Differences in Abundances of Total Vibrio spp., V. vulnificus, and V. parahaemolyticus in Clams and Oysters in North Carolina

Abstract

Filter feeding shellfish can concentrate pathogenic bacteria, including Vibrio vulnificus and Vibrio parahaemolyticus, as much as 100-fold from the overlying water. These shellfish, especially clams and oysters, are often consumed raw, providing a route of entry for concentrated doses of pathogenic bacteria into the human body. The numbers of foodborne infections with these microbes are increasing, and a better understanding of the conditions that might trigger elevated concentrations of these bacteria in seafood is needed. In addition, if bacterial concentrations in water are correlated with those in shellfish, then sampling regimens could be simplified, as water samples can be more rapidly and easily obtained. After sampling of oysters and clams, either simultaneously or separately, for over 2 years, it was concluded that while Vibrio concentrations in oysters and water were related, this was not the case for levels in clams and water. When clams and oysters were collected simultaneously from the same site, the clams were found to have lower Vibrio levels than the oysters. Furthermore, the environmental parameters that were correlated with levels of Vibrio spp. in oysters and water were found to be quite different from those that were correlated with levels of Vibrio spp. in clams.IMPORTANCE This study shows that clams are a potential source of infection in North Carolina, especially for V. parahaemolyticus. These findings also highlight the need for clam-specific environmental research to develop accurate Vibrio abundance models and to broaden the ecological understanding of clam-Vibrio interactions. This is especially relevant as foodborne Vibrio infections from clams are being reported.KEYWORDS clams, ecology, food, oysters, shellfish, Vibrio A n estimated 84,000 people contract foodborne Vibrio infections each year in the United States, resulting in 500 hospitalizations and 100 deaths (1, 2). Unlike most other major foodborne bacterial pathogens, the number of cases caused by Vibrio spp. is increasing and currently is the highest since national reporting began (2, 3). While at least 12 Vibrio spp. are potentially pathogenic to humans, the two foodborne Vibrio spp. that cause the most infections and the most deaths in the United States are Vibrio parahaemolyticus and Vibrio vulnificus, respectively (2, 4).V. vulnificus is the single most fatal foodborne pathogen in the United States, and perhaps the world (4), accounting for 95% of all U.S. seafood-related deaths, with a fatality rate approaching 50% (5). Infections resulting from ingestion typically produce symptoms such as fever, chills, nausea, abdominal pain, hypotension, and the development of secondary lesions on the extremities (5, 6). V. parahaemolyticus infections are

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

“…Although pathogenic Vibrio strains are hazards for coastal systems (5,(8)(9)(10), most Vibrio strains are harmless (5). Vibrios are present in a great variety of aquatic environments from coastal areas to the deep sea (2,5), indicating that they occupy a wide range of environmental niches.…”

Inactivation ofVibriosp. in pure cultures and mussel homogenates using high hydrostatic pressure

“…in mussel homogenates (completely inactivated to nondetectable level) was obtained at a treatment of 350 and 450 MPa for 1 and 3 min (determined on both thiosulphate citrate bile salt sucrose (TCBS) and TSA agar), except for V. parahaemolyticus with a 4Á4 log reduction by a treatment of 350 MPa for 1 min (determined on TSA agar). At harvest, the density of Vibrio in shellfish is usually less than 10 3 CFU per gram but can exceed 10 3 CFU per gram during summer (Froelich et al 2017). However, under improper postharvest conditions, Vibrio can rapidly multiply to reach the density of 10 5 -10 6 cells per gram (Cook 1994;Gooch et al 2002).…”

Managing the risk of Vibrio parahaemolyticus infections associated with oyster consumption: A review

“…Consequently, they may differ in their preference of consuming wild‐caught or aquacultured oysters. However, studies on comparisons between the risk of V. parahaemolyticus infection resulting from the consumption of wild‐caught oysters and aquacultured oysters are limited (Froelich, Phippen, Fowler, Noble, & Oliver, 2017). Nevertheless, studies have shown that the culturing method affects the concentration of V. parahaemolyticus in oysters (Cole, Supan, Ramirez, & Johnson, 2015; Feinman, Farah, Bauer, & Bowen, 2018).…”

“…Froelich et al. (2017) performed a study in the same location, North Carolina coast, and reported that SST was strongly correlated with the abundance of V. parahaemolyticus in oysters. A recent study by Hartwick et al.…”

“…However, the result of that study may be affected by the sampling location and bivalve species (Lopez‐Joven et al., 2015). This is important because the concentration of V. parahaemolyticus can differ significantly between bivalve species, even if they are collected from the same location at the same period of time (Froelich et al., 2017). Understanding the influence of environmental condition on the concentration and distribution of V. parahaemolyticus that carry virulence strains in oysters will allow a better prediction of food safety risk associated with the consumption of oysters (Zimmerman et al., 2007).…”