title: Seasonal distribution of total and pathogenic Vibrio parahaemolyticus in Chesapeake Bay oysters and waters.
abstract: The objectives of this study were to investigate the seasonal distribution of total and pathogenic Vibrio parahaemolyticus in the Chesapeake Bay oysters and waters, and to determine the degree of association between V. parahaemolyticus densities and selected environmental parameters. Oyster and water samples were collected monthly from three sites in Chesapeake Bay, Maryland from November 2004 through October 2005. During collection of samples, water temperature, salinity, turbidity, dissolved oxygen, pH, chlorophyll a, and fecal coliform levels in oysters were also determined. V. parahaemolyticus levels were enumerated by a quantitative direct-plating method followed by DNA colony hybridization; presence/absence was further determined by overnight broth enrichment followed by either standard colony isolation or real-time PCR. The thermolabile hemolysin (tlh) gene and thermostable direct hemolysin (tdh) gene were targeted for detection of total and pathogenic V. parahaemolyticus, respectively, for both direct plating and enrichment. The thermostable related hemolysin (trh) gene, which is a presumptive pathogenicity marker, was targeted only for the enrichment approach. By direct plating, colonies producing tlh signals were detected in 79% of oyster samples at densities ranging from 1.5x10(1) to 6.0x10(2) CFU/g. Pathogenic V. parahaemolyticus (tdh+) was detected in 3% (level was 10 CFU/g) of oyster samples while no V. parahaemolyticus was detected in water samples. By the enrichment approach with standard colony isolation, 67% of oyster and 55% of water samples (n=33) were positive for total V. parahaemolyticus, and all samples were negative for pathogenic V. parahaemolyticus. In contrast, enrichment followed by real-time PCR detected tlh, tdh and trh in 100%, 20% and 40% of oyster and 100%, 13% and 40% of water enrichments collected from June to October 2005, respectively. V. parahaemolyticus densities in oysters varied seasonally and were found to be positively correlated with water temperature, turbidity, and dissolved oxygen.
authors.affiliation: Food Science and Technology Ph. D. Program, Department of Agriculture, Food and Resource Sciences, University of Maryland Eastern Shore, Princess Anne, Maryland 21853, United States. sparveen@umes.edu
authors.forename: Salina
authors.initials: S
authors.lastname: Parveen
authors.forename: Kumidini A
authors.initials: KA
authors.lastname: Hettiarachchi
authors.forename: John C
authors.initials: JC
authors.lastname: Bowers
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Jones
authors.forename: Mark L
authors.initials: ML
authors.lastname: Tamplin
authors.forename: Rusty
authors.initials: R
authors.lastname: McKay
authors.forename: William
authors.initials: W
authors.lastname: Beatty
authors.forename: Kathy
authors.initials: K
authors.lastname: Brohawn
authors.forename: Ligia V
authors.initials: LV
authors.lastname: Dasilva
authors.forename: Angelo
authors.initials: A
authors.lastname: Depaola
mesh_terms: D000818:Animals; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000235:genetics; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004269:DNA, Bacterial / Q000032:analysis; D005506:Food Contamination / Q000032:analysis*; D006460:Hemolysin Proteins / Q000235:genetics*; D006801:Humans; D008396:Maryland; D010125:Ostreidae / Q000382:microbiology*; D012621:Seasons; D012680:Sensitivity and Specificity; D012758:Shellfish / Q000382:microbiology*; D014736:Vibrio parahaemolyticus / Q000254:growth & development / Q000302:isolation & purification* / Q000472:pathogenicity*; D014871:Water Microbiology
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004269:DNA, Bacterial; D006460:Hemolysin Proteins; C073845:hemolysin, Vibrio; C068489:thermostable direct hemolysin