Molecular typing of Vibrio parahaemolyticus isolates from the middle-east coastline of China

Visual LAMP method for the detection of Vibrio vulnificus in aquatic products and environmental water

Background

A visual, rapid, simple method was developed based on a loop-mediated isothermal amplification (LAMP) assay to detect Vibrio vulnificus in aquatic products and aquaculture waters.

Results

Genomic DNA was extracted from Vibrio vulnificus using the boiling method, and optimized primers were used to detect the gyrB gene using a visual LAMP method. The sensitivity of the assay was 10 fg/μL, and the obtained results were stable and reliable. Out of 655 aquatic product samples and 558 aquaculture water samples, the positive rates of Vibrio vulnificus detection were 9.01% and 8.60%, respectively, which are markedly higher than those of the traditional culture identification methods.

Conclusion

The relatively simple technical requirements, low equipment cost, and rapid detection make the visual LAMP method for the detection of Vibrio vulnificus a convenient choice for field detection in the aquaculture industry.

Modulation of Intestinal Barrier, Inflammatory Response, and Gut Microbiota by Pediococcus pentosaceus zy-B Alleviates Vibrio parahaemolyticus Infection in C57BL/6J Mice

Modulation of the intestinal barrier, inflammation, and gut microbiota by Pediococcus pentosaceus zy-B (zy-B) in Vibrio parahaemolyticus (Vp)-infected C57BL/6J mice was studied. Mice intragastrically pretreated with 10⁸ colony-forming units (CFU) zy-B significantly alleviated Vp infection as evidenced by maintaining body weight and reduced disease activity index score and intestine ratio. In addition, zy-B reduced the Vp load in the ileum and cecum, significantly reduced the load in the colon, prevented colonic atrophy, and strengthened mucosal integrity. Mechanistically, zy-B ameliorated intestinal barrier dysfunction by upregulating tight junction protein expression, which in turn reduced the lipopolysaccharide, d-lactic acid (d-LA), and diamine oxidase concentrations and downregulated the cannabinoid receptor 1 (CB1) and CB2 mRNA expressions. Moreover, zy-B systemically reduced inflammation by decreasing interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α levels, and increased interleukin-10 (IL-10), immunoglobulin M (IgM), and immunoglobulin G (IgG) levels in the colon and serum. Furthermore, zy-B markedly altered the gut microbiota composition by enriching Bifidobacterium, Akkermansia, and Lactobacillus in the colon. Overall, zy-B appears to act as a probiotic to alleviate Vp infection by protecting the intestinal barrier, reducing inflammation, and promoting the growth of "beneficial" gut microbiota.

Genetic Diversity and Population Structure of Vibrio parahaemolyticus Isolated From Clinical and Food Sources

Vibrio parahaemolyticus is a common foodborne pathogen that causes gastroenteritis worldwide. Determining its prevalence and genetic diversity will minimize the risk of infection and the associated economic burden. Multilocus sequence typing (MLST) is an important tool for molecular epidemiology and population genetic studies of bacteria. Here, we analyzed the genetic and evolutionary relationships of 162 V. parahaemolyticus strains isolated in the Guangdong Province, China, using MLST. In the study, 120 strains were isolated from food samples, and 42 strains were isolated from clinical samples. All strains were categorized into 100 sequence types (STs), of which 58 were novel (48 from the food isolates and 10 from the clinical isolates). ST415 was the most prevalent ST among the food isolates, while ST3 was the most prevalent ST among the clinical isolates. Further, 12 clonal complexes, 14 doublets, and 73 singletons were identified in all ST clusters, indicating high genetic diversity of the analyzed strains. At the concatenated sequence level, non-synonymous sites in both, food and clinical isolates, were associated with purifying selection. Of note, the dN/dS ration was greater than 1 for some housekeeping genes in all isolates. This is the first time that some loci under positive selection were identified. These observations confirm frequent recombination events in V. parahaemolyticus. Recombination was much more important than mutation for genetic heterogeneity of the food isolates, but the probabilities of recombination and mutations were almost equal for the clinical isolates. Based on the phylogenetic analysis, the clinical isolates were concentrated in the maximum-likelihood tree, while the food isolates were heterogeneously distributed. In conclusion, the food and clinical isolates of V. parahaemolyticus from the Guangdong Province are similar, but show different evolutionary trends. This may help prevent large-scale spread of highly virulent strains and provides a genetic basis for the discovery of microevolutionary relationships in V. parahaemolyticus populations.

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.

Vibrio harveyi isolated from marine aquaculture species in eastern China and virulence to the large yellow croaker (Larimichthys crocea)

AIMS

Diseases of maricultured species caused by Vibrio harveyi are increasing in China and other regions. This study examined the genetic diversity, antimicrobial susceptibility, plasmid profiles and virulence potential of the V. harveyi isolated from marine organisms farmed in two provinces in eastern China between 2014 and 2019.

METHODS AND RESULTS

A total of 54 V. harveyi were obtained from seven marine species. Enterobacterial repetitive intergenic consensus (ERIC)-PCR fingerprinting revealed substantial genetic heterogeneity among the V. harveyi isolates. There was no significant correlation between ERIC-PCR genotypes and host origins or fish farms. All the isolates were resistant to amoxicillin and ampicillin, and 79·6% to kanamycin. We found that 61·1% of the V. harveyi isolates had plasmid(s) and there were 14 different plasmid profiles. Most isolates from fish hosts (76·5%) contained plasmids; however, 75% of isolates from nonfish hosts lacked plasmids. Experimental infection results showed that isolates with plasmid(s) were more virulent to large yellow croaker than isolates lacking plasmids (P < 0·05).

CONCLUSIONS

This study confirmed that V. harveyi isolates obtained from animals farmed in the coastal region of east China were genetically diverse. Our results suggest that the virulence of various V. harveyi strains to fish is associated with the plasmids they carry.

SIGNIFICANCE AND IMPACT OF THE STUDY

More than 50% of the V. harveyi isolates carried one to 11 plasmids. The plasmid-borne traits of V. harveyi strains might be important for host adaptation and virulence, but they were not associated with susceptibility to the tested antibiotics.

Characterization of Pathogenic Vibrio parahaemolyticus Isolated From Fish Aquaculture of the Southwest Coastal Area of Bangladesh

Vibrio parahaemolyticus is a major foodborne pathogen responsible for significant economic losses in aquaculture and a threat to human health. Here, we explored the incidence, virulence potential, and diversity of V. parahaemolyticus isolates from aquaculture farms in Bangladesh. We examined a total of 216 water, sediment, Oreochromis niloticus (tilapia), Labeo rohita (rui), and Penaeus monodon (shrimp) samples from the aquaculture system where 60.2% (130/216) samples were positive for V. parahaemolyticus. Furthermore, we identified 323 V. parahaemolyticus strains from contaminated samples, 17 of which were found positive for trh, a virulence gene. Four isolates out of the 17 obtained were able to accumulate fluid in the rabbit ileal loop assay. The correlation between the contamination of V. parahaemolyticus and environmental factors was determined by Pearson correlation. The temperature and salinity were significantly correlated (positive) with the incidence of V. parahaemolyticus. Most of the pathogenic isolates (94.1%) were found resistant to ampicillin and amoxicillin. O8: KUT was the predominant serotype of the potentially pathogenic isolates. ERIC-PCR reveals genetic variation and relatedness among the pathogenic isolates. Therefore, this region-specific study establishes the incidence of potential infection with V. parahaemolyticus from the consumption of tilapia, rui, and shrimp raised in farms in Satkhira, Bangladesh, and the basis for developing strategies to reduce the risk for diseases and economic burden.

Community Structure of Protease-Producing Bacteria Cultivated From Aquaculture Systems: Potential Impact of a Tropical Environment

Protease-producing bacteria play vital roles in degrading organic matter of aquaculture system, while the knowledge of diversity and bacterial community structure of protease-producing bacteria is limited in this system, especially in the tropical region. Herein, 1,179 cultivable protease-producing bacterial strains that belonged to Actinobacteria, Firmicutes, and Proteobacteria were isolated from tropical aquaculture systems, of which the most abundant genus was Bacillus, followed by Vibrio. The diversity and relative abundance of protease-producing bacteria in sediment were generally higher than those in water. Twenty-one genera from sediment and 16 genera from water were identified, of which Bacillus dominated by Bacillus hwajinpoensis in both and Vibrio dominated by Vibrio owensii in water were the dominant genera. The unique genera in sediment or water accounted for tiny percentage may play important roles in the stability of community structure. Eighty V. owensii isolates were clustered into four clusters (ET-1-ET-4) at 58% of similarity by ERIC-PCR (enterobacterial repetitive intergenic consensus-polymerase chain reaction), which was identified as a novel branch of V. owensii. Additionally, V. owensii strains belonged to ET-3 and ET-4 were detected in most aquaculture ponds without outbreak of epidemics, indicating that these protease-producing bacteria may be used as potential beneficial bacteria for wastewater purification. Environmental variables played important roles in shaping protease-producing bacterial diversity and community structure in aquaculture systems. In sediment, dissolved oxygen (DO), chemical oxygen demand (COD), and salinity as the main factors positively affected the distributions of dominant genus (Vibrio) and unique genera (Planococcus and Psychrobacter), whereas temperature negatively affected that of Bacillus (except B. hwajinpoensis). In water, Alteromonas as unique genus and Photobacterium were negatively affected by NO₃ ^--N and NO₂ ^--N, respectively, whereas pH as the main factor positively affected the distribution of Photobacterium. These findings will lay a foundation for the development of protease-producing bacterial agents for wastewater purification and the construction of an environment-friendly tropical aquaculture model.

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.

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.

Genetic and virulence characterisation of Vibrio parahaemolyticus isolated from Indian coast

BACKGROUND

V. parahaemolyticus is autochthonous to the marine environment and causes seafood-borne gastroenteritis in humans. Generally, V. parahaemolyticus recovered from the environment and/or seafood is thought to be non-pathogenic and the relationship between environmental isolates and acute diarrhoeal disease is poorly understood. In this study, we explored the virulence potential of environmental V. parahaemolyticus isolated from water, plankton and assorted seafood samples collected from the Indian coast.

RESULTS

Twenty-two V. parahaemolyticus isolates from seafood harboured virulence associated genes encoding the thermostable-direct haemolysin (TDH), TDH-related haemolysin (TRH), and Type 3 secretion systems (T3SS) and 95.5% of the toxigenic isolates had pandemic strain attributes (toxRS/new+). Nine serovars, with pandemic strain traits were newly identified and an O4:K36 tdh-trh+V. parahaemolyticus bearing pandemic marker gene was recognised for the first time. Results obtained by reverse transcription PCR showed trh, T3SS1 and T3SS2β to be functional in the seafood isolates. Moreover, the environmental strains were cytotoxic and could invade Caco-2 cells upon infection as well as induce changes to the tight junction protein, ZO-1 and the actin cytoskeleton.

CONCLUSION

Our study provides evidence that environmental isolates of V. parahaemolyticus are potentially invasive and capable of eliciting pathogenic characteristics typical of clinical strains and present a potential health risk. We also demonstrate that virulence of this pathogen is highly complex and hence draws attention for the need to investigate more reliable virulence markers in order to distinguish the environmental and clinical isolates, which will be crucial for the pathogenomics and control of this pathogen.

Challenges in Vibrio parahaemolyticus infections caused by the pandemic clone

Vibrio Parahaemolyticus infections caused by the pandemic clone have become a global public health issue. The pandemic clone includes over ten sequence types and 49 serotypes. Several markers such as toxRS/new, orf8 and genomic islands were considered specific for pandemic strains, but subsequent studies later confirmed a lack of specificity. Thus, identifying stable indicators for the pandemic clone is still an open question. In recent years, several environmental pandemic strains are growing, constituting a new threat to seafood safety and human health. Traditional methods show limited discrimination in studying the microevolution of pandemic strains. For example, multilocus sequence typing divides many pandemic strains into ST3 type, making it difficult to further distinguish the variability within ST3 strains from different contexts. When using a whole genome sequencing-based technique, strains including those with the same sequence type, could be well separated. Whole genome sequencing-based technology also played important roles in dissecting the evolution process and revealing the mechanism underlying rapid serotype conversion within pandemic strains. In addition, the emergence of multiple-antibiotic resistant pandemic strains needs attention. Altogether, we are facing many challenges posed by pandemic V. parahaemolyticus strains, which need to be resolved in future studies.

Antimicrobial resistance and pulsed-field gel electrophoresis typing of Vibrio parahaemolyticus isolated from shrimp mariculture environment along the east coast of China

Environmental antimicrobial resistance (AMR) has drawn increasing attention due to its great risk to human health. The aim of this study was to investigate AMR and genotyping of Vibrio parahaemolyticus isolates (n = 114) recovered from shrimp mariculture environment in China. The isolates exhibited a high rate of resistance to streptomycin (78.9%), ampicillin (64.9%) and gentamicin (53.5%). Furthermore, multi-drug resistance was highly prevalent (61.4%), in which 95.9% of these ampicillin-resistant isolates were primarily mediated by bla_CARB-17. Surprisingly, doxycylcine, florfenicol, and trimethoprim/sulfamethoxazole (TMP/SMZ) resistance genes occurred in susceptible isolates. Moreover, 114 isolates were grouped into unique pulsed field gel electrophoresis patterns. These findings suggest the need for the prudent use of antimicrobial agents on mariculture farms, in order to control the dissemination of antimicrobial resistant V. parahaemolyticus.

Combination of Multilocus Sequence Typing and GS-PCR Reveals an Association of Pandemic Vibrio parahaemolyticus Clone with Clinical and Seafood Isolates

Vibrio parahaemolyticus is a global leading cause of seafood-borne bacterial gastroenteritis. Clinical, seafood, and environmental V. parahaemolyticus isolates from the eastern coast of China were analyzed for their virulence, and for phenotypic and molecular traits. The frequency of pandemic isolates was 50.9% among clinical isolates and 42.8% among seafood isolates as confirmed by group-specific polymerase chain reaction (GS-PCR). Serological analysis indicated that O3:K6, O1:K25, O1:KUT, O3:K68, and O4:K68 were the predominant serotypes among these pandemic isolates. It is worth noting that the pandemic serotypes were not exclusively identified from clinical samples. Rather, they were also isolated from seafood samples. It was also shown by multilocus sequence typing (MLST) typing that isolates from clinical (59), seafood (28), and environmental samples (18) were grouped into 17, 23, and 17 sequence types (STs), respectively. We updated 17 STs in the MLST database. ST-3 and ST-189 were the dominant ones among clinical isolates. Interestingly, ST-3 was also the most abundant among seafood isolates, and represented a significant risk to food safety due to the clear association with tdh and the GS-PCR marker. A minimum-evolution (ME) tree generated from the concatenated sequences of the 7 loci of the 54 STs uncovered phylogenetic relationships between seafood and clinical isolates. The MLST results also indicated a high degree of nucleotide diversity in recA that had the greatest influence on the phylogenetic relationships. Our findings provided new insight into the phylogenic relationship among pandemic V. parahaemolyticus isolates from various samples and enhanced the MLST database as well as microbiological risk assessment.

PRACTICAL APPLICATION

Pandemic V. parahaemolyticus isolates have become a serious public health concern. This study demonstrated the characteristics of clinical and seafood V. parahaemolyticus isolates, and determined the phylogenetic relatedness among them. These results can be used for microbiological risk assessment in China.

Antimicrobial Resistance, Virulence Factors, and Genetic Profiles of Vibrio parahaemolyticus from Seafood

Vibrio parahaemolyticus is a widespread bacterium in the marine environment and is responsible for gastroenteritis in humans. Foodborne infections are mainly associated with the consumption of contaminated raw or undercooked fish and shellfish. The aim of this study was to determine the antimicrobial resistance, virulence factors, and genetic profiles of V. parahaemolyticus isolates from seafood originating from different countries. A total of 104 (17.5%) isolates were recovered from 595 analyzed samples. The isolates were tested for the presence of the tdh and trh genes, involved in the pathogenesis of V. parahaemolyticus infections in humans, and these genes were detected in 3 (2.9%) and 11 (10.6%) isolates, respectively. The trh-positive isolates also possessed the ure gene, which is responsible for urease production. Moreover, the activity of protease A was identified in all V. parahaemolyticus strains. Antimicrobial resistance revealed that most isolates were resistant to ampicillin (75.0%) and streptomycin (68.3%), whereas all strains were sensitive to chloramphenicol and tetracyclines. Most of the isolates (55.8%) showed resistance against two classes of antimicrobials, mainly to ampicillin and streptomycin (46.2%). Only one isolate displayed a multiresistant pattern. Genotypic analysis of V. parahaemolyticus revealed a high degree of diversity among the isolates tested. The pulsed-field gel electrophoresis (PFGE) method distinguished 73 clonal groups, and the most numerous group consisted of 7 strains. Sequencing by the multilocus sequence typing (MLST) method showed 76 sequence types (STs), of which ST481 and ST1361 were most frequently identified. In addition, 51 (67.1%) new sequence types were discovered and added to the PubMLST international database.IMPORTANCE The presence of V. parahaemolyticus in seafood may pose a risk for consumers, especially in countries where shellfish are eaten raw. In recent years, a significant increase of food poisoning caused by these bacteria has been also observed in Europe. Our results highlight the high level of V. parahaemolyticus contamination of seafood, along with the isolates being potentially pathogenic for humans. However, the first-line antimicrobials, such as tetracyclines and fluoroquinolones, remained highly effective against V. parahaemolyticus The monitoring of antimicrobial resistance of isolates is important to ensure the high efficacy in the treatment of human infections. Most of V. parahaemolyticus strains possessed new sequence types (STs), which showed the high genetic diversity of the isolates tested.

Growth and Hemolysin Production Behavior of Vibrio parahaemolyticus in Different Food Matrices

The growth and hemolytic activity profiles of two Vibrio parahaemolyticus strains (ATCC 17802 and ATCC 33847) in shrimp, oyster, freshwater fish, pork, chicken, and egg fried rice were investigated, and a prediction system for accurate microbial risk assessment was developed. The two V. parahaemolyticus strains displayed a similar growth and hemolysin production pattern in the foods at 37°C. Growth kinetic parameters showed that V. parahaemolyticus displayed higher maximum specific growth rate and shorter lag time values in shrimp > freshwater fish > egg fried rice> oyster > chicken > pork. Notably, there was a similar number of V. parahaemolyticus in all of these samples at the stationary phase. The hemolytic activity of V. parahaemolyticus in foods increased linearly with time ( R² > 0.97). The rate constant ( K) of hemolytic activity was higher in shrimp, oyster, freshwater fish, and egg fried rice than in pork and chicken. Significantly higher hemolytic activity of V. parahaemolyticus was evident in egg fried rice > shrimp > freshwater fish > chicken > oyster > pork. The above-mentioned results indicate that V. parahaemolyticus could grow well regardless of the food type and that contrary to current belief, it displayed a higher hemolytic activity in some nonseafood products (freshwater fish, egg fried rice, and chicken) than in one seafood (oyster). The prediction system consisting of the growth model and hemolysin production algorithm reported here will fill a gap in predictive microbiology and improve significantly the accuracy of microbial risk assessment of V. parahaemolyticus.

Fingerprints of resistant Escherichia coli O157:H7 from vegetables and environmental samples

BACKGROUND

Some routes of transmission of Escherichia coli O157:H7 to fresh produce include contaminated irrigation water and manure polluted soils. The aim of the present study was to determine the genetic relationships of E. coli O157:H7 isolated from some produce growing region in Nigeria using enterobacterial repetitive intergenic consensus (ERIC) DNA fingerprinting analysis. A total of 440 samples comprising leafy greens, irrigation water, manure and soil were obtained from vegetable producing regions in Kano and Plateau States, Nigeria. Genes coding for the quinolone resistance-determinant (gyrA) and plasmid (pCT) coding for multidrug resistance (MDR) were determined using polymerase chain reaction (PCR) in 16 isolates that showed MDR.

RESULTS

Cluster analysis of the ERIC-PCR profiles based on band sizes revealed six main clusters from the sixteen isolates analysed. The largest cluster (cluster 3) grouped isolates from vegetables and manure at a similarity coefficient of 0.72.

CONCLUSION

The present study provides data that support the potential transmission of resistant strains of E. coli O157:H7 from vegetables and environmental sources to humans with potential public health implications, especially in developing countries. © 2017 Society of Chemical Industry.

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.

Spreading of Pandemic Vibrio parahaemolyticus O3:K6 and Its Serovariants: A Re-analysis of Strains Isolated from Multiple Studies

In China, V. parahaemolyticus has been a leading cause of foodborne outbreaks and bacterial infectious diarrhea since the 1990s, and most infections have been associated with the pandemic V. parahaemolyticus O3:K6 and its serovariants. However, a comprehensive overview of the sero-prevalence and genetic diversity of the pandemic V. parahaemolyticus clone in China is lacking. To compensate for this deficiency, pandemic isolates in both clinical and environmental Chinese samples collected from multiple studies were analyzed in this study. Surprisingly, as many as 27 clinical pandemic serovariants were identified and were widely distributed across nine coastal provinces and two inland provinces (Beijing and Sichuan). O3:K6, O4:K68, and O1:KUT represented the predominant clinical serovars. Only four environmental pandemic serovariants had previously been reported, and they were spread throughout Shanghai (O1:KUT, O3:K6), Jiangsu (O3:K6, O4:K48), Zhejiang (O3:K6), and Guangdong (O4:K9). Notably, 24 pandemic serovariants were detected within a short time frame (from 2006 to 2012). The pandemic isolates were divided into 15 sequence types (STs), 10 of which fell within clonal complex (CC) 3. Only three STs (ST3, ST192, and ST305) were identified in environmental isolates. Substantial serotypic diversity was mainly observed among isolates within pandemic ST3, which comprised 21 combinations of O/K antigens. The pandemic O3:K6 serotype showed a high level of sequence diversity, which was shared by eight different STs (ST3, ST227, ST431, ST435, ST487, ST489, ST526, and ST672). Antimicrobial susceptibility testing revealed that most isolates shared similar antibiotic susceptibility profiles. They were resistant to ampicillin but sensitive to most other drugs that were tested. In conclusion, the high levels of serotypic and genetic diversity of the pandemic clone suggest that the involved regions are becoming important reservoirs for the emergence of novel pandemic strains. We underscore the need for routine monitoring to prevent pandemic V. parahaemolyticus infection, which includes monitoring antimicrobial responses to avoid excessive misuse of antibiotics. Further investigations are also needed to delineate the specific mechanisms underlying the possible seroconversion of pandemic isolates.

Antibiotic and heavy-metal resistance of Vibrio parahaemolyticus isolated from fresh shrimps in Shanghai fish markets, China

Vibrio parahaemolyticus is a causative agent of human serious seafood-borne gastroenteritis disease and even death. Shrimps, often eaten raw or undercooked, are an important reservoir of the bacterium. In this study, we isolated and characterized a total of 400 V. parahaemolyticus strains from commonly consumed fresh shrimps (Litopenaeus vannamei, Macrobrachium rosenbergii, Penaeus monodon, and Exopalaemon carinicauda) in Shanghai fish markets, China in 2013-2014. The results revealed an extremely low occurrence of pathogenic V. parahaemolyticus carrying two major toxic genes (tdh and trh, 0.0 and 0.5 %). However, high incidences of antibiotic resistance were observed among the strains against ampicillin (99 %), streptomycin (45.25 %), rifampicin (38.25 %), and spectinomycin (25.50 %). Approximately 24 % of the strains derived from the P. monodon sample displayed multidrug resistant (MDR) phenotypes, followed by 19, 12, and 6 % from the E. carinicauda, L. vannamei, and M. rosenbergii samples, respectively. Moreover, tolerance to heavy metals of Cr(3+) and Zn(2+) was observed in 90 antibiotic resistant strains, the majority of which also displayed resistance to Cu(2+) (93.3 %), Pb(2+) (87.8 %), and Cd(2+)(73.3 %). The pulsed-field gel electrophoresis (PFGE)-based genotyping of these strains revealed a total of 71 distinct pulsotypes, demonstrating a large degree of genomic variation among the isolates. The wide distribution of MDR and heavy-metal resistance isolates in the PFGE clusters suggested the co-existence of a number of resistant determinants in V. parahaemolyticus population in the detected samples. This study provided data in support of aquatic animal health management and food safety risk assessment in aquaculture industry.

Feasibility of Using Multiple-Locus Variable-Number Tandem-Repeat Analysis for Epidemiology Study of Vibrio parahaemolyticus Infections

Vibrio parahaemolyticus causes foodborne gastroenteritis, which is often associated with the consumption of raw or undercooked shellfish. Molecular typing can provide critical information for detecting outbreaks and for source attribution. In this study, we describe the development and evaluation of an optimized multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) for the characterization of V. parahaemolyticus isolates. The discriminatory power of MLVA was compared to that of pulsed-field gel electrophoresis (PFGE) by typing 73 sporadic isolates. Epidemiologic concordance was evaluated by typing 23 isolates from five epidemiologically well-characterized outbreaks. The optimized MLVA was applied in early warning, epidemiological surveillance, and source tracking for V. parahaemolyticus infections. There was no significant difference in the discriminatory power of PFGE and MLVA with six or eight VNTR loci for the sporadic isolates. All isolates within an outbreak were indistinguishable by MLVA with six loci, except for one outbreak. Typically, the epidemiological survey could be initiated according to PFGE clusters. We applied MLVA with six loci on 22 isolates in two PFGE clusters. Isolates in one PFGE cluster were distinguished by MLVA. Although a follow-up investigation showed that both clusters had no epidemiological concordance, MLVA decreased the frequency of initiation of epidemiological surveys, thereby reducing labor costs. The ability of MLVA to trace the source of infection was evaluated by isolates from two outbreaks and shrimp samples. The isolates from one of outbreaks and a shrimp had the same MLVA type, suggesting that an epidemiological survey was initiated. Data from the epidemiological investigation subsequently indicated that contaminated shrimp from a nearby city (Dongguan) might be the source of the outbreak. In conclusion, these results indicate that the optimized MLVA may be a promising tool for early warning and epidemiological surveillance of V. parahaemolyticus infections.

Sero-Prevalence and Genetic Diversity of Pandemic V. parahaemolyticus Strains Occurring at a Global Scale

Pandemic Vibrio parahaemolyticus is an emerging public health concern as it has caused numerous gastroenteritis outbreaks worldwide. Currently, the absence of a global overview of the phenotypic and molecular characteristics of pandemic strains restricts our overall understanding of these strains, especially for environmental strains. To generate a global picture of the sero-prevalence and genetic diversity of pandemic V. parahaemolyticus, pandemic isolates from worldwide collections were selected and analyzed in this study. After a thorough analysis, we found that the pandemic isolates represented 49 serotypes, which are widely distributed in 22 countries across four continents (Asia, Europe, America and Africa). All of these serotypes were detected in clinical isolates but only nine in environmental isolates. O3:K6 was the most widely disseminated serotype, followed by O3:KUT, while the others were largely restricted to certain countries. The countries with the most abundant pandemic serotypes were China (26 serotypes), India (24 serotypes), Thailand (15 serotypes) and Vietnam (10 serotypes). Based on MLST analysis, 14 sequence types (STs) were identified among the pandemic strains, nine of which fell within clonal complex (CC) 3. ST3 and ST305 were the only two STs that have been reported in environmental pandemic strains. Pandemic ST3 has caused a wide range of infections in as many as 16 countries. Substantial serotypic diversity was mainly observed among isolates within pandemic ST3, including as many as 12 combinations of O/K serotypes. At the allele level, the dtdS and pntA, two loci that perfectly conserved in CC3, displayed a degree of polymorphism in some pandemic strains. In conclusion, we provide a comprehensive understanding of sero-prevalence and genetic differentiation of clinical and environmental pandemic isolates collected from around the world. Although, further studies are needed to delineate the specific mechanisms by which the pandemic strains evolve and spread, the findings in this study are helpful when seeking countermeasures to reduce the spread of V. parahaemolyticus in endemic areas.

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

Vibrio parahaemolyticus is the leading cause of foodborne outbreaks, particularly outbreaks associated with consumption of fish and shellfish, and represents a major threat to human health worldwide. This bacterium harbors two main virulence factors: the thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH). Additionally, various serotypes have been identified. The extensive use of antibiotics is a contributing factor to the increasing incidence of antimicrobial-resistant V. parahaemolyticus. In the current study, we aimed to determine the incidence and features of V. parahaemolyticus in ready-to-eat (RTE) foods in China. We found 39 V. parahaemolyticus strains on Chinese RTE foods through investigation of 511 RTE foods samples from 24 cities in China. All isolates were analyzed for the presence of tdh and trh gene by PCR, serotyping was performed using multiplex PCR, antibiotic susceptibility analysis was carried out using the disk diffusion method, and molecular typing was performed using enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) typing and multilocus sequence typing (MLST). The results showed that none of the isolates were positive for tdh and trh. Most of the isolates (33.3%) were serotype O2. Antimicrobial susceptibility results indicated that most strains were resistant to streptomycin (89.7%), cefazolin (51.3%), and ampicillin (51.3%). The isolates were grouped into five clusters by ERIC-PCR and four clusters by MLST. We updated 10 novel loci and 33 sequence types (STs) in the MLST database. Thus, our findings demonstrated the presence of V. parahaemolyticus in Chinese RTE foods, provided insights into the dissemination of antibiotic-resistant strains, and improved our knowledge of methods of microbiological risk assessment in RTE foods.

Prevalence, characterization, and antibiotic susceptibility of Vibrio parahaemolyticus isolated from retail aquatic products in North China

Background

Vibrio parahaemolyticus is a major foodborne pathogen, particularly in Asian countries. Increased occurrence of outbreaks of V. parahaemolyticus gastroenteritis in China indicates the need to evaluation of the prevalence of this pathogenic species. V. parahaemolyticus distribution in shellfish from the eastern coast of China has been reported previously. However, to date, the prevalence of V. parahaemolyticus in retail aquatic products in North China has not been determined. To investigate the prevalence of V. parahaemolyticus in aquatic products in North China, 260 aquatic product samples were obtained from retail markets in 6 provinces of North China from November to December in 2012 and July to August in 2013.

Results

V. parahaemolyticus was detected in 94 (36.2 %) of the samples by the most probable number method. The density of V. parahaemolyticus ranged from 1.50 to 1100 MPN/g. V. parahaemolyticus was detected at a rate of 50.0 % and 22.7 % in summer and in winter, respectively. The density of V. parahaemolyticus was significantly higher in summer than in winter, with mean levels of 16.5 MPN/g and 5.0 MPN/g, respectively. Among 145 V. parahaemolyticus isolates examined, none of the isolates possessed tdh and trh. In multiplex PCR-based O-antigen serotyping of these 145 isolates, all serotypes, other than O6, O7, and O9, were detected, and serotype O2 was found to be the most prevalent (detected in 54 isolates). The 145 isolates were grouped into 7 clusters by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) at a similarity coefficient of 0.66. The antimicrobial resistance patterns of these 145 isolates to 12 antimicrobial agents revealed that most of the isolates were resistant to streptomycin (86.2 %), while fewer were resistant to ampicillin (49.6 %), cefazolin (43.5 %), cephalothin (35.9 %), and kanamycin (22.1 %). All of the examined isolates were susceptible to azithromycin and chloramphenicol.

Conclusions

The findings of this study will help in defining appropriate monitoring programs, understanding of the dissemination of antibiotic resistant strains, and providing information for the assessment of exposure to this microorganism at the consumption level.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0650-6) contains supplementary material, which is available to authorized users.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

First detection of AmpC β-lactamase bla(CMY-2) on a conjugative IncA/C plasmid in a Vibrio parahaemolyticus isolate of food origin

Vibrio parahaemolyticus is an important causative agent of gastroenteritis, with the consumption of contaminated seafood being the major transmission route. Resistance to penicillin is common among V. parahaemolyticus strains, whereas cephalosporin resistance remains rare. In an attempt to assess the current prevalence and characteristics of antibiotic resistance of this pathogen in common food samples, a total of 54 (17% of the total samples) V. parahaemolyticus strains were isolated from 318 meat and seafood samples purchased from supermarkets and wet markets in Shenzhen, China, in 2013. These isolates exhibited high-level resistance to ampicillin, yet they were mostly susceptible to other antimicrobials, except for two that were resistant to extended-spectrum cephalosporins. The β-lactamase gene blaPER-1 was detectable in one strain, V. parahaemolyticus V43, which was resistant to both third- and fourth-generation cephalosporins. Compared to other blaPER-1-positive V. parahaemolyticus strains reported in our previous studies, strain V43 was found to harbor an ∼200-kb conjugative plasmid carrying genes that were different from the antimicrobial resistance genes reported from the previous studies. The β-lactamase gene blaCMY-2 was detectable for the first time in another V. parahaemolyticus isolate, V4, which was resistant to third-generation cephalosporins. This blaCMY-2 gene was shown to be located in an ∼150-kb IncA/C-type conjugative plasmid with a genetic structure consisting of traB-traV-traA-ISEcp1-blaCMY-2-blc-sugE-encR-orf1-orf2-orf3-orf4-dsbC-traC, which is identical to that of other IncA/C conjugative plasmids in Enterobacteriaceae, albeit with a different size. These findings indicate that the transmission of extended-spectrum-β-lactamase (ESBL) and AmpC β-lactamase genes via conjugative plasmids can mediate the development of extended-spectrum cephalosporin resistance in V. parahaemolyticus, thereby posing a potential threat to public health.

Prevalence and genetic diversity of clinical Vibrio parahaemolyticus isolates from China, revealed by multilocus sequence typing scheme

The population structure of clinical Vibrio parahaemolyticus isolates spreading in China remains undefined. We brought 218 clinical isolates from the pubMLST database originating from different regions of China collected since the year of 1990, analyzed by multilocus sequence typing (MLST), to elucidate the prevalence and genetic diversity of V. parahaemolyticus circulating in Chinese population. The MLST scheme produced 137 sequence types (STs). These STs were clustered into six clonal complexes (CCs), six doublets, and 91 singletons, exhibiting a high level of genetic diversity. However, less diversity was displayed on the peptide level: only 46 different peptide sequence type (pST) were generated, with pST2 (44.0%, 96/218) and pST1 (15.1%, 33/218) the predominant. Further analysis confirmed all the pSTs belong to a single complex founded by pST1, pST2, pST3, and pST4. recA presented the highest degree of nucleotide diversity (0.026) and the largest number of variable sites (176) on the nucleotide level. pyrC was the most diverse locus on the peptide level, possessing the highest percentage of variable sites (9.2%, 15/163). Significant linkage disequilibrium with the alleles was detected when the Standardized Index of Association (I^S_A) was calculated both for the entire isolates collection (0.7169, P < 0.01) and for the 137 STs (I^S_A = 0.2648, P < 0.01). In conclusion, we provide an overview of prevalence and genetic diversity of clinical V. parahaemolyticus spreading in Chinese population using MLST analysis. The results would offer genetic evidences for uncovering the microevolution relationship of V. parahaemolyticus populations.

Population structure of clinical Vibrio parahaemolyticus from 17 coastal countries, determined through multilocus sequence analysis

Vibrio parahaemolyticus is a leading cause of food-borne gastroenteritis worldwide. Although this bacterium has been the subject of much research, the population structure of clinical strains from worldwide collections remains largely undescribed, and the recorded outbreaks of V. parahaemolyticus gastroenteritis highlight the need for the subtyping of this species. We present a broad phylogenetic analysis of 490 clinical V. parahaemolyticus isolates from 17 coastal countries through multilocus sequence analysis (MLST). The 490 tested isolates fell into 161 sequence types (STs). The eBURST algorithm revealed that the 161 clinically relevant STs belonged to 8 clonal complexes, 11 doublets, and 94 singletons, showing a high level of genetic diversity. CC3 was found to be a global epidemic clone of V. parahaemolyticus, and ST-3 was the only ST with an international distribution. recA was observed to be evolving more rapidly, exhibiting the highest degree of nucleotide diversity (0.028) and the largest number of polymorphic nucleotide sites (177). We also found that the high variability of recA was an important cause of differences between the results of the eBURST and ME tree analyses, suggesting that recA has a much greater influence on the apparent evolutionary classification of V. parahaemolyticus based on the current MLST scheme. In conclusion, it is evident that a high degree of genetic diversity within the V. parahaemolyticus population and multiple sequence types are contributing to the burden of disease around the world. MLST, with a fully extractable database, is a powerful system for analysis of the clonal relationships of strains at a global scale. With the addition of more strains, the pubMLST database will provide more detailed and accurate information, which will be conducive to our future research on the population structure of V. parahaemolyticus.

Suitability of the molecular subtyping methods intergenic spacer region, direct genome restriction analysis, and pulsed-field gel electrophoresis for clinical and environmental Vibrio parahaemolyticus isolates

Vibrio parahaemolyticus is the leading cause of infectious illness associated with seafood consumption in the United States. Molecular fingerprinting of strains has become a valuable research tool for understanding this pathogen. However, there are many subtyping methods available and little information on how they compare to one another. For this study, a collection of 67 oyster and 77 clinical V. parahaemolyticus isolates were analyzed by three subtyping methods--intergenic spacer region (ISR-1), direct genome restriction analysis (DGREA), and pulsed-field gel electrophoresis (PFGE)--to determine the utility of these methods for discriminatory subtyping. ISR-1 analysis, run as previously described, provided the lowest discrimination of all the methods (discriminatory index [DI]=0.8665). However, using a broader analytical range than previously reported, ISR-1 clustered isolates based on origin (oyster versus clinical) and had a DI=0.9986. DGREA provided a DI=0.9993-0.9995, but did not consistently cluster the isolates by any identifiable characteristics (origin, serotype, or virulence genotype) and ∼ 15% of isolates were untypeable by this method. PFGE provided a DI=0.9998 when using the combined pattern analysis of both restriction enzymes, SfiI and NotI. This analysis was more discriminatory than using either enzyme pattern alone and primarily grouped isolates by serotype, regardless of strain origin (clinical or oyster) or presence of currently accepted virulence markers. These results indicate that PFGE and ISR-1 are more reliable methods for subtyping V. parahemolyticus, rather than DGREA. Additionally, ISR-1 may provide an indication of pathogenic potential; however, more detailed studies are needed. These data highlight the diversity within V. parahaemolyticus and the need for appropriate selection of subtyping methods depending on the study objectives.