Prevalence, Molecular Characterization, and Antibiotic Susceptibility of Vibrio parahaemolyticus from Ready-to-Eat Foods in China

Antimicrobial resistance and genomic analysis of Vibrio parahaemolyticus isolates from foodborne outbreaks, Huzhou, China, 2019-2023

Objective

The purpose of this study was to investigate the epidemiological and genomic characteristics of Vibrio parahaemolyticus (V. parahaemolyticus) isolates from outbreaks in Huzhou, China.

Methods

This study aims to analyze the epidemiological data on V. parahaemolyticus outbreaks reported in Huzhou from 2019 to 2023. A total of 70 V. parahaemolyticus outbreak isolates were collected. The antibiotic resistance, serotypes, molecular typing, and genomic characteristics of these isolates were analyzed.

Results

Most outbreaks of V. parahaemolyticus infection occurred in the summer, and the majority of outbreaks occurred in restaurants and rural banquets. High resistance rates were observed for ampicillin (AMP, 24.29%), followed by tetracycline (TET, 15.71%) and trimethoprim-sulfamethoxazole (SXT, 15.71%). The newly emerged serotype O10:K4 became dominant from 2021 to 2023, with most isolates belonging to ST3. The resistance gene blaCARB was frequently detected among these isolates. The pulsed-field gel electrophoresis (PFGE) and whole-genome single-nucleotide polymorphisms (wgSNPs) effectively differentiated the nine outbreaks.

Conclusion

The newly emerged serotype O10:K4 became dominant from 2021 to 2023, with most isolates being ST3. PFGE and WGS technologies provided reliable methods for typing and identifying V. parahaemolyticus for outbreaks.

The Combination of β-Glucan and Astragalus Polysaccharide Effectively Resists Nocardia seriolae Infection in Largemouth Bass (Micropterus salmoides)

Effectively treating and preventing outbreaks is crucial for improving the economic benefits of aquaculture. Therefore, utilizing immunostimulants, either alone or in combination, is regarded as a promising strategy. In this study, β-glucan + APS (200 mg/kg + 200 mg/kg), β-glucan (200 mg/kg), APS (200 mg/kg), enrofloxacin (15 mg/kg), and sulfadiazine (15 mg/kg) were added to feed to assess the effects against Nocardia seriolae infection in largemouth bass (Micropterus salmoides) within 14 days. The survival rates did not differ between the enrofloxacin group and the β-glucan + APS group, but both were significantly higher than that of the control group. Additionally, the enrofloxacin group and the β-glucan + APS group exhibited the lowest bacterial loads and tissue damage. Importantly, the β-glucan + APS treatment significantly improved serum enzyme activities (total superoxide dismutase, lysozyme, total protein) and the expression of immune genes (IL-1β, TNF-α, IFN-γ, IgM) compared to the other treatment groups. The enrofloxacin group showed similar efficacy to the β-glucan + APS group in combating N. seriolae infection, but N. seriolae in the enrofloxacin group developed drug resistance. In summary, the combined use of β-glucan and APS is a promising strategy for treating bacterial diseases, thereby contributing to the promotion of sustainable aquaculture development.

Epidemiological characteristics of Vibrio parahaemolyticus outbreaks, Zhejiang, China, 2010-2022

Background

Vibrio parahaemolyticus is one of the most common foodborne pathogens and poses a significant disease burden. The purpose of the study was to elucidate the epidemiological characteristics of Vibrio parahaemolyticus outbreaks in Zhejiang Province, and provide insights for the targeted prevention and control of foodborne diseases.

Methods

Descriptive statistical methods were utilized to analyze the data on Vibrio parahaemolyticus outbreaks reported by all Centers for Disease Control and Prevention (CDCs) through Foodborne Disease Outbreaks Surveillance System (FDOSS) in Zhejiang Province from 2010 to 2022.

Results

From 2010 to 2022, a total of 383 outbreaks caused by Vibrio parahaemolyticus were reported by 90 CDCs in 11 prefectures of Zhejiang Province, resulting in 4,382 illnesses, 326 hospitalizations and 1 death. The main symptoms of the outbreak-related cases were diarrhea (95.18%), abdominal pain (89.23%), nausea (55.64%), vomiting (50.57%), fever (24.21%), etc. The outbreaks occurring between July and September accounted for 77.54% of all outbreaks (297 out of 383). Outbreaks associated with restaurants accounted for the majority (57.96%, 222/383) of all outbreaks, followed by those linked to staff canteens (15.40%, 59/383) and rural banquets (11.23%, 43/383). 31.85% of all outbreaks were associated with the consumption of aquatic products, while ready-to-eat foods such as Chinese cold dishes and cooked meat products accounted for 12.53% of all outbreaks. Serotype O3:K6 (81.94%, 118/144) was the predominant serotype responsible for outbreaks from 2010 to 2020, while serotype O10:K4 (57.89%, 33/57) was the predominant serotype from 2021 to 2022.

Conclusion

In-depth and comprehensive analysis of long-term surveillance data on Vibrio parahaemolyticus outbreaks is essential to gain insight into the epidemiological characteristics, identify long-term patterns and recent trends, and enable governments to prioritize interventions and develop targeted policies to mitigate such outbreaks.

Surveillance of Vibrio parahaemolyticus pathogens recovered from ready-to-eat foods

This study examined the occurrence of V. parahaemolyticus from ready-to-eat (RTE) food in Delta State, Nigeria. It also characterized antibiotic resistance and virulence gene profile patterns to determine the associated health risk hazard. Food samples total of 380 were collected randomly and assessed for V. parahaemolyticus. V. parahaemolyticus isolates were characterized for their virulence and antibiogram potentials using a phenotypic and polymerase chain reaction (PCR) approach. A total of 42 (11.1%) samples were contaminated with V. parahaemolyticus. In 17/42 (40.5%) of the V. parahaemolyticus-positive samples, the densities were < 10 MPN/g. However, 19/42 (45.2%) and 6/42 (14.3%) of the samples had densities of 10 - 10² and > 10² MPN/g, respectively. A total of 67 V. parahaemolyticus isolates were identified using PCR; 54(80.6%) isolates were multidrug resistant. A total of 22 (32.8%), 39 (58.2%), and 67 (100%) of the V. parahaemolyticus harbored the tdh, trh, and tlh toxin genes, respectively. The T3SS1 gene (vcrD1) was detected in 67 (100%) of the isolates. The T3SS2α genes which were vcrD2, vopB2, and vopT were detected in 21 (31.3%), 11 (16.4%) and 30 (44.8%) of the isolates respectively. Some of the V. parahaemolytics strains harbored the orf8 gene 20 (29.9%), and a combination of orf8 + tdh genes 12 (17.9%), categorized as pandemic strains. The antibiotic resistance genes detected in this study include bla_TEM 33 (49.3), tetM 19 (28.4), cmlA 32(47.8) and sul1 14 (20.9). The concentration levels and prevalence of V. parahaemolyticus in RTE foods indicate contamination of ready-to-eat foods, particularly street foods consumed in the Delta State of Nigeria, threatening public health and consumer safety.

Quantitative Risk Assessment of Vibrio parahaemolyticus in Shellfish from Retail to Consumption in Coastal Cities of Eastern China

ABSTRACT

Vibrio parahaemolyticus is the main foodborne pathogen worldwide that causes acute gastroenteritis. A quantitative microbiological risk assessment (QMRA) was conducted to evaluate the health risk associated with V. parahaemolyticus in shellfish in the coastal cities in the eastern part of the People's Republic of China. The QMRA framework was established from shellfish at retail to cooking at home to consumption. The prevalence and level of V. parahaemolyticus in shellfish, cooking methods, storage temperature, time after purchase, shellfish consumption frequency, and consumption amount were analyzed in the exposure assessment. The results of the exposure assessment were introduced into the beta-Poisson dose-response model, and Monte Carlo analysis was used to calculate the risk of gastroenteritis from shellfish consumption. The probability of illness caused by V. parahaemolyticus from shellfish consumption per person per year (Pill,yr) was 3.49E-05. Seasonal differences were noted in the Pill/meal; the maximum was 4.81E-06 in summer and the minimum was 2.27E-07 in winter. The sensitivity analysis revealed that the level of V. parahaemolyticus in shellfish and the amount of shellfish consumed per meal were main factors contributing to illness. This QMRA provided valuable information such as the probability of illness associated with the consumption of shellfish and reference points for prevention strategies and control standards of V. parahaemolyticus in shellfish.

HIGHLIGHTS

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.

Antibiofilm and Antiquorum Sensing Potential of Lactiplantibacillus plantarum Z057 against Vibrio parahaemolyticus

Vibrio parahaemolyticus is a widespread foodborne pathogen that causes serious seafood-borne gastrointestinal infections. Biofilm and quorum sensing (QS) are critical in regulating these infections. In this study, first, the ability of Lactiplantibacillus plantarum Z057 to compete, exclude, and displace V. parahaemolyticus biofilm was evaluated. Then, the inhibitory effects of L. plantarum Z057 extract (Z057-E) on V. parahaemolyticus biofilm and QS were explored from the aspects of biofilm biomass, metabolic activity, physicochemical properties, extracellular polymer matrix content, QS signal AI-2 activity, biofilm microstructure, and the expression levels of biofilm and QS-related genes. Results showed that L. plantarum Z057 effectively inhibited biofilm formation of V. parahaemolyticus and interfered with the adhesion of V. parahaemolyticus on the carrier surface. In addition, the Z057-E could significantly reduce the biofilm biomass, metabolic activity, hydrophobicity, auto-aggregation ability, swimming and swarming migration diameter, AI-2 activity, extracellular polysaccharide (EPS), and extracellular protein content of V. parahaemolyticus. Fluorescence microscope and scanning electron microscope (SEM) images demonstrated that the Z057-E could efficiently inactivate the living cells, destroy the dense and complete biofilm architectures, and reduce the essential component of the extracellular polymer matrix. Real-time fluorescence quantitative PCR revealed that the Z057-E treatment down-regulated the expression of flagellum synthesis-related genes (flaA, flgM), EPS, and extracellular protein synthesis-related genes (cpsA, cpsQ, cpsR, ompW), QS-related genes (luxS, aphA, opaR), and hemolysin secretion-related genes (toxS, toxR) of V. parahaemolyticus. Thus, our results suggested that L. plantarum Z057 could represent an alternative biocontrol strategy against foodborne pathogens with anti-adhesive, antibiofilm, and antiquorum sensing activities.

Isolation and Characterization of a Lytic Vibrio parahaemolyticus Phage vB_VpaP_GHSM17 from Sewage Samples

Vibrio parahaemolyticus is a major foodborne pathogen and the main cause of diarrheal diseases transmitted by seafood such as fish, shrimp, and shellfish. In the current study, a novel lytic phage infecting V. parahaemolyticus, vB_VpaP_GHSM17, was isolated from the sewage of a seafood market, Huangsha, Guangzhou, and its morphology, biochemistry, and taxonomy features were identified. Morphological observation revealed that GHSM17 had an icosahedral head with a short, non-contractile tail. The double-stranded DNA genome of GHSM17 consisted of 43,228 bp with a GC content of 49.42%. In total, 45 putative ORFs were identified in the GHSM17 genome. Taxonomic analysis indicated GHSM17 belonging to genus Maculvirus, family Autographiviridae. In addition, GHSM17 was stable over a wide range of temperatures (20-60 °C) and pH (5-11) and was completely inactivated after 70 min of ultraviolet irradiation. The bacterial inhibition assay revealed that GHSM17 could inhibit the growth of V. parahaemolyticus within 8 h. The results support that phage GHSM17 may be a potential candidate in the biological control of V. parahaemolyticus contamination in aquaculture.

Pre-treatment of Nile tilapia (Oreochromis niloticus) with ozone nanobubbles improve efficacy of heat-killed Streptococcus agalactiae immersion vaccine

Nanobubble technology has shown appealing technical benefits and potential applications in aquaculture. We recently found that treatment with ozone nanobubbles (NB-O₃) activated expression of several immune-related genes leading to effective response to subsequent exposure to fish pathogens. In this study, we investigated whether pre-treatment of Nile tilapia (Oreochromis niloticus) with NB-O₃ can enhance specific immune responses and improve efficacy of immersion vaccination against Streptococcus agalactiae. Spleen and head kidney of fish in the vaccinated groups showed a substantial upregulation in expression levels of pro-inflammatory cytokine genes (IL-1β, TNF-α, IL-6) and immunoglobulin classes (IgM, IgD, IgT) compared with the unvaccinated control groups. The mRNA transcript of pro-inflammatory cytokine genes was greatest (approx. 2.8-3.3 folds) on day 7 post-vaccination, whereas the relative expression of immunoglobulin genes was greatest (approx. 3.2-4.1 folds) on day 21 post-immunization. Both systemic and mucosal IgM antibodies were elicited in vaccinated groups. As the result, the cumulative survival rate of the vaccinated groups was found to be higher than that of the unvaccinated groups, with a relative percent survival (RPS) ranging from 52.9 to 70.5%. However, fish in the vaccinated groups that received pre-treatment with NB-O₃, bacterial antigen uptakes, expression levels of IL-1β, TNF-α, IL-6,IgM, IgD, and IgT, as well as the specific-IgM antibody levels and percent survival, were all slightly or significantly higher than that of the vaccinated group without pre-treatment with NB-O₃. Taken together, our findings suggest that utilizing pre-treatment with NB-O₃ may improve the immune response and efficacy of immersion vaccination in Nile tilapia.

Characterization of the Novel Phage vB_VpaP_FE11 and Its Potential Role in Controlling Vibrio parahaemolyticus Biofilms

Vibrio parahaemolyticus causes aquatic vibriosis. Its biofilm protects it from antibiotics; therefore, a new different method is needed to control V. parahaemolyticus for food safety. Phage therapy represents an alternative strategy to control biofilms. In this study, the lytic Vibrio phage vB_VpaP_FE11 (FE11) was isolated from the sewers of Guangzhou Huangsha Aquatic Market. Electron microscopy analysis revealed that FE11 has a typical podovirus morphology. Its optimal stability temperature and pH range were found to be 20–50 °C and 5–10 °C, respectively. It was completely inactivated following ultraviolet irradiation for 20 min. Its latent period is 10 min and burst size is 37 plaque forming units/cell. Its double-stranded DNA genome is 43,397 bp long, with a G + C content of 49.24% and 50 predicted protein-coding genes. As a lytic phage, FE11 not only prevented the formation of biofilms but also could destroy the formed biofilms effectively. Overall, phage vB_VpaP_FE11 is a potential biological control agent against V. parahaemolyticus and the biofilm it produces.

Research on the drug resistance mechanism of foodborne pathogens

Foodborne diseases caused by foodborne pathogens are one of the main problems threatening human health and safety. The emergence of multi-drug resistant strains due to the abuse of antibiotics has increased the difficulty of clinical treatment. Research on the drug resistance mechanism of foodborne pathogens has become an effective method to solve multi-drug resistant strains. In this paper, the four main drug resistance mechanisms, including reduced cell membrane permeability, efflux pump mechanism, target site mutation mechanism, and enzymatic hydrolysis, were used to systematically analyze the drug resistance of Salmonella, Listeria monocytogenes, and Escherichia coli. And the new methods were discussed that may be used to solve the drug resistance of foodborne pathogens such as CRISPR and bacteriophages. This review provided a certain theoretical basis for the treatment of foodborne diseases.

Prevalence and Antibiogram of Vibrio parahaemolyticus and Aeromonas hydrophila in the Flesh of Nile Tilapia, with Special Reference to Their Virulence Genes Detected Using Multiplex PCR Technique

Vibrio parahaemolyticus and Aeromonas hydrophila are major public health problems and the main cause of bacterial disease in Nile tilapia (Oreochromis niloticus). This study was conducted to determine the prevalence, antibiotic resistance and some virulence genes of both V. parahaemolyticus and A. hydrophila isolates from Nile tilapia. From Manzala Farm at Dakahlia governorate, 250 freshwater fish samples were collected. The confirmed bacterial isolates from the examined Nile tilapia samples in the study were 24.8% (62/250) for V. parahaemolyticus and 19.2% (48/250) for A. hydrophila. multiplex PCR, revealing that the tlh gene was found in 46.7% (29/62) of V. parahaemolyticus isolates, while the tdh and trh virulence genes were found in 17.2% (5/29). Meanwhile, 39.5% (19/48) of A. hydrophila isolates had the 16s rRNA gene and 10.5% (2/19) had the aerA and ahh1 virulence genes. The Multiple Antibiotic Resistance indices of V. parahaemolyticus and A. hydrophila were 0.587 and 0.586, respectively. In conclusion, alternative non-antibiotic control strategies for bacterial infections in farmed fish should be promoted to avoid multidrug-resistant bacteria. Therefore, it is suggested that farmers should be skilled in basic fish health control and that molecular detection methods are more rapid and cost-effective than bacteriological methods.

Diversity of Vibrio parahaemolyticus in marine fishes of Bangladesh

AIMS

To determine the occurrence, diversity, antibiotic resistance and biofilm formation of Vibrio parahaemolyticus isolated from marine fishes in Bangladesh.

METHODS AND RESULTS

A total of 80 marine fishes were obtained from the local markets and examined for the presence of V. parahaemolyticus. All the isolated V. parahaemolyticus were characterized for the presence of virulence markers, thermostable direct hemolysin (TDH) or thermostable direct hemolysin related hemolysin (TRH). Isolates were serotyped and further characterized by enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) typing to analyse the genetic diversity. Moreover, biofilm formation and antibiotic resistance patterns were also determined. About 63·75% (51/80) of the tested marine fishes were contaminated with V. parahaemolyticus. From the contaminated fishes, 71 representatives V. parahaemolyticus were isolated and none of them harboured tdh and trh virulence genes. Nine different O-groups and seven different K-types were found by serological analysis and the dominant serotype was O5:KUT. In ERIC-PCR analysis, eight clusters (A-H) were found and the most common pattern was A (46·5%). All of the isolates were resistant to ampicillin and 78·9% of isolates were resistant to streptomycin. The highest biofilm formation was found at 37°C compared to 25°C and 4°C.

CONCLUSION

Diverse V. parahaemolyticus are present in marine fishes in the local market of Bangladesh with antibiotic-resistant properties and biofilm formation capacity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The widespread prevalence of diverse V. parahaemolyticus in marine fishes is an issue of serious concern, and it entails careful monitoring to ascertain the safety of seafood consumers.

Virulence, resistance, and genetic diversity of Vibrio parahaemolyticus recovered from commonly consumed aquatic products in Shanghai, China

Vibrio parahaemolyticus can cause severe gastroenteritis, septicaemia and even death in humans. Continuous monitoring of V. parahaemolyticus contamination in aquatic products is imperative for ensuring food safety. In this study, we isolated and characterized 561 V. parahaemolyticus strains recovered from 23 species of commonly consumed shellfish, crustaceans, and fish collected in July and August of 2017 in Shanghai, China. The bacterium was not isolated from two fish species Carassius auratus and Parabramis pekinensis. The results revealed a very low occurrence of pathogenic V. parahaemolyticus carrying the toxin genes trh (0.2%) and tdh (0.0%). However, high percentages of resistance to the antimicrobial agents ampicillin (93.0%), rifampin (82.9%), streptomycin (75.4%) and kanamycin (50.1%) were found. A high incidence of tolerance to the heavy metals Hg²⁺ (74.7%) and Zn²⁺ (56.2%) was also observed in the isolates. ERIC-PCR-based fingerprinting of MDR isolates (77.5%) revealed 428 ERIC-genotypes, demonstrating remarkable genetic variation among the isolates. The results of this study support the urgent need for food safety risk assessment of aquatic products.

Metagenomic characterization of bacterial community and antibiotic resistance genes in representative ready-to-eat food in southern China

Ready-to-eat (RTE) foods have been considered to be reservoirs of antibiotic resistance bacteria, which constitute direct threat to human health, but the potential microbiological risks of RTE foods remain largely unexplored. In this study, the metagenomic approach was employed to characterize the comprehensive profiles of bacterial community and antibiotic resistance gene (ARG) in 18 RTE food samples (8 RTE meat, 7 RTE vegetables and 3 RTE fruit) in southern China. In total, the most abundant phyla in RTE foods were Proteobacteria, Firmicutes, Cyanobacteria, Bacteroidetes and Actinobacteria. 204 ARG subtypes belonging to 18 ARG types were detected with an abundance range between 2.81 × 10⁻⁵ and 7.7 × 10⁻¹ copy of ARG per copy of 16S rRNA gene. Multidrug-resistant genes were the most predominant ARG type in the RTE foods. Chloramphenicol, macrolide-lincosamide-streptogramin, multidrug resistance, aminoglycoside, bacitracin, tetracycline and β-lactam resistance genes were dominant, which were also associated with antibiotics used extensively in human medicine or veterinary medicine/promoters. Variation partitioning analysis indicated that the join effect of bacterial community and mobile genetic elements (MGEs) played an important role in the resistome alteration. This study further deepens the comprehensive understanding of antibiotic resistome and the correlations among the antibiotic resistome, microbiota, and MGEs in the RTE foods.

Microevolution of Vibrio parahaemolyticus Isolated from Clinical, Acute Hepatopancreatic Necrosis Disease Infecting Shrimps, and Aquatic Production in China

Vibrio parahaemolyticus is the leading cause of bacteria-associated foodborne diarrheal diseases and specifically causes early mortality syndrome (EMS), which is technically known as acute hepatopancreatic necrosis disease (AHPND), a serious threat to shrimp aquaculture. To investigate the genetic and evolutionary relationships of V. parahaemolyticus in China, 184 isolates from clinical samples (VPC, n=40), AHPND-infected shrimp (VPE, n=10), and various aquatic production sources (VPF, n=134) were collected and evaluated by a multilocus sequence analysis (MLST). Furthermore, the presence of potential virulence factors (tlh, tdh, and trh) and single nucleotide polymorphisms (SNPs) in V. parahaemolyticus isolates was assessed using genomic sequencing. Analyses of virulence factors revealed that the majority of VPC isolates (97.5%) possessed the tdh and/or trh genes, while most of the VPF isolates (83.58%) did not encode hemolysin genes. Therefore, we hypothesized that the environment is a potential reservoir that promotes horizontal DNA transfer, which drives evolutionary change that, in turn, leads to the emergence of novel, potentially pathogenic strains. Phylogenetic analyses identified VPF-112 as a non-pathogenic maternal strain isolated from aquatic products and showed that it had a relatively high evolutionary status. All VPE strains and some VPC strains were grouped into several small subgroups and evenly distributed on phylogenetic trees. Anthropogenic activities and environmental selective pressure may be important factors influencing the process of transforming strains from non-pathogenic to pathogenic bacteria.

A database for risk assessment and comparative genomic analysis of foodborne Vibrio parahaemolyticus in China

Vibrio parahaemolyticus is a major foodborne pathogen worldwide. The increasing number of cases of V. parahaemolyticus infections in China indicates an urgent need to evaluate the prevalence and genetic diversity of this pathogenic bacterium. In this paper, we introduce the Foodborne Vibrio parahaemolyticus genome database (FVPGD), the first scientific database of foodborne V. parahaemolyticus distribution and genomic data in China, based on our previous investigations of V. parahaemolyticus contamination in different kinds of food samples across China from 2011 to 2016. The dataset includes records of 2,499 food samples and 643 V. parahaemolyticus strains from supermarkets and marketplaces distributed over 39 cities in China; 268 whole-genome sequences have been deposited in this database. A spatial view on the risk situations of V. parahaemolyticus contamination in different food types is provided. Additionally, the database provides a functional interface of sequence BLAST, core genome multilocus sequence typing, and phylogenetic analysis. The database will become a powerful tool for risk assessment and outbreak investigations of foodborne pathogens in China.

Prevalence, antibiotic susceptibility and characterization of Vibrio parahaemolyticus isolates in China

Vibrio parahaemolyticus is a marine and estuarine bacterium that poses a major threat to human health worldwide. In this study, from 2017 to 2019, we evaluated 900 food samples collected from China in 2017, with the aim of determining the incidence and features of V. parahaemolyticus in ready-to-eat (RTE) foods, shrimp and fish in China. The contamination rates in these were 3.67, 19.33 and 10.67%, respectively, and the prevalence of V. parahaemolyticus was higher in summer than in winter. In addition, 101 V. parahaemolyticus strains were isolated. Our results suggested that most of the isolates were resistant to aminoglycosides based on the antimicrobial resistance patterns of these aquatic product isolates against 14 antimicrobial agents. Furthermore, most of the isolates were multidrug-resistant. Serotyping showed that the isolates of the O2 serotype comprised the maximum proportion. Enterobacterial repetitive intergenic consensus sequence (ERIC)-PCR results indicated that the isolates (n = 101) could be classified into 12 clusters. There were 82 STs suggesting genetic variation and relatedness among these isolates. Our findings demonstrated the presence of V. parahaemolyticus in foods from Chinese retail markets and show that this methodology can be used for microbiological risk assessment in China.

Food-Borne Vibrio parahaemolyticus in China: Prevalence, Antibiotic Susceptibility, and Genetic Characterization

Vibrio parahaemolyticus is a marine and estuarine bacterium that leads to damage of aquatic industry by foodborne outbreaks and possesses an enormous threat to food safety as well as human health worldwide. In the current study, we investigated 905 food samples (ready-to-eat foods, fish, and shrimp) from 15 provinces in China, and aimed to determine prevalence, biological characteristics and genetic diversity of presumptive V. parahaemolyticus isolates. Firstly, 14.17% of 240 fish samples, 15.34% of 365 shrimp samples and 3.67% of 300 RTE food samples were positive for potential V. parahaemolyticus. Secondly, 69 food samples (14.87%) collected in summer were positive for target isolates, while the rate of positive sample of 441 food samples in winter reached 7.26%. Thirdly, we purified 202 V. parahaemolyticus strains for further research. And antimicrobial susceptibility results of strains tested revealed that the highest resistance rate was observed for ampicillin (79.20%). At the same time, 148 (73.27%) of all isolates were classified and defined as multi-drug resistant foodborne bacteria. The results of PCR assay showed that the isolates being positive for the tdh, trh or both genes, were up to 9.90%, 19.80% or 3.96%. Besides, multiplex PCR test showed that the isolates carrying O2 serogroup were the most prevalent. Furthermore, sequence types (STs) of 108 isolates were obtained via multi-locus sequence typing. Not only 82 STs were detected, but also 41 of which were updated in the MLST database. Thus, our findings significantly demonstrated the high contamination rates of V. parahaemolyticus in fish and shrimp and it may possess potential threat for consumer health. We also provided up-to-date dissemination of antibiotic-resistant V. parahaemolyticus which is important to ensure the high efficacy in the treatment of human and aquatic products infections. Lastly, with the identification of 82 STs including 41 novel STs, this study significantly revealed the high genetic diversity among V. parahaemolyticus. All of our research improved our understanding on microbiological risk assessment in ready-to-eat foods, fish, and shrimp.

Isolation, Molecular Characterization and Antibiotic Susceptibility Pattern of Vibrio parahaemolyticus from Aquatic Products in the Southern Fujian Coast, China

Vibrio parahaemolyticus is a major gastroenteritis-causing pathogen in many Asian countries. Antimicrobial resistance in V. parahaemolyticus has been recognized as a critical threat to food safety. In this study, we determined the prevalence and incidence of antimicrobial resistance in V. parahaemolyticus in the southern Fujian coast, China. A total of 62 isolates were confirmed in retail aquatic products from June to October of 2018. The serotype O3:K6 strains, the virulence genes tdh and trh, antibiotic susceptibility and molecular typing were investigated. Then plasmid profiling analysis and curing experiment were performed for multidrug-resistant strains. The results showed that the total occurrence of V. parahaemolyticus was 31% out of 200 samples. Five strains (8.1%) out of 62 isolates were identified as the V. parahaemolyticus O3:K6 pandemic clone. A large majority of isolates exhibited higher resistance to penicillin (77.4%), oxacillin (71%), ampicillin (66.1%) and vancomycin (59.7%). Seventy-one percent (44/62) of the isolates exhibited multiple antimicrobial resistance. All 62 isolates were grouped into 7 clusters by randomly amplified polymorphic DNA, and most of the isolates (80.6%) were distributed within cluster A. Plasmids were detected in approximately 75% of the isolates, and seven different profiles were observed. Seventy-six percent (25/33) of the isolates carrying the plasmids were eliminated by 0.006% SDS incubated at 42°C, a sublethal condition. The occurrence of multidrug-resistant strains could be an indication of the excessive use of antibiotics in aquaculture farming. The rational use of antimicrobial agents and the surveillance of antibiotic administration may reduce the acquisition of resistance by microorganisms in aquatic ecosystems.

Co-occurrence of Antibiotic and Heavy Metal Resistance and Sequence Type Diversity of Vibrio parahaemolyticus Isolated From Penaeus vannamei at Freshwater Farms, Seawater Farms, and Markets in Zhejiang Province, China

Vibrio parahaemolyticus is the leading cause of seafood-borne bacterial poisoning in China and is a threat to human health worldwide. The aim of this study was to assess the antibiotic resistance profiles and distribution of heavy metal resistance of V. parahaemolyticus isolates from Penaeus vannamei from freshwater farms, seawater farms, and their corresponding markets in Zhejiang, China and to assess the relationship between multidrug resistance (MDR) and multi-heavy metal resistance (MHMR). Of the 360 P. vannamei samples that we tested, 90 (25.00%) were V. parahaemolyticus positive, but the occurrence of pathogenic isolates carrying the toxin genes tdh (4.44%) and trh (3.33%) was low. None of the tested isolates harbored both the tdh and trh genes. However, antibiotic resistance profiles varied among different sampling locations, levels of resistance to the antibiotics ampicillin (76.67%) and streptomycin (74.44%) were high overall, and MDR isolates were common (40.00% of all isolates). Heavy metal resistance patterns were similar among the different sampling locations. Overall, the majority of V. parahaemolyticus isolates displayed tolerance to Cd²⁺ (60.00%), and fewer were resistant to Cu²⁺ (40.00%), Zn²⁺ (38.89%), Ni²⁺ (24.44%), Cr³⁺ (14.44%), and Co²⁺ (8.89%). In addition, 34.44% (31/90) of isolates tested in this study were found to be MHMR. Using Pearson's correlation analysis, MDR and MHMR were found to be positively correlated (P = 0.004; R = 0.759). The 18 V. parahaemolyticus isolates that were both MDR and MHMR represented 18 sequence types, of which 12 were novel to the PubMLST database, and displayed a high level of genetic diversity, suggesting that dissemination may be affected by mobile genetic elements via horizontal gene transfer. However, a low percentage of class 1 integrons without gene cassettes and no class 2 or 3 integrons were detected in the 18 MDR and MHMR isolates or in the 90 V. parahaemolyticus isolates overall. Thus, we suggest that future research focus on elucidating the mechanisms that lead to a high prevalence of resistance determinants in V. parahaemolyticus. The results of this study provide data that will support aquatic animal health management and food safety risk assessments in the aquaculture industry.

High genetic diversity of Vibrio parahaemolyticus isolated from tidal water and mud of southern coast of South Korea

A horizontal, fluorophore-enhanced, repetitive extragenic palindromic-polymerase chain reaction (rep-PCR) DNA fingerprinting technique was adapted to examine the genotypic richness and source differentiation of Vibrio parahaemolyticus (n = 1749) isolated from tidal water and mud of southern coast of South Korea. The number of unique genotypes observed from June (163, 51.9%), September (307, 63.9%), December (205, 73.8%) and February (136, 74.7%), indicating a high degree of genetic diversity. Contrary, lower genetic diversity was detected in April (99, 46.8%), including predominant genotypes comprised >30 V. parahaemolyticus isolates. Jackknife analysis indicated that 65.1% tidal water isolates and 87.1% mud isolates were correctly assigned to their source groups. Sixty-nine isolates of pathogenic V. parahaemolyticus were clustered into two groups, separated by sampling month, source of isolation and serogroups. Serotypes O1, O4, O5, O10/O12 and O11 were the dominant serovariants, while serotypes O3/O13 were highly detected in April where there were no pathogenic V. parahaemolyticus isolates. Most of the V. parahaemolyticus isolates were resistant to ampicillin, ceftazidime and sulfamethoxazole. Interestingly, four V. parahaemolyticus isolates resistant to carbepenem did not contain the known carbapenemase-encoding gene, but possess an extended-spectrum β-lactamase blaTEM.

Prevalence, Virulence Characterization, AMR Pattern and Genetic Relatedness of Vibrio parahaemolyticus Isolates From Retail Seafood of Kerala, India

Vibrio parahaemolyticus, a halophilic bacterium often found in the marine or estuarine environment is a well-known enteropathogen responsible for foodborne outbreaks associated with seafood. The pathogenic strains of V. parahaemolyticus are marked by the presence of thermostable direct hemoylsin (tdh) and/or TDH related hemolysin (trh) genes. This study aimed to investigate the prevalence and characteristics of potentially pathogenic V. parahaemolyticus in selected retail markets of Cochin, Kerala, along the south-western coast of the Indian subcontinent. One hundred samples collected from 10 retail markets were analyzed for the presence of pathogenic isolates of V. parahaemolyticus. Out of the 721 presumptive isolates, 648 were confirmed to be V. parahaemolyticus by toxR gene amplification, among which 29 were Kanagawa phenomenon (KP) positive. Among these potentially pathogenic isolates, 17 possessed the tdh gene whereas none of them had the trh gene. The faint amplification bands produced during the amplification of tdh gene from two isolates was confirmed by sequencing. Multiplex O serotyping identified O1 serotype as the most prevalent serotype among the 29 potentially pathogenic isolates. Further, studies on the pandemic nature of these isolates revealed that 14 of the 29 were positive for the PGS-PCR, whereas all the isolates were negative for GS-PCR and HU-α PCR. The antibiogram of the isolates revealed that three isolates had significant Multiple Antibiotic Resistance (MAR) index of 0.2 or above. Pathogenic isolates resistant to second, third and fourth generation Cephalosporins were found to be present in the seafood studied. The molecular fingerprinting studies using ERIC-PCR, and PFGE revealed that three of these isolates shared close genetic similarities with the clinical strains. The environmental and seafood isolates that produced faint amplification bands during the amplification of tdh gene suggests that the tdh gene often goes undetected in environmental isolates. The conventional methods used to identify the pathogenic V. parahaemolyticus would be good for clinical isolates, but a more elaborate method is recommended for the detection of tdh gene in environmental isolates. This is the first comprehensive study on pathogenic V. parahaemolyticus in Kerala, India and demonstrates for the first time, the isolation of potentially pathogenic V. parahaemolyticus, carrying tdh gene from seafood collected from retail markets in Kerala.

Characterization of class 1 integrons harboring blaVEB-1 in Vibrio parahaemolyticus isolated from ready-to-eat foods in China

The aim of this study is to investigate the prevalence of integrons and integron-associated antibiotic resistance in V. parahaemolyticus strains collected from RTE foods in China, and to carry out a comprehensive analysis on the molecular characterization of V. parahaemolyticus strains carrying bla_VEB-1-positive class 1 integron. Of the 51 V. parahaemolyticus strains isolated from RTE food samples, none of the isolates was found to carry integrase genes intI2 and IntI3. However, all 51 strains were positive to integrase gene intI1, and only 2 of 51 (3.92%) intI1-positive isolates yielded polymerase chain reaction (PCR) products of gene cassette amplification. Sequence data and BLAST analysis indicated the gene cassette arrays of class 1 integron in VP007 is dfrA14-bla_VEB-1-aadB, while the gene cassette arrays of class 1 integron in V187 is bla_VEB-1-aadB-arr2-cmlA-bla_OXA-10-aadA1. Antimicrobial susceptibility testing showed that the two V. parahaemolyticus isolates harboring class 1 integrons exhibited multi-drug resistance to various antibiotics. S1-PFGE and Southern blot analysis confirmed the class 1 integron harboring bla_VEB-1 gene in V187 was located on the plasmid of ~175 kb and transferrable to the recipient strain by conjugation. This is the first detection of class 1 integrons harboring the ESBL gene bla_VEB-1 in V. parahaemolyticus. To the best of our knowledge, this is also the first report of VEB-producing V. parahaemolyticus from RTE foods. Our findings revealed that class 1 integron on conjugative plasmid contributes significantly to the dissemination of VEB-producing V. parahaemolyticus, which warrants further investigation because of the public health threat it poses.

Isolation and Characterization of the Novel Phages vB_VpS_BA3 and vB_VpS_CA8 for Lysing Vibrio parahaemolyticus

Accumulating evidence has indicated that the multiple drug resistant Vibrio parahaemolyticus may pose a serious threat to public health and economic concerns for humans globally. Here, two lytic bacteriophages, namely vB_VpS_BA3 and vB_VpS_CA8, were isolated from sewage collected in Guangzhou, China. Electron microscopy studies revealed both virions taxonomically belonged to the Siphoviridae family with icosahedral head and a long non-contractile tail. The double-stranded DNA genome of phage BA3 was composed of 58648 bp with a GC content of 46.30% while phage CA8 was 58480 bp with an average GC content of 46.42%. In total, 85 putative open reading frames (ORFs) were predicted in the phage BA3 genome while 84 were predicted in that of CA8. The ORFs were associated with phage structure, packing, host lysis, DNA metabolism, and additional functions. Furthermore, average nucleotide identity analysis, comparative genomic features and phylogenetic analysis revealed that BA3 and CA8 represented different isolates but novel members of the family, Siphoviridae. Regarding the host range of the 61 V. parahaemolyticus isolates, BA3 and CA8 had an infectivity of 8.2 and 36.1%, respectively. Furthermore, ∼100 plaque-forming units (pfu)/cell for phage BA3 and ∼180 pfu/cell for phage CA8 were determined to be the viral load under laboratory growth conditions. Accordingly, the phage-killing assay in vitro revealed that phage CA8 achieved approximately 3.65 log unit reductions. The present results indicate that CA8 is potentially applicable for biological control of multidrug resistant V. parahaemolyticus.

Prevalence, virulence, antimicrobial resistance, and molecular characterization of fluoroquinolone resistance of Vibrio parahaemolyticus from different types of food samples in China

Vibrio parahaemolyticus is the leading cause of foodborne bacterial poisoning in China. The aim of this research is to conduct a study on the prevalence, virulence, and antimicrobial resistance of V. parahaemolyticus from different types of food samples in 12 different cities of China. Since fluoroquinolones are the major choice of treatment for V. parahaemolyticus infections, the genetic basis for fluoroquinolone resistance in V. parahaemolyticus were also investigated. V. parahaemolyticus was detected in 163 of the 784 food samples collected from 12 different cities in China, resulting in a prevalence of 20.79%. The prevalence of V. parahaemolyticus in ready-to-eat (RTE) food (4.96%) was much lower than those of shrimp (32.62%) and fish (22.00%). Virulence gene screening showed that 44 (27.00%) V. parahaemolyticus strains carried at least one virulence gene. Four isolates from shrimp and three isolates from fish contained both the virulence genes tdh and trh. In addition, the trh was firstly detected in one isolate collected from RTE food. All isolates exhibited relatively high resistance rates to ampicillin (82.21%), gentamicin (19.63%), and tetracycline (14.11%), while <10% of strains were resistant to ciprofloxacin (4.91%), levofloxacin (4.91%), and tetracycline (4.29%). Eight fluoroquinolone-resistant V. parahaemolyticus were selected to determine the molecular basis for fluoroquinolone resistance. These eight isolates belonged to three different types according to enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR). A Ser83Ile substitution in GyrA was deteted in seven fluoroquinolone-resistant strains, except V209 which harbored a Ser83Phe substitution in GyrA. Moreover, A Ser85Leu substitution in ParC was found in five isolates (V52, V53, V61, V163, and V209). Plasmid-mediated quinolone resistance (PMQR) genes were detected in all eight fluoroquinolone-resistant V. parahaemolyticus strains. This is the first report of Ser83Phe substitution in GyrA, qnrD and qnrS1 in V. parahaemolyticus. The information generated in this study will provide valuable information for risk assessment of V. parahaemolyticus infections and future control of antibiotic-resistant V. parahaemolyticus species in China.

Application of digital PCR and next generation sequencing in the etiology investigation of a foodborne disease outbreak caused by Vibrio parahaemolyticus

Globally, V. parahaemolyticus infection is a leading cause of bacterial diarrheal diseases. Pathogenic V. parahaemolyticus strains that produce hemolysins are responsible for these diseases. The composition of pathogenic and non-pathogenic V. parahaemolyticus and the change of the bacterial composition before and after traditional selective enrichment in a single sample associated with disease outbreak remain unclear. We investigated an outbreak by using next generation sequencing and digital PCR to address those questions. NGS showed that the V. parahaemolyticus caused the outbreak belonged to s single clone. In contrast, among the seven non-pathogenic V. parahaemolyticus isolated from the suspected food sample, 4 serotypes and 6 PFGE patterns were identified. And nearly 70,000 SNPs were identified among the non-pathogenic strains. This result confirmed that the outbreak was caused by V. parahaemolyticus. Furthermore, NGS results clearly showed the diversity of non-pathogenic V. parahaemolyticus in a single contaminated food sample. The ratios of non-pathogenic and pathogenic V. parahaemolyticus were 31.41 and 620.11 in the original and enriched food samples respectively showed by digital PCR. Meta-genomic data indicated the top 3 species were Weissella cibaria, Weissella confusa, and Enterobacter cloacae in the original food sample, and Vibrio sp Ex25, Vibrio sp 712i, and V. parahaemolyticus in the enriched sample. Therefore, the combing of NGS and digital PCR results showed that traditional Vibrio selective enrichment media could facilitate the growth of Vibrios, however, it provided no advantages to pathogenic V. parahaemolyticus. Hence, our results indicated that the traditional culture methods alone may lead to wrong conclusions and so improvements in culture methods are needed.

Attenuation of Multiple Vibrio parahaemolyticus Virulence Factors by Citral

Citral was known as a widely used food additive with antimicrobial activity; however, whether it can be a potential therapy for controlling bacterial virulence with less risk of antimicrobial resistance remains to be investigated. Herein, we demonstrated that Vibrio parahaemolyticus virulence factors that contribute to infection were effectively inhibited to different degrees by sub-inhibitory concentrations (3.125, 6.25, and 12.5 μg/ml) of citral. Citral exerted strong inhibition of autoinducer-2 production and adhesion to Caco-2 cells. Biofilm formation of V. parahaemolyticus was effectively decreased by citral at 30°C and 20°C. Moreover, citral repressed the transcription of genes related to flagella biosynthesis, biofilm formation, type III secretion effectors, and antibiotic resistance, as well as genes contributing to the regulation of quorum sensing and toxin production. Therefore, citral could effectively attenuate multiple virulence properties of V. parahaemolyticus, and its effect on in vivo infection by V. parahaemolyticus needs further investigation.

Comparative Genomic Analysis Reveals the Potential Risk of Vibrio parahaemolyticus Isolated From Ready-To-Eat Foods in China

Vibrio parahaemolyticus is a major foodborne pathogen associated with the consumption of aquatic products. The presence of this bacterium in ready-to-eat (RTE) foods has recently been reported. However, the genomic features and potential risks of V. parahaemolyticus isolated from RTE foods are poorly understood. To help understand the genome-wide characteristics of RTE food isolates, the complete genomes of 27 RTE food isolates were sequenced and compared to those of 20 clinical and 19 other environmental (e.g., water and aquatic product source) isolates using a comparative genomics approach. Analysis revealed that V. parahaemolyticus RTE food isolates had higher numbers of genes on average and possessed more accessory genes than isolates from other sources. Most RTE food isolates were positive for some known virulence-associated genes and pathogenicity islands (PAIs), and some of these isolates were genetically homologous to clinical isolates. Genome-wide association analysis revealed 79 accessory genes and 78 missense single-nucleotide polymorphisms that affected 11 protein-coding genes were significantly associated with RTE food sources. These genes were mostly involved in defense mechanisms and energy production and conversion according to functional annotation in the COG database. KEGG Pathway analysis showed that these genes mainly affected the biofilm formation of V. parahaemolyticus, and subsequent experiments confirmed that nearly all RTE food isolates possessed the ability to form biofilm. The biofilm formation can facilitate the persistence of V. parahaemolyticus in RTE foods, and the presence of virulence-associated genes poses a pathogenic potential to humans. Our findings highlight the potential risk of V. parahaemolyticus in Chinese RTE foods and illustrate the genomic basis for the persistence of these isolates. This study will aid in re-evaluating the food safety threats conferred by this bacterium.

Staphylococcus aureus Isolated From Retail Meat and Meat Products in China: Incidence, Antibiotic Resistance and Genetic Diversity

This study was to estimate the prevalence and characteristics of Staphylococcus aureus from 1,850 retail meat and meat products in China during July 2011 to June 2016. The samples were collected covering most provincial capitals in China, including 604 raw meat, 601 quick-frozen meat, and 645 ready-to-eat meat. Using the qualitative and quantitative methods, all 39 cities had S. aureus-positive samples, and S. aureus was detected in 35.0% (647/1,850) of the samples. The levels of S. aureus in retail meat showed that the MPN value of the majority of the positive samples ranged from 0.3 to 100 MPN/g. Twenty-four antibiotics were used to test all 868 S. aureus isolates for antibiotic susceptibility. Only 11 isolates (1.26%) were susceptible to all antibiotics, whereas most isolates (821/868, 94.6%) showed resistance or intermediary resistance to more than three or more antibiotics. Of these strains, 104 (12.0%) were resistant to more than 10 antibiotics. However, the most frequent resistance was observed to ampicillin (85.4%), followed by penicillin (84.6%), erythromycin (52.7%), tetracycline (49.3%), kanamycin (45.3%), telithromycin (30.1%), clindamycin (29.6%), streptomycin (21.1%), norfloxacin (20.4%), gentamicin (19.4%), fusidic acid (18.4%), ciprofloxacin (16.9%), chloramphenicol (13.1%), amoxycillin/clavulanic acid (11.0%), and others (<10%). 7.4% of isolates (62/868) were confirmed as methicillin-resistance S. aureus (MRSA). By molecular typing analysis, there were 164 spa types and 111 STs were identified, including 15 novel spa types and 65 newly STs by multilocus sequence typing (MLST) and spa typing. Despite the wide genetic diversity observed among the 868 isolates, a great proportion of the population belonged to finite number of major clones: ST1-t127 (93/868, 10.7%) and ST7-t091 (92/868, 10.6%), ST5-t002 (42/868, 4.8%), ST398-t034 (40/868, 4.6%), ST188-t034 (38/868, 4.4%), ST59-t437 (30/868, 3.5%), ST6-t701 (29/868, 3.3%), and ST9-t899 (27/868, 3.1%) in China. This study reflects S. aureus was readily detected in Chinese retail meat and meat products but the level were not very excessive. In this study, the high antibiotic resistance is alarming and raising public health concern. In additions, most of molecular types of isolates have been linked to human infections around the world, indicating that these types of S. aureus in China have a theoretical pathogenic potential.

Construction, immune protection and innate immune response of shuffled polyvalent ompAs vaccines

Our previous studies demonstrated that molecular breeding via DNA shuffling directs the evolution of polyvalent vaccines with desired traits, which leads to generation of polyvalent ompA vaccines using Vibrio alginolyticus VA0764 primers. Here, we replaced VA0764 primers with Edwardsiella tarda ompA primers to generate new polyvalent ompA vaccines by DNA shuffling of the same five ompA genes from four species of bacteria E. tarda, V. parahaemolyticus, V. alginolyticus and Escherichia coli. We identified four polyvalent vaccine candidates from a eukaryotic expressing library EompAs-FE containing 82 ompAs using active immune protection against V. alginolyticus and E. tarda. Furthermore, we explored mechanisms of polyvalent vaccine candidates by investigation of the innate immune response to these ompAs, and found that expression of IL-1β, IL-8, IL-15, COX-2, IFN-γ, TLR-1, TLR-3 and C3b genes was elevated as a characteristic feature of these polyvalent vaccine candidates. These results indicate that use of different primers to construct a DNA library selects new evolution of polyvalent vaccines with desired traits, and polyvalent ompA vaccines elicit high innate immune response.

Prevalence, Antibiotic Susceptibility and Diversity of Vibrio parahaemolyticus Isolates in Seafood from South China

Vibrio parahaemolyticus is a leading cause of foodborne infections in China and a threat to human health worldwide. The main objective of this study is to determine the prevalence and characteristic of V. parahaemolyticus isolates in fish, oyster and shrimp samples from the South China domestic consumer market. To accomplish this, we examined 504 seafood samples from 11 provinces of China. The prevalence rates were 9.38, 30.36, and 25.60%, respectively. In summer (33.33%), the prevalence of V. parahaemolyticus was more common than that detected in the winter (14.01%). In addition, we identified 98 V. parahaemolyticus strains. The antimicrobial resistance trends of our seafood isolates to 15 antimicrobial agents revealed that major isolates were resistant to ampicillin (79.59%). Furthermore, 68.38% of the isolates were identified as being multidrug resistance. The prevalence of tdh or trh genes among the isolates was 8.16 and 12.24%, respectively. ERIC-PCR and multilocus sequence typing (MLST) results enabled classification of the isolates (n = 98) into different clusters, revealing genetic variation and relatedness among the isolates. Thus, our findings demonstrate the prevalence of V. parahaemolyticus in a variety of common seafood consumed domestically in China and provides insights into the dissemination of antibiotic-resistant strains, which should improve our microbiological risk assessment knowledge associated with V. parahaemolyticus in seafoods.

Virulence and Antibiotic Resistance of Vibrio parahaemolyticus Isolates from Seafood from Three Developing Countries and of Worldwide Environmental, Seafood, and Clinical Isolates from 2000 to 2017

Vibrio parahaemolyticus is a leading cause of seafood-associated illness. This study investigated the prevalence, virulence, and antibiotic resistance of V. parahaemolyticus in three low- and middle-income countries. Freshly caught fish samples (n = 330) imported to Jordan from Yemen, India, and Egypt were tested. The overall prevalence of V. parahaemolyticus was 15% (95% confidence interval: 11 to 19%). Three isolates (6%) were positive for the thermostable direct hemolysin-related (trh) gene, and all isolates was negative for the thermostable direct hemolysin (tdh) gene. All isolates were resistant to colistin sulfate, neomycin, and kanamycin, and 51 and 43% of isolates were resistant to tetracycline and ampicillin, respectively. Only 4% of the isolates were resistant to cefotaxime and chloramphenicol, and no isolates were resistant to sulfamethoxazole-trimethoprim, streptomycin, gentamicin, ciprofloxacin, and nalidixic acid. All isolates were resistant to two classes of antibiotics, and 86% were multidrug resistant (resistant to at least one drug in three or more classes of antibiotics). A literature review of clinical, seafood, and environmental V. parahaemolyticus isolates worldwide revealed high rates of gentamicin and ampicillin resistance, emerging resistance to third-generation cephalosporins, and limited resistance to sulfamethoxazole-trimethoprim, ciprofloxacin, nalidixic acid, and chloramphenicol. Thus, last-resort antibiotics could be ineffective for treating V. parahaemolyticus infections. Several global reports also documented illness outbreaks in humans caused by trh- and tdh-negative V. parahaemolyticus strains. More research is needed to determine whether the presence of these genes is sufficient to classify the strains as virulent.

Delineating the Origins of Vibrio parahaemolyticus Isolated from Outbreaks of Acute Hepatopancreatic Necrosis Disease in Asia by the Use of Whole Genome Sequencing

Acute hepatopancreatic necrosis disease (AHPND) is an emerging penaeid shrimp disease caused by Vibrio parahaemolyticus. Although V. parahaemolyticus has been isolated and sequenced from several Asia countries, the epidemiological links among the AHPND outbreaks in different locations remain unclear. In this study, we sequenced the genomes of nine strains isolated in China between 2014 and 2016 from four sampling sites in three provinces. Analysis of single nucleotide polymorphisms (SNPs) among the nine isolates yielded an average of 35,519 SNPs per isolate, ranging from 35,001 SNPs to 35,889 SNPs relative to the reference genome FDA_R31. To capture the genetic diversity of V. parahaemolyticus in Asia and Mexico, 93 published genomes were included in the analysis. Phylogenetic analysis divided the 102 isolates into 5 clades from I to V, with the majority belonging to Clade I and Clade II. There were at least 12 independent AHPND related clones. The results indicated that the clones recovered from AHPND affected shrimps in Asia were genomically distinct in various locations and there are no epidemiological links between Asian and Mexico outbreaks. Core genome analysis of pVA-1-like plasmid sequences from V. parahaemolyticus revealed that the AHPND-associated plasmids were also genetically diverse. Homology analysis of the publicly available microbial genomes showed that the conjugative transfer gene clusters of the plasmids in AHPND-causing strains were found in 27 V. parahaemolyticus strains and several other Vibrio sp. from 10 countries including five strains isolated prior to the first identification of AHPND outbreak, indicating that the backbone of AHPND- associated plasmid was widely distributed around the globe. In conclusion, at least 11 origins of AHPND outbreaks were identified; as AHPND-causing plasmid is widely distributed globally, prevention strategies for AHPND need to focus on microbial management in the aquaculture system and establishing ecological friendly aquaculture practices instead of detection of plasmid alone. However, more strains from other Asia countries as well as Mexico need to be included for whole genome sequencing (WGS) for reconstruction of the global transmission and the spread patterns of AHPND.

A Comprehensive Epidemiological Research for Clinical Vibrio parahaemolyticus in Shanghai

Vibrio parahaemolyticus is one of the most important pathogen for seafood-borne gastroenteritis in Shanghai and the rest of the world. A total of 42 V. parahaemolyticus strains were isolated from 1900 fecal specimens collected from patients in Shanghai hospital presenting from January 2014 to December 2015. All isolates were evaluated for potential virulence factors [tdh, trh, and type three secretion system (T3SS) genes], typed using multilocus sequence typing (MLST) and screened for antimicrobial resistance phenotype and genotype. And for the first time, the relationship between virulence, genetic diversity and antimicrobial resistance of these isolates were identified. The results showed that 37 isolates carried the tdh gene (88.1%) and only seven isolates were positive for the trh gene. The T3SS1 and T3SS2 genes were detected in all strains and only trh-positive isolates are also containing the T3SS2β genes. MLST analysis of the 42 Shanghai isolates identified 20 sequence types (STs) with 16 novel STs and that these clinical V. parahaemolyticus strains showed high degrees of genetic diversity. All isolates expressed high levels of resistance against Ampicillin (100.0%), Streptomycin (100.0%), Cephazolin (92.9%), Kanamycin (92.8%) and Amikacin (90.5%), and eight out of 38 resistance genes (SHV, tet(B), strA, qnrA, gryA, qnrB, sulI, sulII) were detected in at least two isolates. This study confirms that antimicrobial resistance of clinical V. parahaemolyticus isolates is greater than those of environmental isolates. Furthermore, no clear correlation between antimicrobial resistance and virulence or genetic diversity was found in this study. These results add to epidemiological data of clinical V. parahaemolyticus isolates in Shanghai and highlight the need for additional mechanistic studies, especially antimicrobial resistance, to reduce the burden of disease caused by this pathogen in China.