title: Seasonal abundance of total and pathogenic Vibrio parahaemolyticus isolated from American oysters harvested in the Mandinga Lagoon System, Veracruz, Mexico: implications for food safety.
abstract: The abundance of total and pathogenic Vibrio parahaemolyticus (Vp) strains in American oysters (Crassostrea virginica) harvested in two different harvest sites from the Mandinga lagoon System was evaluated monthly for 1 year (January through December 2012). Frequencies of species-specific genes and pathogenic genes exhibited a seasonal distribution. The annual occurrence of Vp with the species-specific tlh gene (tlh(+)) was significantly higher during the winter windy season (32.50%) and spring dry season (15.0%), with the highest densities observed during spring dry season at 283.50 most probable number (MPN)/g (lagoon bank A, near human settlements), indicating the highest risk of infection during warmer months. Pathogenic Vp tlh(+)/tdh(+) frequency was significantly higher during the winter windy and the spring dry seasons at 22.50 and 10.00%, respectively, with highest densities of 16.22 and 41.05 MPN/g (bank A), respectively. The tlh/trh and tdh/trh gene combinations were also found in Vp isolates during the spring dry season at 1.25 and 1.3%, respectively, with densities of 1.79 and 0.4 MPN/g (bank A), respectively. The orf8 genes were detected during the winter windy season (1.25%) with highest densities of 5.96 MPN/g (bank A) and 3.21 MPN/g (bank B, near mangrove islands and a heron nesting area). Densities of Vp tdh(+) were correlated (R(2) = 0.245, P < 0.015) with those of Vp orf8(+). The seasonal dynamics of Vp harboring pathogenic genes varied with seasonal changes, with very high proportions of Vp tdh(+) and Vp orf8(+) isolates in the winter windy season at 46.2 and 17.0%, respectively, which suggests that environmental factors may differentially affect the abundance of pathogenic subpopulations. Although all densities of total Vp (Vp tlh(+)) were lower than 10(4) MPN/g, thus complying with Mexican regulations, the presence of pathogenic strains is a public health concern. Our results suggest that total Vp densities may not be appropriate for assessing oyster contamination and predicting the risk of infection. Evaluation of the presence of pathogenic strains would be a better approach to protecting public health.
authors.affiliation: Faculty of Veterinary Medicine, Universidad Veracruzana, Avenida Miguel Ángel de Quevedo s/n esquina Yáñez, Colonia Unidad Veracruzana, Veracruz, Veracruz, México 91710.
authors.forename: Argel
authors.initials: A
authors.lastname: Flores-Primo
authors.forename: Violeta
authors.initials: V
authors.lastname: Pardío-Sedas
authors.forename: Leonardo
authors.initials: L
authors.lastname: Lizárraga-Partida
authors.forename: Karla
authors.initials: K
authors.lastname: López-Hernández
authors.forename: Roxana
authors.initials: R
authors.lastname: Uscanga-Serrano
authors.forename: Reyna
authors.initials: R
authors.lastname: Flores-Hernández
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D049896:Crassostrea / Q000254:growth & development / Q000382:microbiology*; D005506:Food Contamination / Q000032:analysis*; D059022:Food Safety; D006801:Humans; D008800:Mexico; D012621:Seasons; D012758:Shellfish / Q000382:microbiology*; D014481:United States; D014736:Vibrio parahaemolyticus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D001426:Bacterial Proteins