Application of Chitosan Microparticles for Reduction of Vibrio Species in Seawater and Live Oysters (Crassostrea virginica)

Abstract

bHuman Vibrio infections associated with consumption of raw shellfish greatly impact the seafood industry. Vibrio cholerae-related disease is occasionally attributed to seafood, but V. vulnificus and V. parahaemolyticus are the primary targets of postharvest processing (PHP) efforts in the United States, as they pose the greatest threat to the industry. Most successful PHP treatments for Vibrio reduction also kill the molluscs and are not suitable for the lucrative half-shell market, while nonlethal practices are generally less effective. Therefore, novel intervention strategies for Vibrio reduction are needed for live oyster products. Chitosan is a bioactive derivative of chitin that is generally recognized as safe as a food additive by the FDA, and chitosan microparticles (CMs) were investigated in the present study as a potential PHP treatment for live oyster applications. Treatment of broth cultures with 0.5% (wt/vol) CMs resulted in growth cessation of V. cholerae, V. vulnificus, and V. parahaemolyticus, reducing culturable levels to nondetectable amounts after 3 h in three independent experiments. Furthermore, a similar treatment in artificial seawater at 4, 25, and 37°C reduced V. vulnificus levels by ca. 7 log CFU/ml after 24 h of exposure, but 48 h of exposure and elevated temperature were required to achieve similar results for V. parahaemolyticus and V. cholerae. Live oysters that either were artificially inoculated or contained natural populations of V. vulnificus and V. parahaemolyticus showed significant and consistent reductions following CM treatment (5%) compared to the amounts in the untreated controls. Thus, the results strongly support the promising potential for the application of CMs as a PHP treatment to reduce Vibrio spp. in intact live oysters.V ibrio species cause a significant proportion of human infections associated with consumption of raw or undercooked shellfish, particularly raw oysters (1). The primary pathogens in the United States are Vibrio vulnificus and V. parahaemolyticus; however, in 2011 the first U.S. outbreak of cholera in recent history was attributed to the consumption of oysters contaminated with V. cholerae O75 (2). Unlike other foodborne pathogens associated with seafood, Vibrio spp. occur naturally in estuarine environments, and their abundance is seasonal (3, 4). During warmer months (when the water temperature is Ͼ20°C), nearly all oysters harvested from U.S. Gulf Coast waters harbor V. vulnificus and/or V. parahaemolyticus, with the highest densities periodically exceeding 10 4 most probable number (MPN)/g (5). Despite extensive efforts employing hazard analysis and critical control point approaches and improved sanitation by the seafood industry, the incidence of seafood-associated cases continues to escalate, particularly during summer months, perhaps as a consequence of increasing global water temperatures (6). Annual reports of the incidence of Vibrio-related disease per 100,000 population increased from 0.09 to 0.28 in the Cholera and Other Vibrio Illness ...

Application of chitosan microparticles for mitigation of Salmonella in agricultural water

“…Prior reports also found CM activity was similarly temperature‐ (Fang et al . ) and pH‐dependent (Jeon et al . ).…”

“…For example, CM treatment significantly decreased or eliminated survival of Vibrio species in seawater (pH 7·4), as well as in live oysters (Fang et al . ). CM reduced shedding of pathogenic Escherichia coli O157:H7 for infected cattle (Jeong et al .…”

Antimicrobial activities of high molecular weight water‐soluble chitosans against selected gram‐negative and gram‐positive foodborne pathogens

“…Fang et al . () evaluated anti‐vibrio activity of 0.5% w/v chitosan microparticles (prepared in AC) against V. cholerae, V. vulnificus and V. parahaemolyticus in broth cultures. They reported growth cessation of V. cholerae , V. vulnificus and V. parahaemolyticus , reducing culturable levels to a non‐detectable level (<10 CFU mL −1 ) after 3 h post‐treatment.…”

“…For instance, Jung et al (2010) reported that 0.05% acid (AC)-soluble chitosan with 99% DD completely inhibited V. vulnificus and V. parahaemolyticus after 24 h at 37°C. Fang et al (2015) evaluated anti-vibrio activity of 0.5% w/v chitosan microparticles (prepared in AC) against V. cholerae, V. vulnificus and V. parahaemolyticus in broth cultures. They reported growth cessation of V. cholerae, V. vulnificus and V. parahaemolyticus, reducing culturable levels to a non-detectable level (<10 CFU mL À1 ) after 3 h post-treatment.…”

Challenges and opportunities related to the use of chitosan as a food preservative

“…CN/CM were reported to be effective food preservatives (Fang et al . ; Pilon et al . ; Chouljenko et al .…”