numbers OK serovars of V. parahaemolyticus; some of these had been isolated repeatedly over an extended time period: 01 K32, 03 K30, 03 K48, 04 K37, 04 K53, 05 K17, 05 K30. The serovar 05 K17 was virtually present in all water samples and was also isolated from a case of purulent ear infection in a child from Burgas. In contrast, strains recovered from Asian and African coastal water had different K antigens and were never identified in Europe. Two strains of V. parahaemolyticus (serovars 05 K15 and 07 K10) had positive swarming growth resembling that of V. alginolyticus. The first of these was Kanagawa-positive and was isolated from a case of severe diarrhea in Brazzaville. Vibrio parahaemolyticus isolates came from marine or brackish water specimens collected on sand banks, 3 strains were recovered from marine or brackish water in Africa. Vibrio harveyi, a sucrose-negative species important from differential diagnostic aspects, has been isolated from seashore water samples collected on coarse-sand or pebbly beaches.     

副溶血弧菌的致病机制

副溶血性弧菌是引发微生物食源性疾病的首要病原菌,其在临床上主要引起3种疾病,即胃肠炎、伤口感染和败血症。经过多年的研究,人们对副溶血性弧菌的致病机制有了一定的认识。我们着重介绍副溶血性弧菌的主要毒力因子、毒力基因表达调控及常用的毒力表型研究方法。     

Effects of pH of the medium on flagellation of Vibrio parahaemolyticus.

Formation of the lateral flagella by Vibrio parahaemolyticus was inhibited under an alkaline condition of the medium. However, flagellation of the polar monotrichous flagellum was not affected in the same condition. Flagellation of the lateral flagella depended on the pH of the medium.     

Comparison of different biochemical and molecular methods for the identification of Vibrio parahaemolyticus

AIMS: Multicentre evaluation of biochemical and molecular methods for the identification of Vibrio parahaemolyticus. METHODS AND RESULTS: For the biochemical identification methods, API 20E and API 20NE and Alsina's scheme were evaluated in intra- and interlaboratory tests in order to determine the accuracy and concordance of each method. Both in intra- and interlaboratory tests, the Alsina's scheme showed the highest sensitivity (86% of correct identifications in the interlaboratory test). False-positive results were obtained by all methods (specificity was 95% for API 20E, 73% for API 20NE and 84% for Alsina's scheme) and concordance varied from 65% of API 20NE to 84% of API 20E. For the molecular identifications, polymerase chain reaction (PCR) for the detection of toxR gene, tl gene and pR72H fragment were tested on 30 strains by two laboratories. The PCR for toxR showed the highest inclusivity (96%), exclusivity (100%) and concordance (97%). CONCLUSIONS: Among the biochemical identification methods tested, the Alsina's scheme gave more reliable results; however, in order to avoid false-positive results, all the biochemical identifications should be confirmed by means of molecular methods. SIGNIFICANCE AND IMPACT OF THE STUDY: Availability of an efficient identification method of Vibrio parahaemolyticus to use in official control of fisheries products.     

Characterization and distribution of Vibrio alginolyticus and Vibrio parahaemolyticus isolated in Indonesia

Previous studies have shown that Vibrio alginolyticus and Vibrio parahaemolyticus can be isolated from similar types of marine samples. In this report, the results of an examination of 567 V. alginolyticus and V. parahaemolyticus strains, isolated from seawater in Jakarta Bay and from more than 30 types of seafood from markets in Jakarta, Indonesia, are presented. Most isolates were from mackerel, shrimp, or squid. Numerical taxonomic analyses clustered 337 isolates and three V. alginolyticus reference strains at S greater than or equal to 80%. These strains produced acid from sucrose, but only approximately 80% produced acetoin or grew in the presence of 10% NaCl. The frequency of occurrence of V. alginolyticus in seawater samples ranged from 0% (in February and March 1972) to 100% (in September and December 1972) and was highest in seafood samples from August to December 1972. A second cluster of 230 isolates and seven V. parahaemolyticus reference strains was observed at S greater than or equal to 82%. These strains did not produce acetoin or acid from sucrose, and approximately 20% grew in the presence of 10% NaCl. V. parahaemolyticus was detected in seawater samples each month, with the highest frequency of occurrence (83.3%) in May 1972. Twenty-nine K antigen serotypes were demonstrated in V. parahaemolyticus isolates, and another 40% were untypable. The modal antibiotic resistance pattern for each species included five drugs. Only 12% of the V. parahaemolyticus strains were Kanagawa positive, and 10% elicited fluid accumulation in ligated rabbit ileal loops. All of the 7 V. alginolyticus strains and 94 (70%) of the V. parahaemolyticus strains tested killed mice when inoculated intraperitoneally.(ABSTRACT TRUNCATED AT 250 WORDS)