Investigation into Pathogenic Vibio parahaemolyticus dynamics and Virulence determinants from Hawaiian Waters
Investigation into Pathogenic Vibio parahaemolyticus dynamics and Virulence determinants from Hawaiian Waters
Date
2008
Authors
Marchant, Brett
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Advisor
Steward, Grieg
Department
Oceanography
Global Environmental Science
Global Environmental Science
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Abstract
The pathogenic gram-negative halophilic bacterium, Vibrio parahaemolyticus, is
a water-borne human pathogen indigenous to coastal marine and estuarine environments.
When introduced to a human host, either by the consumption of raw or undercooked
shellfish, or by exposure to an open wound, the pathogen can cause gastroenteritis, tissue
infection, and, in some cases, septicemia. The risk of human infection is expected to be
directly associated to the abundance of pathogenic V. parahaemolyticus. To evaluate how
environmental conditions may influence the abundance of this pathogen I investigated the
spatial, temporal, and environmental prevalence of Vibrio parahaemolyticus in the Ala
Wai Canal and surrounding waters of Honolulu, Hawai’i. Strains of V. parahaemolyticus
were isolated on selective media along an environmental gradient and at frequencies
ranging from months to hours. Putative V. parahaemolyticus isolates were identified
using chromogenic media. Their identities were later confirmed using molecular
methods, and they were analyzed for the presence of known virulence-associated genes.
The species-specific(tlh) gene was found in 79% of the putative V. parahaemolyticus
isolates, but none of these were positive for a virulence-associated gene (tdh). There was
a positive correlation between total V. parahaemolyticus abundance and salinity, but only
in the range from 2.5-19 ppt. No significant correlation was found between temperature
and V. parahaemolyticus abundance. Highest V. parahaemolyticus densities were usually
found at the head of the canal and at the mouths of the two streams feeding into the canal
(stations 1-6, 9 and 12). This information may prove useful for modeling pathogen
dynamics in tropical coastal environments.
Description
The pathogenic gram-negative halophilic bacterium, Vibrio parahaemolyticus, is
a water-borne human pathogen indigenous to coastal marine and estuarine environments.
When introduced to a human host, either by the consumption of raw or undercooked
shellfish, or by exposure to an open wound, the pathogen can cause gastroenteritis, tissue
infection, and, in some cases, septicemia. The risk of human infection is expected to be
directly associated to the abundance of pathogenic V. parahaemolyticus. To evaluate how
environmental conditions may influence the abundance of this pathogen I investigated the
spatial, temporal, and environmental prevalence of Vibrio parahaemolyticus in the Ala
Wai Canal and surrounding waters of Honolulu, Hawai’i. Strains of V. parahaemolyticus
were isolated on selective media along an environmental gradient and at frequencies
ranging from months to hours. Putative V. parahaemolyticus isolates were identified
using chromogenic media. Their identities were later confirmed using molecular
methods, and they were analyzed for the presence of known virulence-associated genes.
The species-specific(tlh) gene was found in 79% of the putative V. parahaemolyticus
isolates, but none of these were positive for a virulence-associated gene (tdh). There was
a positive correlation between total V. parahaemolyticus abundance and salinity, but only
in the range from 2.5-19 ppt. No significant correlation was found between temperature
and V. parahaemolyticus abundance. Highest V. parahaemolyticus densities were usually
found at the head of the canal and at the mouths of the two streams feeding into the canal
(stations 1-6, 9 and 12). This information may prove useful for modeling pathogen
dynamics in tropical coastal environments.
Keywords
microbiology,
pathogen,
water quality
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90 pages
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