Introduction:Vibrios are naturally occurring bacteria indigenousto marine and estuarine waters. Of the 65 knownspecies of these bacteria, several are pathogenic toboth marine animals and humans. A total of twelvedifferent Vibrio spp. are known to be pathogenicto man, but the following four species account formost of the human infections. Depending on thespecies involved and the nature of the exposure,infection can be asymptomatic, cause mild tosevere gastroenteritis, or result in septicemia(blood infection) or wound and soft tissueinfection.

1. V. vulnificus: contracted primarily byingestion of seafood or contact with marinewaters resulting in gastroenteritis; andwound infections, often leading tosepticemia and death.

2. V. cholerae: contracted primarily byingestion of contaminated water, resultingin gastroenteritis, often leading to death.

3. V. parahaemolyticus: contracted primarilyby ingestion of contaminated marine foods,often leading to gastroenteritis.

4. V. alginolyticus: contracted primarily bycontact with marine waters, leading to skinand ear infections.

All four of these pathogenic Vibrio spp. have beendocumented to cause human infections in Hawaii.V. vulnificus infections have recently resulted intwo deaths related to exposure to coastal waters.One death occurred on the Big Island and asecond death occurred on Oahu. V. choleraeinfections have also been documented in Hawaiithough the source of these infections has not been

P R O J E C T B U L L E T I N S E P T E M B E R, 2 0 1 1

determined. Infections of V. parahaemolyticus and V.alginolyticus have also been reported in Hawaii.

No approved methods exist for the recovery of humanpathogenic Vibrio bacteria from environmental waters,thus the risk of aquiring Vibrio infections from contactwith these waters has never been determined.Therefore water quality standards, which may helppredict the presence of potentially pathogenic Vibriospp., have not been established.

Project Goals and Experimental Approach:The goal of this study is to determine the prevalence offour human pathogenic Vibrio spp. (V. cholerae, V.vulnificus, V. parahaemolyticus, V. alginolyticus) infour categories of coastal water environments ofHawaii, and to determine the potential risk that thesepathogens may pose to people who use these coastalwaters for recreational purposes.

Gayatri Vithanage,former Microbiologydoctoral graduateresearch assistant withWRRC (nowgraduated) conductedthis study as part of herdissertation research.The experimentaldesign of her studywas to determine theprevalence of humanpathogenic Vibrio spp.in the following fourcategories of coastal waters:

1) Primary swimming sites on Oahu; this categoryincluded popular beach sites designated forpublic swimming. The waters at these sites are

Assessing Concentrations and Potential Public Health Significance of FourHuman Pathogenic Marine Vibrio spp. in Hawaiian Coastal Water Environments

Gayatri Vithanage

characterized by active ocean water circulationand desirable water quality including lowturbidity and high salinity (35-36ppt). [Figure1, sites A1-A20, blue dots].

2) Secondary swimming sites on Oahu; thiscategory of waters included sites designated forpublic swimming but considered secondarysites because waterquality is compromisedby nearby land-baseddischarges - streams orstorm drains. The watersat these sites arecharacterized bymoderate ocean watercirculation and someundesirable water qualityparameters such asincreased turbidity andlow to variable salinity(3-32ppt). [Figure 1,sites B1-B26, greendots].

3) Sites on Oahu notdesignated for swimming;this category of watersincluded harbors, canalsand other inlandwaterways, which havepoor ocean watercirculation and receivedischarges from multipleland-based sources.Though these waters arenot designated forswimming, individualswho engage in otherrecreational activities(fishing, boating) maycome into contact with them. The water qualityat these sites is classified as poor and unfit forswimming because of high turbidity, high fecalbacterial concentrations and low to variablesalinity [Figure 1, sites C1-C11, D1-D3, E1-E3].

Figure 1. Samplingsites on the islandof Oahu

Figure 2. Samplingsites on the islandof Hawaii

4) Sites on the Island of Hawaii which receivegroundwater discharge, and where past evidenceof V. vulnificus transmission has been seen[Figure 2] These sites generally have poor oceanwater circulation and variable salinity. The geologyof Hawaii, the youngest of the Hawaiian islands,features highly porous lava rock which permitsrapid and direct movement of groundwater.

Based on previousstudies done at WRRCand elsewhere, the threemost feasible andreliable culture methodsto recover andenumerate the fourpathogenic Vibrio spp.are TCBS (thiosulfate-citrate-bile salts-sucrose) media, CPC(cellobiose-polymyxinB-colistin) media, andCHROMagar Vibriomedia. These threemedia were used in Dr.Vithanage’s study. Inaddition to the microbialtesting, water sampleswere assayed forsalinity and turbidity.Biochemical assays andmolecular methodswere used to confirmthe identity of theisolated Vibrio spp.

Findings:

Significant differenceswere seen in theprevalence of

pathogenic Vibrio spp in the four different categories ofcoastal waters. A summary of results:

1. Primary swimming beaches (Oahu) arecharacterized by predominance (100%) of V.alginolyticus while V. vulnificus and V.parahaemolyticus were not recovered.

2. Secondary swimming waters (Oahu) are characterizedby predominance (100%) of V. alginolyticus, andmoderate recovery of V. vulnificus (40%) and V.parahaemolyticus (20%).

3. Non-designated swimming waters (Oahu) arecharacterized by predominance (100%) of V.alginolyticus, low to moderate recovery of V.vulnificus (<1-57%) and moderate to high recoveryof V. parahaemolyticus (40-71%).

4. Water samples obtained from the Island of Hawaii arecharacterized by predominance (89-100%) of V.alginolyticus, moderate to high recovery rates of V.vulnificus (22-100%) and moderate to high recoveryrates of V. parahaemolyticus (22-75%).

5. V. cholerae was not detected at any of the samplingsites.

Although V. cholerae was not recovered from any of the water samples, it was consistently found in raw andprimary treated sewage (but not final effluent) from three different wastewater treatment plants. This is aninteresting finding because it suggests that people are consistently shedding this species through their feces yetare most likely asymptomatic. It is also important in the sense that when there are sewage spills these bacteriaare more than likely being released in large numbers into the environment. In contrast, the other three species ofVibrio (V. vulnificus, V. parahaemolyticus, V. alginolyticus) were either not found or only sporadically foundin sewage.

Dr. Vithanage will be delivering a seminar on this subject at the upcoming WRRC seminar on Thursday, Oct.20, 2011 in Watanabe Hall room 420, on the UH Manoa campus at 3:00PM. Admission is free and all arewelcome.

Water Resources Research Center, Holmes Hall 283, University of Hawaii at Manoa

2540 Dole St. Honolulu, HI 96822 (808) 956-7847 v (808) 956-5044 f

http://www.wrrc.hawaii.edu

Vibrio vulnificus, one of the pathogenic Vibriosfound in marine waters around Hawaii.