Impact of seafood regulations for Vibrio parahaemolyticus infection and verification by analyses of seafood contamination and infection

Vibriosis in South Asia: A systematic review and meta-analysis

OBJECTIVES

South Asia remains home to foodborne diseases caused by the Vibrio species. We aimed to compile and update information on the epidemiology of vibriosis in South Asia.

METHODS

For this systematic review and meta-analysis, we searched PubMed, Web of Science, EMBASE, and Google Scholar for studies related to vibriosis in South Asia published up to May 2023. A random-effects meta-analysis was used to estimate the pooled isolation rate of non-cholera-causing Vibrio species.

RESULTS

In total, 38 studies were included. Seven of these were case reports and 22 were included in the meta-analysis. The reported vibriosis cases were caused by non-O1/non-O139 V. cholerae, V. parahaemolyticus, V. fluvialis, and V. vulnificus. The overall pooled isolation rate was 4.0% (95% confidence interval [CI] 3.0-5.0%) in patients with diarrhea. Heterogeneity was high (I2 = 98.0%). The isolation rate of non-O1/non-O139 V. cholerae, V. parahaemolyticus, and V. fluvialis were 9.0 (95% CI 7.0-10.0%), 1.0 (95% CI 1.0-2.0%), and 2.0 (95% CI: 1.0-3.0%), respectively. Regarding V. parahaemolyticus, O3:K6 was the most frequently isolated serotype. Cases peaked during summer. Several studies reported antibiotic-resistant strains and those harboring extended-spectrum beta-lactamases genes.

CONCLUSIONS

This study demonstrates a high burden of infections caused by non-cholera-causing Vibrio species in South Asia.

Prevalence, virulence characteristics, and antimicrobial resistance of Vibrio parahaemolyticus isolates from raw seafood in a province in Northern Thailand

Vibrio parahaemolyticus (V. parahaemolyticus) is commonly found in seawater and seafood products, but evidence is limited of its presence in seafood marketed in locations very distant from coastal sources. This study determined the prevalence and characterization of V. parahaemolyticus in seafood from markets in landlocked Phayao province, Northern Thailand. Among 120 samples, 26 (21.7%) were positive for V. parahaemolyticus, being highest in shrimp (43.3%), followed by shellfish (36.7%), and squid (6.7%), but was not found in fish. V. parahaemolyticus comprised 33 isolates that were non-pathogenic and non-pandemic. Almost all isolates from shrimp and shellfish samples were positive for T3SS1. Only five isolates (15.2%) showed two antimicrobial resistance patterns, namely, kanamycin-streptomycin (1) carrying sul2 and ampicillin-kanamycin-streptomycin (4) that carried tetA (2), tetA-sul2 (1), as well as one negative. Antimicrobial susceptible V. parahaemolyticus isolates possessing tetA (67.9%) and sul2 (3.5%) were also found. Six isolates positive for integron class 1 and/or class 2 were detected in 4 antimicrobial susceptible and 2 resistant isolates. While pathogenic V. parahaemolyticus was not detected, contamination of antimicrobial resistance V. parahaemolyticus in seafood in locations distant from coastal areas requires ongoing monitoring to improve food safety in the seafood supply chain.

End-point rapid detection of total and pathogenic Vibrio parahaemolyticus (tdh+ and/or trh1+ and/or trh2+) in raw seafood using a colorimetric loop-mediated isothermal amplification-xylenol orange technique

Background

Vibrio parahaemolyticus is the leading cause of bacterial seafood-borne gastroenteritis in humans worldwide. To ensure seafood safety and to minimize the occurrence of seafood-borne diseases, early detection of total V. parahaemolyticus (pathogenic and non-pathogenic strains) and pathogenic V. parahaemolyticus (tdh+ and/or trh1+ and/or trh2+) is required. This study further improved a loop-mediated isothermal amplification (LAMP) assay using xylenol orange (XO), a pH sensitive dye, to transform conventional LAMP into a one-step colorimetric assay giving visible results to the naked eye. LAMP-XO targeted rpoD for species specificity and tdh, trh1, and trh2 for pathogenic strains. Multiple hybrid inner primers (MHP) of LAMP primers for rpoD detection to complement the main primer set previously reported were designed by our group to maximize sensitivity and speed.

Methods

Following the standard LAMP protocol, LAMP reaction temperature for rpoD, tdh, trh1, and trh2 detection was first determined using a turbidimeter. The acquired optimal temperature was subjected to optimize six parameters including dNTP mix, betaine, MgSO4, Bst 2.0 WarmStart DNA polymerase, reaction time and XO dye. The last parameter was done using a heat block. The color change of the LAMP-XO result from purple (negative) to yellow (positive) was monitored visually. The detection limits (DLs) of LAMP-XO using a 10-fold serial dilution of gDNA and spiked seafood samples were determined and compared with standard LAMP, PCR, and quantitative PCR (qPCR) assays. Subsequently, the LAMP-XO assay was validated with 102 raw seafood samples and the results were compared with PCR and qPCR assays.

Results

Under optimal conditions (65 °C for 75 min), rpoD-LAMP-XO and tdh-LAMP-XO showed detection sensitivity at 102 copies of gDNA/reaction, or 10 folds greater than trh1-LAMP-XO and trh2-LAMP-XO. This level of sensitivity was similar to that of standard LAMP, comparable to that of the gold standard qPCR, and 10-100 times higher than that of PCR. In spiked samples, rpoD-LAMP-XO, tdh-LAMP-XO, and trh2-LAMP-XO could detect V. parahaemolyticus at 1 CFU/2.5 g spiked shrimp. Of 102 seafood samples, LAMP-XO was significantly more sensitive than PCR (P < 0.05) for tdh and trh2 detection and not significantly different from qPCR for all genes determined. The reliability of tdh-LAMP-XO and trh2-LAMP-XO to detect pathogenic V. parahaemolyticus was at 94.4% and 100%, respectively.

Conclusions

To detect total and pathogenic V. parahaemolyticus, at least rpoD-LAMP-XO and trh2-LAMP-XO should be used, as both showed 100% sensitivity, specificity, and accuracy. With short turnaround time, ease, and reliability, LAMP-XO serves as a better alternative to PCR and qPCR for routine detection of V. parahaemolyticus in seafood. The concept of using a one-step LAMP-XO and MHP-LAMP to enhance efficiency of diagnostic performance of LAMP-based assays can be generally applied for detecting any gene of interest.

Ultrasound-assisted blue light killing Vibrio parahaemolyticus to improve salmon preservation

Vibrio parahaemolyticus is a typical marine bacterium, which often contaminates seafood and poses a health risk to consumers. Some non-thermal sterilization technologies, such as ultrasonic field (UF) and blue light (BL) irradiation, have been widely used in clinical practice due to their efficiency, safety, and avoidance of drug resistance, but their application in food preservation has not been extensively studied. This study aims to investigate the effect of BL on V. parahaemolyticus in culture media and in ready-to-eat fresh salmon, and to evaluate the killing effectiveness of the UF combined with BL treatment on V. parahaemolyticus. The results showed that BL irradiation at 216 J/cm2 was effective in causing cell death (close to 100%), cell shrinkage and reactive oxygen species (ROS) burst in V. parahaemolyticus. Application of imidazole (IMZ), an inhibitor of ROS generation, attenuated the cell death induced by BL, indicating that ROS were involved in the bactericidal effects of BL on V. parahaemolyticus. Furthermore, UF for 15 min enhanced the bactericidal effect of BL at 216 J/cm2 on V. parahaemolyticus, with the bactericidal rate of 98.81%. In addition, BL sterilization did not affect the color and quality of salmon, and the additive UF treatment for 15 min did not significant impact on the color of salmon. These results suggest that BL or UF combined with BL treatment has potential for salmon preservation, however, it is crucial to strictly control the intensity of BL and the duration of UF treatment to prevent reducing the freshness and brightness of salmon.

Incidence, genetic diversity, and antimicrobial resistance profiles of Vibrio parahaemolyticus in seafood in Bangkok and eastern Thailand

Background

Emergence of Vibrio parahaemolyticus pandemic strain O3:K6 was first documented in 1996. Since then it has been accounted for large outbreaks of diarrhea globally. In Thailand, prior studies on pandemic and non-pandemic V. parahaemolyticus had mostly been done in the south. The incidence and molecular characterization of pandemic and non-pandemic strains in other parts of Thailand have not been fully characterized. This study examined the incidence of V. parahaemolyticus in seafood samples purchased in Bangkok and collected in eastern Thailand and characterized V. parahaemolyticus isolates. Potential virulence genes, VPaI-7, T3SS2, and biofilm were examined. Antimicrobial resistance (AMR) profiles and AMR genes (ARGs) were determined.

Methods

V. parahaemolyticus was isolated from 190 marketed and farmed seafood samples by a culture method and confirmed by polymerase chain reaction (PCR). The incidence of pandemic and non-pandemic V. parahaemolyticus and VPaI-7, T3SS2, and biofilm genes was examined by PCR. AMR profiles were verified by a broth microdilution technique. The presence of ARGs was verified by genome analysis. V. parahaemolyticus characterization was done by multilocus sequence typing (MLST). A phylogenomic tree was built from nucleotide sequences by UBCG2.0 and RAxML softwares.

Results

All 50 V. parahaemolyticus isolates including 21 pathogenic and 29 non-pathogenic strains from 190 samples had the toxRS/old sequence, indicating non-pandemic strains. All isolates had biofilm genes (VP0950, VP0952, and VP0962). None carried T3SS2 genes (VP1346 and VP1367), while VPaI-7 gene (VP1321) was seen in two isolates. Antimicrobial susceptibility profiles obtained from 36 V. parahaemolyticus isolates revealed high frequency of resistance to colistin (100%, 36/36) and ampicillin (83%, 30/36), but susceptibility to amoxicillin/clavulanic acid and piperacillin/tazobactam (100%, 36/36). Multidrug resistance (MDR) was seen in 11 isolates (31%, 11/36). Genome analysis revealed ARGs including blaCARB (100%, 36/36), tet(34) (83%, 30/36), tet(35) (42%, 15/36), qnrC (6%, 2/36), dfrA6 (3%, 1/36), and blaCTX-M-55 (3%, 1/36). Phylogenomic and MLST analyses classified 36 V. parahaemolyticus isolates into 5 clades, with 12 known and 13 novel sequence types (STs), suggesting high genetic variation among the isolates.

Conclusions

Although none V. parahaemolyticus strains isolated from seafood samples purchased in Bangkok and collected in eastern Thailand were pandemic strains, around one third of isolates were MDR V. parahaemolyticus strains. The presence of resistance genes of the first-line antibiotics for V. parahaemolyticus infection raises a major concern for clinical treatment outcome since these resistance genes could be highly expressed under suitable circumstances.

Evaluating the Spatial Risk of Bacterial Foodborne Diseases Using Vulnerability Assessment and Geographically Weighted Logistic Regression

Foodborne diseases are an increasing concern to public health; climate and socioeconomic factors influence bacterial foodborne disease outbreaks. We developed an “exposure–sensitivity–adaptability” vulnerability assessment framework to explore the spatial characteristics of multiple climatic and socioeconomic environments, and analyzed the risk of foodborne disease outbreaks in different vulnerable environments of Zhejiang Province, China. Global logistic regression (GLR) and geographically weighted logistic regression (GWLR) models were combined to quantify the influence of selected variables on regional bacterial foodborne diseases and evaluate the potential risk. GLR results suggested that temperature, total precipitation, road density, construction area proportions, and gross domestic product (GDP) were positively correlated with foodborne diseases. GWLR results indicated that the strength and significance of these relationships varied locally, and the predicted risk map revealed that the risk of foodborne diseases caused by Vibrio parahaemolyticus was higher in urban areas (60.6%) than rural areas (20.1%). Finally, distance from the coastline was negatively correlated with predicted regional risks. This study provides a spatial perspective for the relevant departments to prevent and control foodborne diseases.

A fully integrated hand-powered centrifugal microfluidic platform for ultra-simple and non-instrumental nucleic acid detection

Hand-powered centrifugal microfluidics combined with isothermal nucleic acid amplification testing (NAAT) have been one of the most promising rapid detection platforms in resource-limited settings. However, current hand-powered centrifuges still suffer from customized instrument-based operation and low rotation rate; and most isothermal NAAT were conducted with complicated reaction systems for DNA detection and required an additional step for RNA detection. Herein, we built a fully hand-powered centrifugal miniaturized NAAT platform inspired by buzzer toys, which embedded sample preparation, strand exchange amplification (SEA) and visual fluorescence detection together. The centrifugal disc was easily fabricated, and operated the mixing in 1 min by simply dragging the looped rope through it with a mean input force of 16.5 N, enabling its rotation rate reach 5000 rpm. In addition, SEA was an ultra-simple one-step DNA or RNA detection method initiated by Bst DNA polymerase and a pair of primers, and thus we took all its merits and integrate it into microfluidic systems firstly. Furthermore, taking Vibrio parahemolyticus as an example, the microfluidic platform achieved DNA or RNA detection within 1 h; and the detection limit of the microchip for artificially spiked oysters was 10³ CFU/g without cumbersome sample preparation, and reached to 10⁰ CFU/g after enrichment. Therefore, we provided an ultra-simple and non-instrumental microfluidic platform powered merely by hands, performing general potential in sample-to-answer NAAT for versatile pathogens in remote regions.

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

Vibrio parahaemolyticus is a Gram-negative bacterium that is naturally present in the marine environment. Oysters, which are water filter feeders, may accumulate this pathogen in their soft tissues, thus increasing the risk of V. parahaemolyticus infection among people who consume oysters. In this review, factors affecting V. parahaemolyticus accumulation in oysters, the route of the pathogen from primary production to consumption, and the potential effects of climate change were discussed. In addition, intervention strategies for reducing accumulation of V. parahaemolyticus in oysters were presented. A literature review revealed the following information relevant to the present study: (a) managing the safety of oysters (for human consumption) from primary production to consumption remains a challenge, (b) there are multiple factors that influence the concentration of V. parahaemolyticus in oysters from primary production to consumption, (c) climate change could possibly affect the safety of oysters, both directly and indirectly, placing public health at risk, (d) many intervention strategies have been developed to control and/or reduce the concentration of V. parahaemolyticus in oysters to acceptable levels, but most of them are mainly focused on the downstream steps of the oyster supply chain, and (c) although available regulation and/or guidelines governing the safety of oyster consumption are mostly available in developed countries, limited food safety information is available in developing countries. The information provided in this review may serve as an early warning for managing the future effects of climate change on the safety of oyster consumption.

Development of a monoclonal antibody for specific detection of Vibrio parahaemolyticus and analysis of its antigen

Vibrio parahaemolyticus is a major foodborne pathogen worldwide. Contamination of V. parahaemolyticus in foods must be detected as quickly as possible because raw seafood, a major source of V. parahaemolyticus infection, is shipped immediately after production due to its short expiration date. In this study, we generated monoclonal antibodies (mAbs) against V. parahaemolyticus to develop a rapid and specific detection assay. Obtained mAbs were categorized into four groups according to their specificity. Of the groups, Group 1 (mAb VP7, VP11, and VP24) reacted to O1-O12 of V. parahaemolyticus without cross-reaction with human pathogenic Vibrio spp. (V. alginolyticus, V. cholerae, V. fluvialis, V. furnissii, V. mimicus, and V. vulnificus). We developed an immunochromatographic (IC) strip for the rapid detection of V. parahaemolyticus in the field using VP7 as a membrane-immobilized antibody and VP24 as a colloidal gold-conjugated antibody. The IC strip detected any and all serogroups (O1 to O12) or isolates (clinical, food, and environmental strains) of V. parahaemolyticus, regardless of the presence of virulence factors thermostable direct hemolysin (TDH) or TDH-related hemolysin (TRH). It did not cross-react with any other non-V. parahaemolyticus strains tested. To elucidate the target of the IC strip, we analyzed the antigen recognized by these mAbs. Group 1 mAbs showed two specific bands at molecular masses of approximately 11 and 16 kDa by western blotting analysis. Nano liquid chromatography mass spectrometry (LC-MS)/MS analysis revealed that the candidate antigen recognized by these mAbs was outer membrane (OM) lipoprotein Q87G48. We verified that mAb VP7 detected His-tagged OM lipoprotein synthesized by reconstituted cell-free protein synthesis reagent. Reactivity to an N-terminus deletion form and protease digestion form of the OM lipoprotein showed that the extent of epitope recognized by VP mAbs was 22nd-41st amino acids (AAs) from N-terminus of the OM lipoprotein, with the sequence "²²SDDAATANAAKLDEL³⁶." This region was also confirmed to be a V. parahaemolyticus-specific sequence by comparing putative orthologs of OM lipoprotein among Vibrio spp. The C-terminus deletion form (1st-39th AAs) including the sequence primarily recognized by VP mAbs (22nd-36th AAs) showed poor reactivity, indicating that the sequence after 40 residues of OM lipoprotein is also important for recognition by VP mAbs and VP mAbs recognize a conformational epitope. Bioinformatics research demonstrated that the OM lipoprotein is an ortholog of the lpp protein conserved throughout many bacteria. Lpp is an abundant and constitutively expressed protein and exists on the bacterial surface, suggesting it may be a good target for detection of V. parahaemolyticus.

Analysis of Triphenylmethane Dye Residues and their Leuco-Forms in Frozen Fish by LC-MS/MS, Fish Microbial Quality, and Effect of Immersion in Whole Milk on Dye Removal

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was validated and used to quantify crystal violet (CV), leucocrystal violet (LCV), malachite green (MG), leucomalachite green (LMG), and brilliant green (BG) residues in frozen fish (121 samples) from various countries, in order to detect the use of prohibited antibiotic dyes in fish for human consumption. The microbial quality of the fish was also assessed along with the effectiveness of a simple treatment with whole fat milk to reduce the levels of CV and LCV contamination. CV and LCV were the only two residues detected. They were found in farmed Pangasius (0.362 to 41.34 μg/kg and 0.178 to 10.58 μg/kg, respectively) and Tilapia (1.24 to 9.48 μg/kg and 1.29 to 2.81 μg/kg). Based on aerobic plate count (APC), 74%, 59%, and 55% of the samples of Tilapia fillets (from China) and Pangasius fillets (United Arab Emirates and Vietnam), and 100% and 50% of the skin samples of Hake (Argentina and U.S.A.) were of unacceptable microbial quality (APC > 10⁷ cfu/g). Human pathogens, namely Escherichia coli, Staphylococcus aureus, and Vibrio spp., were detected in most fish. A significant reduction in CV and LCV concentrations by more than a third was achieved after immersing Pangasius and Tilapia fillets in whole fat milk for 120 minutes. These findings support the necessity of regular inspections and monitoring of CV and other antibiotic dye residues in fish, along with routine assessments of fish microbial quality, in order to protect public health. PRACTICAL APPLICATION: The described LC-MS/MS method can be used to rapidly and simultaneously quantify antibiotic dye residues in frozen fish. CV and LCV were detected in farmed Pangasius and Tilapia fillets and their concentrations was reduced by more than one third after immersing the fillets in whole milk for 120 min, a treatment which is not intended to replace safe fish farming practices upstream to artificially lower the level of banned dyes in fish. The findings support the necessity of regular inspections and monitoring of CV and other antibiotic dye residues in fish, along with assessments of fish microbial quality, to protect public health.

Vibrio Parahaemolyticus: A Review on Distribution, Pathogenesis, Virulence Determinants and Epidemiology

Vibrio parahaemolyticus is a Gram-negative, halophilic bacterium isolated from marine environments globally. After the consumption of contaminated seafood, V. parahaemolyticus causes acute gastroenteritis. To initiate infection, a wide range of virulence factors are required. A complex group of genes is known to participate in the pathogenicity of V. parahaemolyticus; however, to understand the full mechanism of infection, extensive research is yet required. V. parahaemolyticus has become the leading cause of seafood-related gastroenteritis in Japan, the United States and several other parts of the world. In addition, outbreaks caused by the pandemic clone of this organism are escalating and spreading universally. To minimize the risk of V. parahaemolyticus infection and warrant the safety of seafood, collaboration between governments and scientists is required. We herein provide an updated review of the pathogenicity determinants and distribution of V. parahaemolyticus to deliver a better understanding of the significance of V. parahaemolyticus and its host-pathogen interactions.

Emerging Seafood Preservation Techniques to Extend Freshness and Minimize Vibrio Contamination

Globally, the popularity of seafood consumption is increasing exponentially. To meet the demands of a growing market, the seafood industry has increasingly been innovating ways to keep their products fresh and safe while increasing production. Marine environments harbor several species of indigenous microorganisms, some of which, including Vibrio spp., may be harmful to humans, and all of which are part of the natural microbiota of the seafood. After harvest, seafood products are often shipped over large geographic distances, sometimes for prolonged periods, during which the food must stay fresh and pathogen proliferation must be minimized. Upon arrival there is often a strong desire, arising from both culinary and nutritional considerations, to consume seafood products raw, or minimally cooked. This supply chain along with popular preferences have increased challenges for the seafood industry. This has resulted in a desire to develop methodologies that reduce pathogenic and spoilage organisms in seafood items to comply with regulations and result in minimal changes to the taste, texture, and nutritional content of the final product. This mini-review discusses and compares several emerging technologies, such as treatment with plant derived natural compounds, phage lysis, high-pressure processing, and irradiation for their ability to control pathogenic vibrios, limit the growth of spoilage organisms, and keep the desired organoleptic properties of the seafood product intact.

The extended regulatory networks of SXT/R391 integrative and conjugative elements and IncA/C conjugative plasmids

Nowadays, healthcare systems are challenged by a major worldwide drug resistance crisis caused by the massive and rapid dissemination of antibiotic resistance genes and associated emergence of multidrug resistant pathogenic bacteria, in both clinical and environmental settings. Conjugation is the main driving force of gene transfer among microorganisms. This mechanism of horizontal gene transfer mediates the translocation of large DNA fragments between two bacterial cells in direct contact. Integrative and conjugative elements (ICEs) of the SXT/R391 family (SRIs) and IncA/C conjugative plasmids (ACPs) are responsible for the dissemination of a broad spectrum of antibiotic resistance genes among diverse species of Enterobacteriaceae and Vibrionaceae. The biology, diversity, prevalence and distribution of these two families of conjugative elements have been the subject of extensive studies for the past 15 years. Recently, the transcriptional regulators that govern their dissemination through the expression of ICE- or plasmid-encoded transfer genes have been described. Unrelated repressors control the activation of conjugation by preventing the expression of two related master activator complexes in both types of elements, i.e., SetCD in SXT/R391 ICEs and AcaCD in IncA/C plasmids. Finally, in addition to activating ICE- or plasmid-borne genes, these master activators have been shown to specifically activate phylogenetically unrelated mobilizable genomic islands (MGIs) that also disseminate antibiotic resistance genes and other adaptive traits among a plethora of pathogens such as Vibrio cholerae and Salmonella enterica.

Risk Factors for Vibrio parahaemolyticus Infection in a Southern Coastal Region of China

OBJECTIVES

The objectives of the study were to identify dietary and medical risk factors for Vibrio parahaemolyticus (VP) infection in the coastal city Shenzhen in China.

METHODS

In April-October 2012, we conducted a case-control study in two hospitals in Shenzhen, China. Laboratory-confirmed VP cases (N = 83) were matched on age, sex, and other social factors to healthy controls (N = 249). Subjects were interviewed using a questionnaire on medical history; contact with seawater; clinical symptoms and outcome; travel history over the past week; and dietary history 3 days prior to onset. Laboratory tests were used to culture, serotype, and genotype VP strains. We used logistic regression to calculate the odds ratios for the association of VP infection with potential risk factors.

RESULTS

In multivariate analysis, VP infection was associated with having pre-existing chronic disease (adjusted odds ratio [aOR], 6.0; 95% confidence interval [CI], 1.5-23.7), eating undercooked seafood (aOR, 8.0; 95% CI, 1.3-50.4), eating undercooked meat (aOR, 29.1; 95% CI, 3.0-278.2), eating food from a street food vendor (aOR, 7.6; 95% CI, 3.3-17.6), and eating vegetable salad (aOR, 12.1; 95% CI, 5.2-28.2).

CONCLUSIONS

Eating raw (undercooked) seafood and meat is an important source of VP infection among the study population. Cross-contamination of VP in other food (e.g., vegetables and undercooked meat) likely plays a more important role. Intervention should be taken to lower the risks of cross-contamination with undercooked seafood/meat, especially targeted at people with low income, transient workers, and people with medical risk factors.