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

Phylogeography of the marine pathogen, Vibrio vulnificus, revealed the ancestral scenarios of its evolution

Vibrio vulnificus is the leading cause of seafood‐associated deaths worldwide. Despite the growing knowledge about the population structure of V. vulnificus, the evolutionary history and the ancestral relationships of strains isolated from various regions around the world have not been determined. Using the largest collection of sequence and isolate data of V. vulnificus to date, we applied ancestral character reconstruction to study the phylogeography of V. vulnificus. Multilocus sequence typing data from 10 housekeeping genes were used for the inference of ancestral states and reconstruction of the evolutionary history. The findings showed that the common ancestor of all V. vulnificus populations originated from East Asia, and later evolved into two main clusters that spread with time and eventually evolved into distinct populations in different parts of the world. While we found no meaningful insights concerning the evolution of V. vulnificus populations in the Middle East; however, we were able to reconstruct the ancestral scenarios of its evolution in East Asia, North America, and Western Europe.

Spatial Heterogeneity of Vibrio spp. in Sediments of Chinese Marginal Seas

Vibrio spp. are ubiquitous marine bacteria with high metabolism flexibility and genome plasticity. Previous studies have revealed the dynamics of planktonic vibrios in relation to environmental forces, such as temperature and salinity. However, little is known about Vibrio ecology in benthic environments. Here, we elucidate the abundance, diversity, and spatial distribution of Vibrio spp. in sediments of the Chinese marginal seas, with a wide spatial range from north to south covering the Yellow Sea (YS), East China Sea (ECS), and South China Sea (SCS). Quantitative analysis showed that Vibrio spp. were most abundant in the SCS (∼9.04 × 10⁵ copies/g) compared to the YS (∼1.00 × 10⁵ copies/g) and ECS (∼8.86 × 10⁵ copies/g). Vibrio community compositions derived from Illumina sequencing of Vibrio-specific 16S rRNA genes varied significantly between sampling areas, which was reflected by a strong distance-decay pattern. The spatial distribution of Vibrio was governed by a joint effect of spatial and environmental factors (especially temperature, salinity, and SiO₃ ^2-), and their respective pure effects explained only a small fraction of the community variation. Moreover, we identified the most prominent operational taxonomic units (OTUs) that were partitioned in these sea areas. Whereas Vibrionaceae OTU20 and Photobacterium lipolyticum were prevalent in the YS, Vibrio gigantis and Photobacterium piscicola, and P. piscicola, Photobacterium lutimaris, and Photobacterium alginatilyticum were prevalent in the ECS and SCS, respectively. Our study demonstrated clear spatial heterogeneity of Vibrio spp. in sediments of the Chinese marginal seas, laying a foundation for fully understanding the marine Vibrio ecology and the ecological roles of the species.IMPORTANCE Vibrio is an important component of natural marine microbial populations in terms of pathogenicity and roles in carbon cycling. Compared to the marine pelagic environment, our knowledge of the diversity and distribution pattern of Vibrio spp. in sediment is limited. Here, we show higher Vibrio abundance in Chinese marginal seas than in other studied sediments. There was a clear spatial differentiation of Vibrio abundance and community composition in different sea areas. The benthic Vibrio community displayed a strong distance-decay pattern across a wide spatial range, which was formed under the combined effects of spatial and environmental factors. These results provide deep insights into the ecological dynamics of Vibrio and its environmental controls, facilitating a more comprehensive understanding of the marine Vibrio ecology.

Vibrio fluvialis: an emerging human pathogen

Vibrio fluvialis is a pathogen commonly found in coastal environs. Considering recent increase in numbers of diarrheal outbreaks and sporadic extraintestinal cases, V. fluvialis has been considered as an emerging pathogen. Though this pathogen can be easily isolated by existing culture methods, its identification is still a challenging problem due to close phenotypic resemblance either with Vibrio cholerae or Aeromonas spp. However, using molecular tools, it is easy to identify V. fluvialis from clinical and different environmental samples. Many putative virulence factors have been reported, but its mechanisms of pathogenesis and survival fitness in the environment are yet to be explored. This chapter covers some of the major discoveries that have been made to understand the importance of V. fluvialis.

Distribution of Vibrio alginolyticus-like species in Shenzhen coastal waters, China

We investigated the distribution of vibrios in Shenzhen coastal waters in order to obtain valuable information for the aquaculture industry and a health warning system. Quantities of vibrios from surface waters ranged from 0 to 4.40×10(4) CFUs mL(-1) in April (spring), while from 0 to 2.57×10(3) CFUs mL(-1) in September (autumn); the abundance of V. alginolyticus-like species from surface water ranged from 0 to 6.72×10(3) CFUs mL(-1) in April (spring) and from 0 to 1.28×10(3) CFUs mL(-1) in September (autumn); higher counts were observed in spring. The V. alginolyticus-like species was dominant in Shenzhen coastal waters, with the highest abundance in the clean region (stations YMK001 and GDN064) in April, suggesting that Vibrio spp. were naturally occurring bacteria in marine environments. The correlation between the abundance of vibrios (including V. alginolyticus-like species) and environmental factors varied in different regions and different seasons. There were no vibrios detected when the salinity was less than 11.15‰ in the Zhujiang River estuary, which indicated that salinity played a key role in the distribution of vibrios and V. alginolyticus-like species.

Necrotizing fasciitis of the extremities: 34 cases at a single centre over the past 5 years

BACKGROUND

Worldwide the incidence of necrotizing fasciitis (NF) is on the rise. This rapidly progressive infection is a true infectious disease emergency due to its high morbidity and mortality. The mainstay of therapy is prompt surgical debridement, intravenous antibiotics, and supportive care with fluid and electrolyte management. Because of its high mortality rate, patients are increasingly referred to burn centres for specialized wound and critical care issues.

METHODS

A retrospective chart review was performed of 34 consecutive patients over a 5-year period with NF of the upper and/or lower extremities that required surgical debridement and reconstruction.

RESULTS

The overall survival rate was 96%, with an average length of hospital stay of 64.0 ± 5.5 days. The time until the first operation was 1.3 days. The average age of the patients was 56.7 ± 10.6 years. The patients averaged 1.6 relevant comorbidities. One patient who had five comorbidities died. The affected total body surface (TBS) averaged 8.2 ± 2.1%.

CONCLUSION

Early recognition and treatment remain the most important factors influencing survival in NF. Yet, early diagnosis of the condition is difficult due to its similarities with other soft-tissue disorders. Repeated surgical debridement and incisional drainage continues to be essential for the survival. However, these infections continue to be a source of high morbidity, mortality and significant healthcare resource consumption. These challenging patients are best served with prompt diagnosis, immediate radical surgical debridement and aggressive critical care management. Referral to a major burn centre may help to provide optimal surgical intervention, wound care and critical care management.

Matriderm® in depth-adjusted reconstruction of necrotising fasciitis defects

Necrotising fasciitis (NF) and Fournier's gangrene are still a source of high morbidity and mortality and a significant health-care resource consumption. These difficult cases are increasingly being referred to burn centres for specialised wound and critical care issues. Besides the total body surface area (TBSA) affected, location, co-morbidities, age and an immediate surgical treatment are important prognostic factors. The treatment of these patients is challenging and best performed by prompt diagnosis, immediate radical surgical debridement and aggressive critical care management. Referral to a major burn centre may help provide optimal surgical intervention, wound care and critical care management.As soon as the patient is stabilised, reconstruction of the injured areas becomes the main focus. As often seen, complete loss of dermal structures needs a depth adjusted--'multilayer'--reconstruction especially in critical areas. In modern reconstructive surgery, concepts of layer-specific reconstruction, including dermal substitution have to be considered. In this article, we present our recent experiences of five patients with NF who underwent dermal reconstruction with Matriderm® not only for better skin quality but also in some cases as an alternative to flap surgery when joint capsules or tendons were exposed.

Ecology of Vibrio vulnificus and Vibrio parahaemolyticus in brackish environments of the Sada River in Shimane Prefecture, Japan

While there are several studies on the ecology of Vibrio vulnificus and Vibrio parahaemolyticus in estuarine water environments around the world, there is little information on the distribution of both organisms during the cold-weather months. Thus, we conducted a multi-year study on the ecology of both organisms in brackish environments of the Sada River, a drainage canal flowing slowly into the Japan Sea from Lake Shinji in Shimane Prefecture, Japan. Water samples were collected twice a month at five sites from August 2000 to May 2002. Both organisms were enumerated in 10 l water, 100 g sediment and 10 g shellfish by the most probable number (MPN) procedure. Isolates were confirmed as V. vulnificus using hemolysin gene PCR. During the last 7 months (including winter) of the study, water and sediment samples were also analyzed for the presence of both organisms. V. parahaemolyticus was isolated from river mouths and coastal environments of average salinity > or = 4.4+/-2.0 ppt throughout the year at cell concentrations of 10(-3) to 10(1) MPN ml(-1). Similar concentrations of V. vulnificus were isolated from coastal environments of average salinity 24.0+/-5.4 ppt, except for two times when water moved to the upper reaches due to high tide and V. vulnificus was rifted to the upper reaches. These findings suggest that both organisms are continuously distributed in the Sada estuary throughout the year regardless of water temperature.

Complete sequence of plasmid pMP1 from the marine environmental Vibrio vulnificus and location of its replication origin

A novel cryptic plasmid, pMP1, from an environmental Vibrio vulnificus MP-4 isolated from Mai Po Nature Reserve in Hong Kong, has been characterized. The 7.6-kb plasmid had guanine-cytosine content of 40.03% and encoded four open reading frames (ORFs) with >100 amino acids. The predicted protein of ORF1 contained 478 amino acids showing 29% identity and 50% similarity over 309 amino acids to the integrase of Vibrio cholerae phage VP2. ORF2 encoded a putative protein of 596 amino acids, which were 23% identity and 42% similarity over 455 amino acids to the tail tape measure protein TP901 of Chromohalobacter salexigens phage. ORF3 and ORF4 encoded putative proteins of 103 and 287 amino acids, respectively, but showed no homologies to any known proteins. Further experiments indicated that a 3.2-kb fragment from EcoRI digestion could self-replicate. Analysis indicated that a sequence upstream of ORF4 had the features characteristic of theta-type replicons: AT-rich region, six potential direct repeats (iterons) spaced approximately two DNA helical turn apart (about 23 bp), two copies of 9 bp dnaA boxes, three Dam methylation sites, and five inverted repeats. Complementation experiments confirmed that the protein encoded by ORF4 was required for plasmid replication. We propose that ORF4 encode a new type of Rep protein and pMP1 is a new type of theta plasmid.

First description of nonmotileVibrio vulnificusstrains virulent for eels

Nonmotile Vibrio vulnificus strains were isolated as pure cultures from body ulcers and internal organs of wild diseased European eels caught in a Mediterranean freshwater coastal lagoon. All 54 V. vulnificus isolates were nonmotile, indole-, ornithine decarboxilase-, mannitol- and cellobiose-positive, developed the opaque variant in culture, belonged to the O-antigenic serovar A and were highly virulent for eels by both intraperitoneal injection and immersion challenges. The nonmotile phenotype found in our V. vulnificus isolates was stable: nonmotile cells were always recovered from experimentally infected eels; no variation in the immobility of the V. vulnificus cells was observed for repeated subculture by daily passages on solid media, at different temperatures or incubation times and with or without magnesium sulfate. Many of the fla genes of Vibrio were present in the genome of the nonmotile strains (flaCDE and flaFBA for flagellins and flaH for the distal capping protein), although we observed by transmission electron microscopy that these V. vulnificus strains always lacked the polar flagellum. This is the first report on the existence of nonmotile wild-type V. vulnificus strains.

Detection and differentiation of Vibrio vulnificus in seawater and plankton of a coastal zone of the Mediterranean Sea

Vibrio vulnificus, a human and animal pathogen, is present in low numbers in the Mediterranean Sea. Seawater and plankton samples were collected from a marine coastal zone of the Straits of Messina in the Mediterranean Sea (Italy) in order to investigate V. vulnificus as free-living (>0.2 microm) and associated with small (>64 microm) and large plankton (>200 microm) utilizing cultural and molecular techniques. Characteristic colonies, grown on thiosulfate, citrate, bile salts and sucrose agar plates, were identified using a biochemical protocol system. A PCR assay was used to confirm isolates and to directly detect V. vulnificus in environmental concentrated samples. Specific primers were used to target the structural cytotoxin/hemolysin gene and the variable regions of 16S rRNA species-specific for V. vulnificus. In addition, a tri-primer PCR of 16S rRNA was used for the differentiation of V. vulnificus strains. Direct detection in marine samples was more frequent than isolation of culturable forms. All isolates were assigned to V. vulnificus biotype 1, 16S rRNA type B. These results confirm the low incidence of V. vulnificus in Mediterranean coastal waters. The isolation of cultivable forms is limited to the warmest months. 16S rRNA primers were the most sensitive molecular tool as they allowed detection of V. vulnificus in 79.1% of samples. Due to the low incidence of V. vulnificus in the Mediterranean coastal environment, its detection requires a molecular approach. The occurrence of V. vulnificus as plankton-associated confirms the role of plankton as a potential reservoir for this pathogen.

Ecology of Vibrio vulnificus in estuarine waters of eastern North Carolina

While several studies on the ecology of Vibrio vulnificus in Gulf Coast environments have been reported, there is little information on the distribution of this pathogen in East Coast waters. Thus, we conducted a multiyear study on the ecology of V. vulnificus in estuarine waters of the eastern United States, employing extensive multiple regression analyses to reveal the major environmental factors controlling the presence of this pathogen, and of Vibrio spp., in these environments. Monthly field samplings were conducted between July 2000 and April 2002 at six different estuarine sites along the eastern coast of North Carolina. At each site, water samples were taken and nine physicochemical parameters were measured. V. vulnificus isolates, along with estuarine bacteria, Vibrio spp., Escherichia coli organisms, and total coliforms, were enumerated in samples from each site by using selective media. During the last 6 months of the study, sediment samples were also analyzed for the presence of vibrios, including V. vulnificus. Isolates were confirmed as V. vulnificus by using hemolysin gene PCR or colony hybridization. V. vulnificus was isolated only when water temperatures were between 15 and 27 degrees C, and its presence correlated with water temperature and dissolved oxygen and vibrio levels. Levels of V. vulnificus in sediments were low, and no evidence for an overwintering in this environment was found. Multiple regression analysis indicated that vibrio levels were controlled primarily by temperature, turbidity, and levels of dissolved oxygen, estuarine bacteria, and coliforms. Water temperature accounted for most of the variability in the concentrations of both V. vulnificus (47%) and Vibrio spp. (48%).

16S rDNA restriction fragment length polymorphism analysis of psychrotrophic vibrios from Japanese coastal water

Restriction fragment length polymorphism (RFLP) analysis was carried out for 136 natural isolates belonging to the family Vibrionaceae. These were collected from inshore areas of Japan, mainly in winter. Twenty-eight 16S rDNA genotypes were obtained by digestion with four restriction endonucleases (HhaI, DdeI, RsaI, and Sau3AI). To estimate the genetic relationships, 53 informative fragments were scored by their presence or absence. A dendrogram was constructed using the unweighted pair group method with the arithmetic averages algorithm. Five RFLP groups (groups I to V) were obtained. Group I corresponded to Vibrio splendidus-like strains. It was confirmed that this group was not only found in Otsuchi Bay, but also in broad coastal areas of Japan. Group II strains were not identified as previously known Vibrio species. Group III strains were regarded as members of the Vibrio main group, which is a major phylogenetic group deduced from 16S rRNA gene analysis in the family Vibrionaceae. The RFLP profile indicated that Group IV strains were closely related to V. hollisae. Group V strains showed RFLP patterns which have not been observed previously. From the clustering analysis, it was concluded that group V strains were not Vibrio species. Most of the isolates studied were not identified as previously described species. It suggests that many psychrotrophic vibrios in cold marine environments remain as unknown species.Key words: Vibrio, vibrios, psychrotroph, restriction fragment length polymorphism (RFLP) analysis, Vibrio splendidus.

Complicated suppurative otitis media in a Greek diver due to a marine halophilic Vibrio sp

Halophilic vibrios are distinct from non-cholera vibrios and have been recognized increasingly as potentially pathogenic bacteria in extraintestinal infections. A case of suppurative chronic otitis media in a Greek diver with Vibrio alginolyticus recovered from an ear drainage culture, is reported. The patient received appropriate antimicrobial therapy and her hearing improved significantly after a tympanoplasty type I was performed. The association of halophilic Vibrio spp. infections with prolonged seawater contact, particularly in subtropical climates, is discussed. In swimmers with extensive exposure to salt water, individual preventive measures and aetiological treatment of ear infections seems to be required in order to reduce the severity of possible Vibrio spp. ear infections.

Contaminated marine wounds--the risk of acquiring acute bacterial infection from marine recreational beaches

An animal model was used to determine the potential for causing wound infections of bacteria isolated from marine recreational beaches in Hong Kong. Water samples were characterized physically, chemically and bacteriologically and used to inoculate artificially-induced wounds in rats. Morbidity and mortality correlated significantly (P < 0.01) with MacConkey plate counts and faecal coliform counts (membrane filtration) and inversely with salinity of the water. The majority of deaths were due to infection caused by marine and estuarine bacteria rather then enteric organisms. A total of 318 bacterial strains was isolated from the wounds and blood of animals inoculated with seawater, of which 242 were marine/estuarine (predominantly Vibrio spp., Aeromonas hydrophila and Pseudomonas putrefaciens) and 40 were enterobacteria. The virulence of the animal strains were comparable with those from clinical sources.

The human pathogenic vibrios--a public health update with environmental perspectives

Pathogenic Vibrio species are naturally-occurring bacteria in freshwater and saline aquatic environments. Counts of free-living bacteria in water are generally less than required to induce disease. Increases in number of organisms towards an infective dose can occur as water temperatures rise seasonally followed by growth and concentration of bacteria on higher animals, such as chitinous plankton, or accumulation by shellfish and seafood. Pathogenic Vibrio species must elaborate a series of virulence factors to elicit disease in humans. Activities which predispose diarrhoeal and extraintestinal infections include ingestion of seafood and shellfish and occupational or recreational exposure to natural aquatic environments, especially those above 20 degrees C. Travel to areas endemic for diseases due to pathogenic Vibrio species may be associated with infections. Host risk factors strongly associated with infections are lack of gastric acid and liver disorders. Involvement of pathogenic Vibrio species in cases of diarrhoea should be suspected especially if infection is associated with ingestion of seafood or shellfish, raw or undercooked, in the previous 72 h. Vibrio species should be suspected in any acute infection associated with wounds sustained or exposed in the marine or estuarine environment. Laboratories serving coastal areas where infection due to pathogenic Vibrio species are most likely to occur should consider routine use of TCBS agar and other detection regimens for culture of Vibrio species from faeces, blood and samples from wound and ear infections.

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)

Vibrio parahaemolyticus and other halophilic vibrios associated with seafood in Hong Kong

The summer prevalence of Vibrio parahaemolyticus and other halophilic vibrios in seafood from Hong Kong markets was investigated. Halophilic vibrios were isolated from all seven types of seafood examined, and comprised 9.1%, 8% and 6.1% of contaminating aerobic heterotrophic bacteria from mussels, clams and oysters respectively. Sucrose-positive vibrios were more common than sucrose-negative varieties. Vibrio alginolyticus was the most frequently isolated species, followed by V. parahaemolyticus, V. harveyi, V. fluvialis, V. vulnificus, V. pelagius, V. campbellii, V. spendidus and V. marinus. Mussels contained the highest concentration of V. parahaemolyticus (4.6 x 10(4)/g); oysters and clams contained 3.4 x 10(4)/g and 6.5 x 10(3)/g respectively. The ubiquity and relatively high concentrations of V. parahaemolyticus and other pathogenic vibrios in shellfish is a potential public health hazard in Hong Kong and other subtropical Asian countries.

Vibrio vulnificus septicaemia presenting as spontaneous necrotising cellulitis in a woman with hepatic cirrhosis

Vibrio vulnificus is a virulent marine organism commonly found in Hong Kong coastal waters which contaminates local sea-food. It may produce a primary septicaemia, often associated with secondary skin lesions, following ingestion of raw shell fish. We report a rapidly fatal case of primary V. vulnificus septicaemia in a 50-year-old housewife with post-hepatitic cirrhosis presenting as spontaneous necrotising cellulitis of the legs. V. vulnificus infection should be considered in patients with a history of liver disease with acute septicaemia and characteristic skin lesions.