Category Archives: Vibrio parahaemolyticus

Research – Enzymatic Inactivation of Pathogenic and Nonpathogenic Bacteria in Biofilms in Combination with Chlorine

Journal of Food Protection

This study investigated the effects of enzyme application on biofilms of bacterial isolates from a cafeteria kitchen and foodborne pathogens and the susceptibility of Salmonella biofilms to proteinase K combined with chlorine treatment. For four isolates from a cafeteria kitchen (Acinetobacter, Enterobacter, and Kocuria) and six strains of foodborne pathogens (Salmonella enterica, Staphylococcus aureus, and Vibrio parahaemolyticus), the inhibitory effect of enzymes on biofilm formation at 25°C for 24 h or the degradative efficacy of enzymes on 24-h mature biofilm at 37°C for 1 h in tryptic soy broth (TSB) was examined in a polystyrene microtiter plate. The effect of enzymes was also evaluated on a subset of these strains in 20 times diluted TSB (1/20 TSB) at 25°C. The working concentrations of five enzymes were 1 U/100 μL for α-amylase, amyloglucosidase, cellulase, and DNase and 1 milli-Anson unit/100 μL for proteinase K. In addition, 24-h mature SalmonellaTyphimurium biofilm on a stainless steel coupon was treated with proteinase K for 1 h at 25°C followed by 20 ppm of chlorine for 1 min at 25°C. The results showed that certain enzymes inhibited biofilm formation by the kitchen-originated bacteria; however, the enzymatic effect was diminished on the mature biofilms. Biofilm formation of V. parahaemolyticus was suppressed by all tested enzymes, whereas the mature biofilm was degraded by α-amylase, DNase I, and proteinase K. Proteinase K was effective in controlling Salmonella biofilms, whereas a strain-dependent variation was observed in S. aureusbiofilms. In 1/20 TSB, Enterobacter cancerogenus and Kocuria varians were more susceptible to certain enzymes during biofilm formation than those in TSB, whereas the enzymatic effect was much decreased on 24-h mature biofilms, regardless of nutrient conditions. Furthermore, synergistic inactivation of Salmonella Typhimurium in biofilms was observed in the combined treatment of proteinase K followed by chlorine. Live/Dead assays also revealed a decrease in density and loss of membrane integrity in Salmonella Typhimurium biofilms exposed to the combined treatment. Therefore, certain enzymes can control biofilms of isolates residing in a cafeteria kitchen and foodborne pathogens. This study demonstrates the potential of enzymes for the sanitation of food processing environments and of proteinase K combined with chlorine to control Salmonella biofilms on food contact surfaces.

RASFF Alerts – Vibrio cholerae and Vibrio parahaemolyticus – Frozen Shrimp

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RASFF – Vibrio cholerae and Vibrio parahaemolyticus in frozen shrimp from Vietnam in Norway

Research – Vibrio spp. from Yesso scallop (Patinopecten yessoensis) demonstrating virulence properties and antimicrobial resistance

Wiley Online Library

Abstract

We report the prevalence and characterization of Vibrio spp. isolated from marketed Yesso scallop (Patinopecten yessoensis) in Korea. A total of 30 isolates including, V. parahaemolyticus (n = 2), V. alginolyticus (n = 9), V. fluvialis (n = 7), V. diabolicus (n = 7), V. anguillarum (n = 4) and V. aestuarianus (n = 1) were isolated and identified. The phenotypic pathogenicity tests demonstrated that, 18 (60%), 21 (70%), 18 (60%), 7 (23%), 22 (73%), 21 (70%), 9 (30%), and 11 (33%) of the isolates were positive for DNase, protease, gelatinase, lipase, phospho‐lipase, amylase, slime production, and haemolysis, respectively. PCR assays revealed the prevalence of toxR, tlh, VAC, vfh, hupO, and VPI genes among the isolates with varying combinations. A close genetic affinity among V. alginolyticus and V. diabolicus strains was observed. Also the virulence genes specific to one Vibrio species were detected among other species as well. In addition, 29/30 (97%) isolates were multidrug resistant, while higher resistance rates were shown for ampicillin, colistin, vancomycin, and cephalothin. The results imply that the scallops in Korean markets harbor Vibrio spp., which are potentially virulent and multidrug resistant, thus their public health implications should not be underrated.

Practical applications

For many decades, vibrios are known for its importance in seafoodborne illnesses. Yesso scallop is the most popular and extensively cultured scallop variety in Korea. Therefore, we sought to assess the marketed fresh Yesso scallops for the prevalence and molecular characterization of Vibrio species. A total of 30 strains were isolated and identified by a series of biochemical tests, subsequent gyrB gene sequencing and phylogenetic analyses. Six Vibrio spp. were identified with V. alginolyticus as the most prevalent. Interestingly, V. alginolyticus was genetically similar to V. diabolicus. Besides, the virulence genes specific to V. alginolyticus and V. parahaemolyticus were observed in other species as well. It suggests that the detection of the species‐specific genes does not ensure the correct identification of pathogenic vibrios. Further, the occurrence of V. parahaemolyticus‐specific virulence genes in other Vibrio spp. potentially complicates the correct tracking of V. parahaemolyticus infections. In addition, 73% of these Vibrio spp. isolates showed multiple antibiotic resistance (MAR) indices higher than 0.2, which signifies their high risk of infection. Collectively, these results provide important evidence that not only the well‐known pathogenic vibrios like V. parahaemolyticus, but also other Vibrio spp. can act alike because of their similar characteristics.

Research – Long-Term Depuration of Crassostrea virginica Oysters at Different Salinities and Temperatures Changes Vibrio vulnificus Counts and Microbiological Profile

Journal of Food Protection

Previous short-duration depuration studies with the eastern oyster (Crassostrea virginica) demonstrated difficulty in achieving significant naturally incurred Vibrio vulnificus population count reductions. The present study used long-duration depuration (14 days) at controlled temperatures (10 or 22°C) and salinities (12, 16, or 20 mg/g). All depuration temperature–salinity combinations significantly reduced V. vulnificus counts, with greatest reductions seen in 12 mg/g, 10°C seawater (2.7-log CFU/g reduction) and in 20 mg/g, 22°C seawater (2.8-log reduction). Mesophilic vibrios dominated the overall microflora of freshly harvested oysters, whereas refrigerated storage selected for psychrotrophic bacteria (Pseudomonas spp., Aeromonas spp., Shewanella spp., Psychrobacter spp.) as well as did depuration at 10°C (Pseudoalteromonas spp., Shewanella spp., Vibrio spp.). Depuration at 22°C retained dominance of mesophilic vibrios, including pathogenic species, followed by Shewanella spp., Pseudoalteromonas spp., and Photobacterium spp. Although aerobic plate counts were lower in 22°C depurated oysters (5.0 log versus 6.0 log) compared with 10°C, depuration at 10°C offered greater V. vulnificus population reductions than depuration at 22°C. This advantage was only seen at 12 mg/g salinity, with no impact at 16 and 20 mg/g salinities. No depuration treatment reduced V. vulnificus counts to nondetectable levels. Use of prolonged depuration may be a helpful intervention to control V. vulnificus populations in oysters.

RASFF Alert- Vibrio parahaemolyticus – Frozen Squid

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RASFF-Vibrio parahaemolyticus in frozen squid (Loligo spp.) from India in Greece

Research – How to kill pathogens on seafood

Food Processing

Controlled release antimicrobial film makes seafood safer.

Seafood may be contaminated with bacterial pathogens, such as Vibrio and Salmonella, which can survive long-term freezing conditions. Vibrio naturally occur in marine environments and Salmonella can contaminate seafood during production or processing and both are concerns for the seafood industry.

However, a solution may be at hand. A biodegradable, edible film made with plant starch and antimicrobial compounds may control the growth of foodborne pathogens on seafood, according to a group of international researchers.

Catherine Cutter, professor of food science, Penn State, explained, “We have the ability to develop a film with antimicrobial activity that can kill foodborne pathogens on food surfaces. Given the recent outbreaks that we have seen with a number of food products, coming up with something that can be used by the industry to kill microorganisms on the surfaces of food is a noble area of research to investigate.

Vibrio and Salmonella are somewhat susceptible to freezing,” Cutter said. “So, if you treat bacterial cells with antimicrobials and then freeze them, the approach can be more lethal.”

Freezing does not kill bacteria. However, when freezing food, ice crystals can form from the water in food. The ice crystals, Cutter said, can act like “daggers” and pierce the bacterial cell wall, causing damage to the cell.

Researchers used a blend of thermoplastic starch, a biodegradable polymer made from tapioca powder and a gelatin coating containing antimicrobials known as Nisin Z and lauric arginate (LAE).

 

Hong Kong – Test results on microbiological quality of poon choi all satisfactory

CFS

 

The Centre for Food Safety (CFS) of the Food and Environmental Hygiene Department today (November 26) announced the test results of a recently completed seasonal food surveillance project on the microbiological quality of poon choi. Thirty samples were collected and all passed the tests.

A CFS spokesman said, “As poon choi is popular for gatherings during winter and there were previous cases of bacterial food poisoning associated with poon choi, the CFS has continued to conduct a seasonal food surveillance project this year to assess the microbiological quality of poon choi. A total of 30 poon choi samples were collected from different retailers (including online retailers) for testing of common food poisoning organisms including Bacillus cereus, Clostridium perfringens, Salmonella, coagulase-positive staphylococci organisms and Vibrio parahaemolyticus.”

Despite the satisfactory results of all samples tested, the spokesman reminded people to be careful when purchasing and enjoying this seasonal delicacy. He advised consumers to order poon choi from licensed and reliable shops, avoid prolonged storage of poon choi at room temperature to reduce the risk of bacteria growth, reheat poon choi thoroughly before consumption, consume cooked or reheated poon choi as soon as possible or keep the food at temperatures above 60 degrees Celsius, and stop consuming the food if it tastes or smells abnormal.

“The public should also maintain a balanced diet and avoid eating too much food with high levels of energy, sugar, salt or fat,” the spokesman said.

He also appealed to the food trade not to entertain orders beyond handling capacity. Traders are reminded to check the quality of food and ingredients when they are delivered to them. In addition, to reduce the risk of food poisoning, they should avoid preparing food too far in advance and take note of the temperature in storing, transporting and preparing food.

“All food and food ingredients should be stored at safe temperatures while perishable items should be stored at 4 degrees C or below. The cooling time of cooked food should be reduced as far as possible, for example, by dividing food into smaller portions or placing it in shallow containers. When transporting hot poon choi, it should be kept at above 60 degrees C, and for chilled poon choi, it should be kept at 4 degrees C or below,” the spokesman said.

“Traders should also provide clear advice on the proper methods of storing and reheating of poon choi to consumers so as to further reduce the risk of food poisoning due to improper handling,” he added.

The CFS will continue its surveillance of poon choi available in the market to ensure food safety and protect the health of the public.