Seasonal and Geographical Differences in Total and Pathogenic Vibrio parahaemolyticus and Vibrio vulnificus Levels in Seawater and Oysters from the Delaware and Chesapeake Bays Determined Using Several Methods

Abstract

Oyster and seawater samples were collected from five sites in the Chesapeake Bay, MD, and three sites in the Delaware Bay, DE, from May–October 2016 and 2017. Abundances and detection frequencies for total and pathogenic Vibrio parahaemolyticus and Vibrio vulnificus were compared using the standard Most Probable Number-PCR (MPN-PCR) assay and a direct plating (DP) method on CHROMagar™ Vibrio for total (tlh+ ) and pathogenic (tdh+ and trh+) V. parahaemolyticus genes, and total (vvhA) and pathogenic (vcgC) genes for V. vulnificus. The Colony Overlay Procedure for Peptidases (COPP) assay was evaluated for total Vibrionaceae. DP had high false negative rates (14–77%) for most PCR targets and was deemed unsatisfactory. Logistic regression models of the COPP assay showed high concordances with MPN-PCR for tdh+ and trh+ V. parahaemolyticus and vvhA+ V. vulnificus in oysters (85.7–90.9%) and seawater (81.1–92.7%) when seawater temperature and salinity were factored into the model, suggesting that the COPP assay could potentially serve as a more rapid method to detect vibrios in oysters and seawater. Differences in total Vibrionaceae and pathogenic Vibrio abundances between state sampling sites over different collection years were contrasted for oysters and seawater by MPN-PCR. Abundances of tdh+ and trh+ V. parahaemolyticus were ∼8-fold higher in Delaware than in Maryland oysters, whereas abundances of vcgC+ V. vulnificus were nearly identical. For Delaware oysters, 93.5% were both tdh+ and trh+ compared to only 19.2% in Maryland. These results indicate that pathogenic V. parahaemolyticus was more prevalent in the Delaware Bay compared to the Chesapeake Bay. IMPORTANCE While V. parahaemolyticus and V. vulnificus cause shellfish-associated morbidity and mortality among shellfish consumers, current regulatory assays for vibrios are complex, time-consuming, labor intensive, and relatively expensive. In this study, the rapid, simple and inexpensive COPP assay was identified as a possible alternative to MPN-PCR for shellfish monitoring. This paper shows differences in total Vibrionaceae and pathogenic vibrios found in seawater and oysters from the commercially important Delaware and Chesapeake bays. Vibrio parahaemolyticus isolates from the Delaware Bay were more likely to contain commonly recognized pathogenicity genes than those from the Chesapeake Bay.

Prevalence and Abundance of Bacterial Pathogens of Concern in Shrimp, Catfish and Tilapia Obtained at Retail Stores in Maryland, USA

“…Global seafood production has been increasing dramatically during the last three decades [ 1 , 2 ]. Approximately 88% of this production was directly consumed by humans [ 1 ].…”

Examining the Relationship between Climate Change and Vibriosis in the United States: Projected Health and Economic Impacts for the 21st Century

“…It is not possible to account in our projections for future changes that may affect bacterial spread or pathogenicity and thus disease incidence rate and burden, including rates of importation and storage of live contaminated bivalve shellfish in local waters, ballast water movement, or long-distance oceanic transportation of strains into new regions. 68 Changes in variety and concentrations of Vibrio species and serotypes present in areas with vibriosis cases, some of which may be more pathogenic than others, 69 , 70 is an area of additional research.…”

Genome sequence analysis of Vibrio parahaemolyticus lytic phage vP_VpaS_VP-RY-9

“…It is commonly found in marine or freshwater animals ( sh, shrimp, and shell sh), seabed sediments, and coastal environments [3,10,11]. Its densities in the environment vary greatly with season and location [8]. As a pathogen of humans, it not only causes important economic losses to the aquaculture industry but also threatens food safety, inducing severe diarrhea and acute gastroenteritis in worldwide.…”