Antimicrobial resistance and potential virulence of Vibrio parahaemolyticus isolated from water and bivalve mollusks from Bahia, Brazil

Unveiling the positive impact of biofloc culture on Vibrio parahaemolyticus infection of Pacific white shrimp by reducing quorum sensing and virulence gene expression and enhancing immunity

This study aimed to evaluate and unveil the positive impact of biofloc culture on Vibrio parahaemolyticus infection of Pacific white shrimp by reducing quorum sensing (QS) and virulence gene expression and enhancing shrimp's immunity. The shrimp with an average body weight of 0.50 ± 0.09 g were reared in containers with a volume of 2.5 L, 21 units, and a density of 20 shrimp L-1. The shrimp were cultured for 5 days, with each treatment including biofloc system maintenance with a C/N ratio of 10 and a control treatment without biofloc, followed by a challenge test through immersion using V. parahaemolyticus at densities of 103, 105, and 107 CFU mL-1 initially. The results of the in vitro experiment showed that biofloc suspension can inhibit and disperse biofilm formation, as well as reduce the exo-enzyme activity (amylase, protease, and chitinase) of V. parahaemolyticus. Furthermore, the biofloc treatment significantly reduced the expression of the QS regulatory gene OpaR, the PirB toxin gene, and the virulence factor genes T6SS1 and T6SS2 in both in vitro and in vivo. The biofloc system also increased the expression of shrimp immunity-related genes (LGBP, proPO, SP, and PE) and the survival rate of white shrimp challenged with V. parahaemolyticus.

Assessing the Microbial Quality of Shrimp (Xiphonaeus kroyeri) and Mussels (Perna perna) Illegally Sold in the Vitória Region, Brazil, and Investigating the Antimicrobial Resistance of Escherichia coli Isolates

The consumption of seafood is crucial for food security, but poor hygiene along the food production chain can result in low microbiological quality, posing significant risks for public health and seafood quality. Thus, this study aimed to assess the microbiological quality and antimicrobial sensitivity of E. coli from 69 samples of illegally marketed shrimp and mussels in the Vitória Region, Brazil. These foods exhibited poor microbiological quality due to high counts of mesophilic, psychrotrophic, and enterobacteria microorganisms. While this issue is widespread in this area, shrimp samples displayed higher microbial counts compared to mussels, and fresh mussels had elevated counts of enterobacteria compared to frozen ones. Among the 10 E. coli isolates, none carried the genes blaCTX-M-1, blaCTX-M-2, blaCTX-M-3, blaCTX-M-15, mcr-1, mcr-2, mcr-3, mcr-4, and tet, associated with antibiotic resistance. Phenotypical resistance to tetracycline and fosfomycin was not observed in any isolate, while only 20% demonstrated resistance to ciprofloxacin. Regarding ampicillin and amoxicillin with clavulanic acid, 60% of isolates were resistant, 10% showed intermediate susceptibility, and 30% were sensitive. One isolate was considered simultaneously resistant to β-lactams and quinolones, and none were conserved as ESBL producers. These findings highlight the inherent risks to local public health that arise from consuming improperly prepared seafood in this area.

Tracking antimicrobial resistance indicator genes in wild flatfish from the English Channel and the North Sea area: A one health concern

Antimicrobial resistance (AMR) is a burgeoning environmental concern demanding a comprehensive One Health investigation to thwart its transmission to animals and humans, ensuring food safety. Seafood, housing bacterial AMR, poses a direct threat to consumer health, amplifying the risk of hospitalization, invasive infections, and death due to compromised antimicrobial treatments. The associated antimicrobial resistance genes (ARGs) in diverse marine species can amass and transmit through various pathways, including surface contact, respiration, and feeding within food webs. Our research, focused on the English Channel and North Sea, pivotal economic areas, specifically explores the occurrence of four proposed AMR indicator genes (tet(A), blaTEM, sul1, and intI1) in a benthic food web. Analyzing 350 flatfish samples' skin, gills, and gut, our quantitative PCR (qPCR) results disclosed an overall prevalence of 71.4% for AMR indicator genes. Notably, sul1 and intI1 genes exhibited higher detection in fish skin, reaching a prevalence of 47.5%, compared to gills and gut samples. Proximity to major European ports (Le Havre, Dunkirk, Rotterdam) correlated with increased AMR gene frequencies in fish, suggesting these ports' potential role in AMR spread in marine environments. We observed a broad dispersion of indicator genes in the English Channel and the North Sea, influenced by sea currents, maritime traffic, and flatfish movements. In conclusion, sul1 and intI1 genes emerge as robust indicators of AMR contamination in the marine environment, evident in seawater and species representing a benthic food web. Further studies are imperative to delineate marine species' role in accumulating and transmitting AMR to humans via seafood consumption. This research sheds light on the urgent need for a concerted effort in comprehending and mitigating AMR risks in marine ecosystems within the context of One Health.

Dynamics of efflux pumps in antimicrobial resistance, persistence, and community living of Vibrionaceae

The marine bacteria of the Vibrionaceae family are significant from the point of view of their role in the marine geochemical cycle, as well as symbionts and opportunistic pathogens of aquatic animals and humans. The well-known pathogens of this group, Vibrio cholerae, V. parahaemolyticus, and V. vulnificus, are responsible for significant morbidity and mortality associated with a range of infections from gastroenteritis to bacteremia acquired through the consumption of raw or undercooked seafood and exposure to seawater containing these pathogens. Although generally regarded as susceptible to commonly employed antibiotics, the antimicrobial resistance of Vibrio spp. has been on the rise in the last two decades, which has raised concern about future infections by these bacteria becoming increasingly challenging to treat. Diverse mechanisms of antimicrobial resistance have been discovered in pathogenic vibrios, the most important being the membrane efflux pumps, which contribute to antimicrobial resistance and their virulence, environmental fitness, and persistence through biofilm formation and quorum sensing. In this review, we discuss the evolution of antimicrobial resistance in pathogenic vibrios and some of the well-characterized efflux pumps' contributions to the physiology of antimicrobial resistance, host and environment survival, and their pathogenicity.

Antimicrobial resistance and antagonistic features of bivalve-associated Vibrio parahaemolyticus from the south-west coast of India

Vibrio parahaemolyticus, a potent human and aquatic pathogen, is usually found in estuaries and oceans. Human illness is associated with consuming uncooked/partially cooked contaminated seafood. The study on bivalve-associated V. parahaemolyticus revealed that the post-monsoon season had the highest bacterial abundance (9 ± 1.5 log cfu) compared to the monsoon season (8.03 ± 0.56 log cfu). Antimicrobial resistance (AMR) profiling was performed on 114 V. parahaemolyticus isolates obtained from bivalves. The highest AMR was observed against ampicillin (78%). Chloramphenicol was found to be effective against all the isolates. Multiple antibiotic resistance index values of 0.2 or higher were detected in 18% of the isolates. Molecular analysis of antimicrobial resistant genes (ARGs) revealed the high prevalence (100%) of the TEM-1 gene in the aquatic environment. After plasmid profiling and curing, 41.6% and 100% of the resistant isolates were found to be sensitive to ampicillin and cephalosporins, respectively, indicating the prevalence of plasmid-associated ARGs in the aquatic environment. A study to evaluate the antagonistic properties of Bacillus subtilis, Pseudomonas aeruginosa, and Bacillus amyloliquefaciens against V. parahaemolyticus isolates identified the potential of these bacteria to resist the growth of V. parahaemolyticus.

Trend of Pathogenic Vibrio parahaemolyticus Occurrences in Bivalve Molluscs Harvested in Sardinian Coastal Environments Between 2011 and 2018

The aim of the present study was to evaluate Vibrio parahaemolyticus occurrences in bivalve molluscs harvested from Sardinian coastal environments between 2013 and 2015. The prevalence of pathogenic V. parahaemolyticus isolates is based on the detection of the two major virulence genes thermostable direct hemolysin (tdh) and thermolabile hemolysin (trh) To assess changes between 2011 and 2018 in the prevalence of V. parahaemolyticus in bivalve molluscs, we compared our results with those of previous investigations. In total, 2,933 samples were collected: 1,079 in 2013, 1,288 in 2014, and 566 in 2015. The mean prevalence of V. parahaemolyticus in shellfish was 3.5% in 2013, 1.7% in 2014, and 3.5% in 2015. The highest percentage of positive samples in 2013 and 2014 was observed in clams (3.5% and 2.7%, respectively), whereas in 2015, it was reported in oysters (15.1%). By comparing the sampling period of 2011-2014 with that of 2015-2018, an increase in the prevalence of V. parahaemolyticus was observed in shellfish (p < 0.05). In parallel, 208 potentially enteropathogenic V. parahaemolyticus strains were identified through the years 2011-2018 and, in particular, 10 trh+ and six tdh+ isolates. Our present study provides information regarding trends of V. parahaemolyticus occurrences in bivalve molluscs harvested from Sardinian coastal environments between 2011 and 2018 suggesting that the prevalence varies depending on the sampling period and shellfish species.

Occurrence and Molecular Characterization of Potentially Pathogenic Vibrio spp. in Seafood Collected in Sicily

Seafood can vehiculate foodborne illnesses from water to humans. Climate changes, increasing water contamination and coastlines anthropization, favor the global spread of Vibrio spp. and the occurrence of antibiotic-resistant isolates. The aim of this study was to evaluate the spread of potentially pathogenic Vibrio spp. in fishery products collected in Sicily and to assess their antibiotic resistance. Bacteriological and molecular methods were applied to 603 seafood samples to detect V. parahaemolyticus, V. cholerae, V. vulnificus, and Vibrio alginolyticus in order to assess their pathogenicity and antimicrobial resistance. About 30% of bivalves and 20% of other fishery products were contaminated by Vibrio spp.; V. parahaemolyticus accounted for 43/165 isolates, 3 of which were carrying either tdh or trh; V. cholerae accounted for 12/165 isolates, all of them non-O1 non-O139 and none carrying virulence genes; and V. vulnificus accounted for 5/165 isolates. The highest rates of resistance were observed for ampicillin, but we also detected strains resistant to antibiotics currently included among the most efficient against Vibrio spp. In spite of their current low incidence, their rise might pose further issues in treating infections; hence, these results stress the need for a continuous monitoring of antimicrobial resistance among fishery products and an effective risk assessment.

A systematic review and meta-analysis on antimicrobial resistance in marine bivalves

Bivalves are filter-feeding animals able to accumulate contaminants and microorganisms, either of marine or terrestrial origin. The aim of this study was to describe the prevalence of antimicrobial resistance (AMR) in bacterial isolates from bivalves using a systematic review of the literature. Comprehensive searches of MEDLINE, EMBASE, and Web of Science were carried out, based upon a registered protocol (PROSPERO), and following the preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines. The methodological quality of the included studies was assessed using a modified Hoy checklist. Meta-analyses of prevalence were carried out using random-effects models. In total, 103 articles were selected from 1,280 records and were included in the final analysis. The studies were from Asia (n = 54), Europe (n = 27), South and North America (n = 10 and n = 6, respectively), Africa (n = 2), Oceania (n = 1), and multicentre and intercontinental (n = 3). The meta-analysis of multiple antibiotic resistance (MAR) index revealed Aeromonas spp. as the genus with the highest prevalence of AMR (37%), followed by Vibrio spp. (34%), Salmonella spp. (18%), and Escherichia coli (15%). Resistance to third/fourth/fifth generation cephalosporins and fluoroquinolones, two highest priority, critically important antimicrobials (HPCIA), was recorded in approximately 10% of E. coli isolates. Resistance to carbapenems was very low (<2%) in Salmonella spp. and in E. coli, but was found in 5% of Vibrio spp. and in more than a third of Aeromonas spp. isolates. In aquatic bacteria, resistance to carbapenems was higher in Asian than in European isolates. Our study shows the presence of antibiotic resistant bacteria (ARB), including bacteria resistant to HPCIA, in marine bivalves, posing a risk for consumers.

Rapid and Visual Detection of Vibrio parahaemolyticus in Aquatic Foods Using blaCARB-17 Gene-Based Loop-Mediated Isothermal Amplification with Lateral Flow Dipstick (LAMP-LFD)

Vibrio parahaemolyticus is recognized as one of the most important foodborne pathogens responsible for gastroenteritis in humans. The bla_CARB-17 gene is an intrinsic β-lactamase gene and a novel species-specific genetic marker of V. parahaemolyticus. In this study, a loop-mediated isothermal amplification (LAMP) assay combined with a lateral flow dipstick (LFD) was developed targeting this bla_CARB-17 gene. The specificity of LAMP-LFD was ascertained by detecting V. parahaemolyticus ATCC 17802 and seven other non-V. parahaemolyticus strains. Finally, the practicability of LAMP-LFD was confirmed by detection with V. parahaemolyticus-contaminated samples and natural food samples. The results showed that the optimized reaction parameters of LAMP are as follows: 2.4 mmol/l Mg²⁺, 0.96 mmol/l dNTPs, 4.8 U Bst DNA polymerase, and an 8:1 ratio of inner primer to outer primer, at 63°C for 40 min. The optimized reaction time of the LFD assay is 60 min. Cross-reactivity analysis with the seven non-V. parahaemolyticus strains showed that LAMP-LFD was exclusively specific for V. parahaemolyticus. The detection limit of LAMP-LFD for V. parahaemolyticus genomic DNA was 2.1 × 10^-4 ng/μl, corresponding to 630 fg/reaction and displaying a sensitivity that is 100-fold higher than that of conventional PCR. LAMP-LFD in a spiking study revealed a detection limit of approximately 6 CFU/ml, which was similar with conventional PCR. The developed LAMP-LFD specifically identified the 10 V. parahaemolyticus isolates from 30 seafood samples, suggesting that this LAMP-LFD may be a suitable diagnostic method for detecting V. parahaemolyticus in aquatic foods.

Increased incidence and antimicrobial resistance among Vibrio parahaemolyticus in shellfishes from major fish markets in Cochin, South India: Seafood risk assessment

India remains as a top supplier of value-added seafoods to the global markets. Cochin is one of the leading fishing ports in India contributing to country’s major seafood export. As part of risk assessment, we analyzed the prevalence of multi-drug resistant Vibrio parahaemolyticus; seafood borne gastroenteritis-causing pathogen, in shellfishes collected from major fish markets in Cochin. This bacterial species was initially isolated on Thiosulfate-citrate-bile salts-sucrose agar and HiCrome™ Vibrio agar, further confirmed by detection of V. parahaemolyticus species-specific toxR gene and by 16S r RNA sequencing. A total of 113 confirmed V. parahaemolyticus were recovered. Almost all the strains exhibited resistance towards three or more antibiotics (multiple-drug resistant) and harbored virulence related exoenzymes especially hemolysin (Kanagawa phenomenon); which is indeed a matter of concern. The multiple antibiotic resistance (MAR) index of the isolates ranged from 0.21 to 0.57. Furthermore, our results also indicate a substantial increase in the incidence of the pathogen in seafood from the area compared to previous years. This may pose a risk to the local and international consumers of the seafood. Practicing complete hygiene and adequate cooking is strongly recommended. Regular monitoring of aquaculture areas and fish markets is urged to reduce dissemination of pathogenic V. parahaemolyticus in seafood and to prevent fatal cases of human infection induced by this species in the country.

Molecular and pathogenic characterization of Vibrio parahaemolyticus isolated from seafood

Gastroenteritis infections in humans are mainly associated with consumption of Vibrio parahaemolyticus contaminated shellfish, which causes health and economic loss. Virulence factor production, antibiotic resistance profile, and biofilm-forming capacity of Vibrio parahaemolyticus isolates on food and food contact surfaces at 30 °C were investigated to evaluate the antibiotic sensitivity and pathogenic level. Strains of V. parahaemolyticus were isolated from shellfish (e.g., Crassostrea gigas, Venerupis philippinarum, Mytilus coruscus, Anadara kagoshimensis) in Korea. When examined for 17 virulence factor-encoding genes, 53.3, 73.1, 87.1, 87.9, and 90.9% of the isolates were positive for genes encoding TDH, T6SS, T3SS1, T3SS2, and Type I pilus, respectively. All isolates showed resistance to vancomycin, tetracyclines, penicillin, nalidixic acid, and doxycycline, among 26 antibiotics tested, with most isolates resistant to kanamycin (93.5%), ampicillin (96.8%), clindamycin (96.8%), tobramycin (88.7%), amikacin (83.97%), and minocycline (80.7%). Biofilm formation, cell-cell attachment, and motility were high in most isolates. These findings may assist in monitoring the epidemics of the pathogen. Continuous monitoring could help to decrease V. parahaemolyticus infections and improve seafood safety.

Distribution and antimicrobial resistance of Vibrio parahaemolyticus isolated from fish and shrimp aquaculture farms along the Korean coast

The present study investigated the distribution and antimicrobial susceptibility patterns of Vibrio parahaemolyticus in water samples and aquatic animals (fish and shrimp) from major aquaculture farms along the Korean coast in 2018. V. parahaemolyticus is the most common pathogen causing seafood-borne illness. The strain was detected in 34.7% of all samples tested, and was detected at higher levels during summer to autumn when the water temperature is higher. Although more than 90.0% of V. parahaemolyticus isolates were sensitive to 13 of the 15 antimicrobials tested, which is useful for treating V. parahaemolyticus infectious disease, the isolates exhibited higher resistance to two antibiotics (colistin and ampicillin), which should be excluded as treatment options for these infections. Koreans typically enjoy consuming raw seafood. To reduce the potential human health risk of raw seafood consumption, the prevalence and antimicrobial resistance of V. parahaemolyticus in aquaculture environments should be continuously valuated.

Analysis of the antimicrobial resistance gene frequency in whole-genome sequenced Vibrio from Latin American countries

Vibrio species are important environmental-related bacteria responsible for diverse infections in humans due to consumption of contaminated water and seafood in underdeveloped areas of the world. This study aimed to investigate the frequency of antimicrobial resistance genes in 577 sequenced Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus strains isolated in Latin American countries available at the NCBI Pathogen Detection database and to determine the sequence type (ST) of the strains. Almost all strains studied (99.8%) carried at least one antimicrobial resistance gene, while 54.2 % presented a multidrug-resistance profile. The Vibrio strains exhibited genotypic resistance to 11 antimicrobial classes and almG, varG, and catB9, which confer resistance to antibiotic peptides, β-lactams and amphenicols, respectively, were the most detected genes. Vibrio parahaemolyticus and V. vulnificus showed a broad diversity of STs. Vibrio cholerae strains isolated in Haiti after 2010's earthquake presented the highest diversity and amount of resistance genes in the set of strains analysed and mostly belonged to ST69. In conclusion, the detection of resistance genes from 11 antimicrobial classes and the high number of multidrug-resistant Vibrio species strains emphasize that Latin American public health authorities should employ more efficient control measures and that special attention should be given for the rational use of antimicrobials in human therapy and aquaculture, since the consumption of contaminated water and seafood with resistant Vibrio may result in human infections difficult to be treated.

Presence, Seasonal Distribution, and Biomolecular Characterization of Vibrio parahaemolyticus and Vibrio vulnificus in Shellfish Harvested and Marketed in Sardinia (Italy) between 2017 and 2018

ABSTRACT

In the present study, we investigated the presence, seasonal distribution, and biomolecular characteristics of Vibrio parahaemolyticus and Vibrio vulnificus in samples of bivalve mollusks (Mytilus galloprovincialis, Crassostrea gigas, and Ruditapes decussatus) harvested and marketed in Sardinia (Italy) between 2017 and 2018. A total of 435 samples were submitted for qualitative determination of Vibrio spp., V. parahaemolyticus, and V. vulnificus. Potentially enteropathogenic isolates were detected with biomolecular methods. The overall prevalence of Vibrio spp. was 7.6%. The highest Vibrio prevalence was found in R. decussatus (8.3%). The prevalences of V. parahaemolyticus and V. vulnificus were 2.7 and 4.8%, respectively. Higher prevalences of V. parahaemolyticus and V. vulnificus were found in R. decussatus (4.2%) and C. gigas (6.2%), respectively. Only two pathogenic V. parahaemolyticus strains were recovered (genotypes: tdh- and trh+; tdh+ and trh-), both from M. galloprovincialis. None of the isolates were tdh+ and trh+. Pathogenic Vibrio infections are often underestimated, and human infections are increasing in Europe. European data on the true distribution of Vibrionaceae are scarce, and the results of the present study highlight the need of constant monitoring to update the distribution of pathogenic vibrios.

HIGHLIGHTS

Environmental parameters associated with incidence and transmission of pathogenic Vibrio spp

Vibrio spp. thrive in warm water and moderate salinity, and they are associated with aquatic invertebrates, notably crustaceans and zooplankton. At least 12 Vibrio spp. are known to cause infection in humans, and Vibrio cholerae is well documented as the etiological agent of pandemic cholera. Pathogenic non-cholera Vibrio spp., e.g., Vibrio parahaemolyticus and Vibrio vulnificus, cause gastroenteritis, septicemia, and other extra-intestinal infections. Incidence of vibriosis is rising globally, with evidence that anthropogenic factors, primarily emissions of carbon dioxide associated with atmospheric warming and more frequent and intense heatwaves, significantly influence environmental parameters, e.g., temperature, salinity, and nutrients, all of which can enhance growth of Vibrio spp. in aquatic ecosystems. It is not possible to eliminate Vibrio spp., as they are autochthonous to the aquatic environment and many play a critical role in carbon and nitrogen cycling. Risk prediction models provide an early warning that is essential for safeguarding public health. This is especially important for regions of the world vulnerable to infrastructure instability, including lack of 'water, sanitation, and hygiene' (WASH), and a less resilient infrastructure that is vulnerable to natural calamity, e.g., hurricanes, floods, and earthquakes, and/or social disruption and civil unrest, arising from war, coups, political crisis, and economic recession. Incorporating environmental, social, and behavioural parameters into such models allows improved prediction, particularly of cholera epidemics. We have reported that damage to WASH infrastructure, coupled with elevated air temperatures and followed by above average rainfall, promotes exposure of a population to contaminated water and increases the risk of an outbreak of cholera. Interestingly, global predictive risk models successful for cholera have the potential, with modification, to predict diseases caused by other clinically relevant Vibrio spp. In the research reported here, the focus was on environmental parameters associated with incidence and distribution of clinically relevant Vibrio spp. and their role in disease transmission. In addition, molecular methods designed for detection and enumeration proved useful for predictive modelling and are described, namely in the context of prediction of environmental conditions favourable to Vibrio spp., hence human health risk.

Occurrence and antibiogram signatures of some Vibrio species recovered from selected rivers in South West Nigeria

Vibrio species, widely distributed in water environments, has emerged as a prominent cause of water and food-related disease outbreaks posing significant risk to human and animal health worldwide. About 40% of presumptive isolates recovered from four selected rivers in Southwest Nigeria and, established as Vibrio species genus through polymerase chain reaction techniques., were subjected to antibiotic susceptibility testing against a panel of 18 commonly used antibiotics. The relative prevalence of key Vibrio species (V. parahaemolyticus, V. vulnificus, V. mimicus, V. harveyi, and V. cholerae) was in the order 17%, 13.3%, 4.4%, 2.2%, and 2.2% respectively. Antibiotic resistance by all Vibrio species was mostly observed against doxycycline (71-89%), erythromycin (86-100%), tetracycline (71-89%), rifampicin (86-100%), and sulfamethoxazole (87-100%), though susceptibility to meropenem (86-100%), cephalothin (60-100%), norfloxacin (93-100%), ciprofloxacin (88-100%), amikacin (64-100%), gentamicin (57-74%), and trimethoprim/sulfamethoxazole (57-81%) was equally observed in all species. Vibrio mimicus expressed highest resistance against streptomycin and chloramphenicol (64%), while V. vulnificus (52%) and V. cholerae (57%) had the highest resistance against cephalothin. High resistance against ampicillin (57%) and amoxicillin (50%) was exhibited by V. cholerae and V. mimicus respectively. Indexes of multiple antibiotic resistances (MARI) among Vibrio species ranged between 0.11 and 0.72 with the highest MAR index of 0.72 observed in one isolate of V. vulnificus. This study reveals high prevalence of Vibrio species in the selected rivers as well as elevated resistance against some first-line antibiotics, which suggests possible inappropriate antimicrobial usage around study communities. We conclude that the freshwater resources investigated are unfit for domestic, industrial, and recreational uses without treatment prior to use and are potential reservoirs of antibiotic-resistant Vibrio species in this environment.

Distribution of phenotypic and genotypic antimicrobial resistance and virulence genes in Vibrio parahaemolyticus isolated from cultivated oysters and estuarine water

A total of 594 Vibrio parahaemolyticus isolates from cultivated oysters (n = 361) and estuarine water (n = 233) were examined for antimicrobial resistance (AMR) phenotype and genotype and virulence genes. Four hundred forty isolates (74.1%) exhibited resistance to at least one antimicrobial agent and 13.5% of the isolates were multidrug-resistant strains. Most of the V. parahaemolyticus isolates were resistant to erythromycin (54.2%), followed by sulfamethoxazole (34.7%) and trimethoprim (27.9%). The most common resistance genes were qnr (77.8%), strB (27.4%) and tet(A) (22.1%), whereas blaTEM (0.8%) was rarely found. Four isolates (0.7%) from oysters (n = 2) and estuarine water (n = 2) were positive to tdh, whereas no trh-positive isolates were observed. Significantly positive associations among AMR genes were observed. The SXT elements and class 1, 2 and 3 integrons were absent in all isolates. The results indicated that V. parahaemolyticus isolates from oysters and estuarine water were potential reservoirs of resistance determinants in the environment. This increasing threat of resistant bacteria in the environment potentially affects human health. A 'One Health' approach involved in multidisciplinary collaborations must be implemented to effectively manage antimicrobial resistance.

Tropical shrimp aquaculture farms harbour pathogenic Vibrio parahaemolyticus with high genetic diversity and Carbapenam resistance

In characterization of food borne pathogens from the environment, assessment of virulence, genetic diversity and AMR are essential preludes to formulate preventive strategies and to combat the spread. This study aimed to identify and characterize pathogenic Vibrio parahaemolyticus in the coastal aquaculture farms of Kerala, India. Twenty-seven β-haemolytic V. parahaemolyticus were isolated from 7 out of 40 farms studied. Among the 27 isolates, 15 possessed the tdh gene and 4 had trh. ERIC PCR and PFGE illustrated the presence of pathogenic isolates that shared genetic similarity with clinical strains. One pathogenic isolate was identified to be multidrug resistant (MDR) and 59% exhibited a MAR index of 0.2 or above. Seventy four percent of the pathogenic isolates were ESBL producers and 3.7% of them were carbapenemase producers phenotypically. This asks for adoption of control measures during farming to prevent the transmission of pathogenic V. parahaemolyticus to the environment and food chain.

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.

Prevalence and genetic diversity of Vibrio parahaemolyticus strains from salmon in Chinese markets

Consumption of contaminated salmon in China has led to pathogenic Vibrio parahaemolyticus infections in humans. In this study, 420 salmon samples were collected from supermarkets and restaurants in China that showed a contamination rate of 9.05 and 15.24%, respectively. Eighteen antibiotics were used to test the antibiotic susceptibility of all 51 isolates. The most common resistance was observed to β-lactam antibiotics and aminoglycosides, including ampicillin (92.16%), streptomycin (88.24%), kanamycin (45.10%) and cephazolin (45.10%). Meanwhile, many strains were resistant to more than two antibiotics (48/51, 94.12%). Only two and five isolates were positive for tdh and trh, respectively. Serotyping results demonstrated that O2 was most prevalence serotype (15/51, 29.41%). Molecular typing (enterobacterial repetitive intergenic consensus sequence polymerase chain reaction and multilocus sequence typing) allowed classification of all the isolates into 5 clusters and 44 sequence types, highlighting genetic variation and relatedness. In general, the high antibiotic resistance is alarming and raises public health concerns. Frequent monitoring of salmon for V. parahaemolyticus contamination, genetic diversity and antibiotic susceptibility is essential to improve seafood safety.

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.

Antibacterial and antibiofilm mechanism of eugenol against antibiotic resistance Vibrio parahaemolyticus

The objective of this study was to investigate the antibacterial and antibiofilm activity of eugenol against V. parahaemolyticus planktonic and biofilm cells and the involved mechanisms as well. Atime-kill assay, a biofilm formation assay on the surface of crab shells, an assay to determine the reduction of virulence using eugenol at different concentrations, energy-filtered transmission electron microscope (EF-TEM), field emission scanning electron microscopy (FE-SEM), confocal laser scanning microscope (CLSM) and high-performance liquid chromatography (HPLC) were performed to evaluate the antibacterial and antibiofilm activity of eugenol. The results indicated that different concentrations of eugenol (0.1-0.6%) significantly reduced biofilm formation, metabolic activities, and secretion of extracellular polysaccharide (EPS), with effective antibacterial effect. Eugenol at 0.4% effectively eradicated the biofilms formed by clinical and environmental V. parahaemolyticus on crab surface by more than 4.5 and 4 log CFU/cm², respectively. At 0.6% concentration, the reduction rates of metabolic activities for ATCC27969 and NIFS29 were 79% and 68%, respectively. Whereas, the reduction rates of EPS for ATCC27969 and NIFS29 were 78% and 71%, respectively. On visual evaluation, significant results were observed for biofilm reduction, live/dead cell detection, and quorum sensing (QS). This study demonstrated that eugenol can be used to control V. parahaemolyticus biofilms and biofilm-related infections and can be employed for the protection of seafood.

Abundance, antimicrobial resistance, and virulence of pathogenic Vibrio strains from molluscan shellfish farms along the Korean coast

To reduce the outbreaks caused by the major pathogenic Vibrio species, V. parahaemolyticus, V. vulnificus, and V. cholerae, the distribution, antibiotic resistance, and virulence of these Vibrio strains were monitored in shellfish and seawater along the Korean coast. Among the Vibrio strains, V. parahaemolyticus was the most abundant species; during summer, this strain showed a substantial increase that correlated with the water temperature. Although >99.0% of the Vibrio species isolates were sensitive to seven antimicrobials recommended by the Center for Disease Control and Prevention for the treatment of Vibrio infections, multiple-antibiotic resistance to at least three antimicrobials was found in 14.3% to 50.0% of each Vibrio species. Among V. parahaemolyticus isolates, 14.3% were positive for the trh gene, whereas only 1% was positive for the tdh gene. These results should aid in implementing proper precautions to avoid potential human health risks associated with exposure to pathogenic Vibrio species.

Prevalence, Antibiotic-Resistance, and Virulence Characteristics of Vibrio parahaemolyticus in Restaurant Fish Tanks in Seoul, South Korea

Vibrio parahaemolyticus is a marine bacterium that causes foodborne diarrhea. Many seafood restaurants keep live fish and shellfish in fish tanks for use in raw seafood dishes; thus, the present study aimed to investigate the prevalence, antibiotic-resistance, and virulence characteristics exhibited by V. parahaemolyticus detected in restaurant fish-tank water samples collected in Seoul, South Korea. Fish-tank water samples were collected from 69 restaurants in Seoul, and screened for the presence of V. parahaemolyticus via both a commercial detection kit, and a real-time polymerase chain reaction (RT-PCR) to detect the toxR gene. Antibiotic susceptibility and virulence determinants of V. parahaemolyticus isolates were evaluated and identified using standard disk-diffusion and RT-PCR methods, respectively. Thirty-five (50.7%) of the 69 analyzed water samples were found to be contaminated with V. parahaemolyticus. Those isolates were most often resistant to ampicillin (51.4% of isolates), followed by amikacin and tetracycline (11.4%), and ceftazidime (8.6%). Thirty (85.7%) out of the 35 isolates carried all four cytotoxicity-inducing type III secretion system 1 (T3SS1) genes [specifically, 34 (97.1%), 33 (94.3%), 35 (100%), and 32 (91.4%) isolates carried genes encoding the VP1670, VP1686, VP1689, and VP1694 T3SS1 proteins, respectively]. The type VI secretion systems (T6SS1 and T6SS2) genes were also detected in 11 (31.4%) and 27 (77.1%) isolates, respectively. However, virulence determinants such as the hemolysin (tdh and trh), urease (ureC), T3SS2α, or T3SS2β genes that are known to be associated with enterotoxicity were not detected in all isolates. Although some known major virulence genes were not detected in the V. parahaemolyticus isolates, the results of this study indicate that restaurant fish tanks are a potential source of antibiotic-resistant V. parahaemolyticus. The presented data support the need for strict guidelines to regulate the maintenance of restaurant fish tanks to prevent antibiotic-resistant foodborne vibriosis.

Integrative and Conjugative Elements-Positive Vibrio parahaemolyticus Isolated From Aquaculture Shrimp in Jiangsu, China

The development of multidrug- and toxin-resistant bacteria as a result of increasing industrialization and sustained and intense antimicrobial use in aquaculture results in human health problems through increased incidence of food-borne illnesses. Integrative and conjugative elements (ICEs) are self-transmissible mobile genetic elements that allow bacteria to acquire complex new traits through horizontal gene transfer and encode a wide variety of genetic information, including resistance to antibiotics and heavy metals; however, there is a lack of studies of ICEs of environmental origin in Asia. Here, we determined the prevalence, genotypes, heavy metal resistance and antimicrobial susceptibility of 997 presumptive strains of Vibrio parahaemolyticus (tlh⁺, tdh^–), a Gram-negative bacterium that causes gastrointestinal illness in humans, isolated from four species of aquaculture shrimp in Jiangsu, China. We found that 59 of the 997 isolates (5.9%) were ICE-positive, and of these, 9 isolates tested positive for all resistance genes. BLAST analysis showed that similarity for the eight strains to V. parahaemolyticus was 99%. Tracing the V. parahaemolyticus genotypes, showed no significant relevance of genotype among the antimicrobial resistance strains bearing the ICEs or not. Thus, in aquaculture, ICEs are not the major transmission mediators of resistance to antibiotics or heavy metals. We suggest future research to elucidate mechanisms that drive transmission of resistance determinants in V. parahaemolyticus.

Occurrence, virulence, and antimicrobial resistance of Vibrio parahaemolyticus isolated from bivalve shellfish farms along the southern coast of Korea

Vibrio parahaemolyticus is the most common pathogen causing seafood-borne illnesses in Korea. The present study evaluated the occurrence, virulence, and antimicrobial resistance of V. parahaemolyticus in seawater and bivalves obtained in 2016 from the southern coast of Korea, an important region for commercial aquaculture industries, especially the Korean raw seafood culture. V. parahaemolyticus was detected in 87 of 160 (54.4%) bivalve samples and in 32 of 130 (24.5%) seawater samples. Especially high levels were detected during summer to early autumn. All the seawater and bivalves contained less than 2 and 5% of the tdh and trh genes of the isolates, respectively, and seawater isolates possessed two fewer genes than the bivalve isolates. Of 23 antimicrobials tested, three agents (ofloxacin, norfloxacin, and trimethoprim/sulfamethoxazole) effectively treated V. parahaemolyticus illness due to the sensitivity of the isolates. The isolates were highly resistant to ampicillin, however, excluding it as a treatment option. More than half of the isolates exhibited resistance to at least three antimicrobials. These findings indicate the importance of an integrated monitoring and surveillance program noting the occurrence, virulence, and antimicrobial resistance patterns of V. parahaemolyticus in various aquatic sources for preventing human health risks from seafood consumption.

Genetic Relationship, Virulence Factors, Drug Resistance Profile and Biofilm Formation Ability of Vibrio parahaemolyticus Isolated From Mussel

The objective of this study was to investigate the virulence factors, genetic relationship, antibiotic resistance profile and the biofilm formation ability of Vibrio parahaemolyticus isolates on shrimp and mussel surfaces at 30°C. In this study, eight (n = 8) V. parahaemolyticus isolated from mussel were examined. We used the polymerase chain reaction (PCR) to examine the distribution of different genes, and Repetitive Extragenic Palindromic-PCR (REP-PCR) to compare the genetic relationship. Disk diffusion technique was used to assess antibiotic and multiple-antibiotic resistance. The biofilm formation assay, and field emission scanning electron microscopy (FE-SEM) were used to evaluate biofilm formation ability. Transmission Electron Microscope (TEM) was used to observe the morphological structure of bacterial cell. Our results indicated that the biofilm-associated genes, 16S rRNA, toxR, and tdh, were present in all the tested V. parahaemolyticus isolates (n = 8). Approximately, 62.5% (5 isolates among 8 isolates) isolates showed strong multiple-antibiotic resistance index with an average value of 0.56. All isolates (n = 8) showed strong genetic relationship and significant biofilm formation ability on shrimp and mussel surfaces. This study demonstrated that the presence of virulence factors, high multiple antibiotic resistance index (MARI) values, and effective biofilm formation ability of V. parahaemolyticus isolates could be a great threat to human health and economic values in future. It was also suggested that a high resistance rate to antibiotic could be ineffective for treating V. parahaemolyticus infections. The continuous monitoring of V. parahaemolyticus antibiotic, molecular and biofilm characteristics is needed to increase seafood safety.