Pulsed-field gel electrophoresis and PCR characterization of environmental Vibrio parahaemolyticus strains of different origins

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.

Characterization of multidrug resistance in Vibrio species isolated from marine invertebrates from Andaman Sea

This study describes the abundance of multidrug-resistant Vibrios associated with marine invertebrate hosts from the Andaman Sea, India. Thirty-eight Vibrio strains were isolated from surface mucus layers of coral Porites, Goniastrea, Pocillopora, Fungia, and eggs of spiny lobster (Panulirus penicillatus). Phenotypically, the majority of strains exhibited growth at a wide range of temperatures, salt tolerance, and diverse nutritional requirements. All the strains had more than 97% 16S rRNA sequence similarity with type species of the genus Vibrio where Vibrio fortis, and Vibrio alginolyticus were predominant. Multilocus Sequence Analysis (MLSA) using eight housekeeping genes namely ftsZ, gapA, gyrB, mreB, pyrH, recA, rpoA, and topA distributed the strains into 6 reported clades i.e., Harveyi, Ponticus, Nereis, Orientalis, Splendidus, and Mediterranei where nearly half of the total strains represented the clade Harveyi, followed by the clade Splendidus. Likewise, the PFGE profile indicated genomic heterogeneity among the strains resulting in their distribution in five major clusters. Resistance to different antimicrobials was tested following the disc diffusion method where all strains were found susceptible to chloramphenicol (30 µg) and resistant to streptomycin (10 µg), vancomycin (30 µg), sulfamethoxazole-trimethoprim (25 µg). Moreover, the resistant phenotype to other antimicrobials confirmed the abundance of multidrug resistance strains in this marine environment.

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.

Development of an Electrochemical DNA Biosensor to Detect a Foodborne Pathogen

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, significantly affecting the rate of human mortality and morbidity. Conventional methods for the detection of V. parahaemolyticus such as culture-based methods, immunological assays, and molecular-based methods require complicated sample handling and are time-consuming, tedious, and costly. Recently, biosensors have proven to be a promising and comprehensive detection method with the advantages of fast detection, cost-effectiveness, and practicality. This research focuses on developing a rapid method of detecting V. parahaemolyticus with high selectivity and sensitivity using the principles of DNA hybridization. In the work, characterization of synthesized polylactic acid-stabilized gold nanoparticles (PLA-AuNPs) was achieved using X-ray Diffraction (XRD), Ultraviolet-visible Spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM), Field-emission Scanning Electron Microscopy (FESEM), and Cyclic Voltammetry (CV). We also carried out further testing of stability, sensitivity, and reproducibility of the PLA-AuNPs. We found that the PLA-AuNPs formed a sound structure of stabilized nanoparticles in aqueous solution. We also observed that the sensitivity improved as a result of the smaller charge transfer resistance (Rct) value and an increase of active surface area (0.41 cm²). The development of our DNA biosensor was based on modification of a screen-printed carbon electrode (SPCE) with PLA-AuNPs and using methylene blue (MB) as the redox indicator. We assessed the immobilization and hybridization events by differential pulse voltammetry (DPV). We found that complementary, non-complementary, and mismatched oligonucleotides were specifically distinguished by the fabricated biosensor. It also showed reliably sensitive detection in cross-reactivity studies against various food-borne pathogens and in the identification of V. parahaemolyticus in fresh cockles.

Characterization of Pathogenic Vibrio parahaemolyticus from the Chesapeake Bay, Maryland

Vibrio parahaemolyticus is the leading cause of bacterial gastroenteritis associated with seafood consumption in the United States. Here we investigated the presence of virulence factors and genetic diversity of V. parahaemolyticus isolated from water, oyster, and sediment samples from the Chesapeake Bay, Maryland. Of more than 2,350 presumptive Vibrio collected, more than half were confirmed through PCR as V. parahaemolyticus, with 10 encoding both tdh and trh and 6 encoding only trh. Potentially pathogenic V. parahaemolyticus were then serotyped with O1:KUT and O3:KUT predominant. Furthermore, pulsed-field gel electrophoresis was performed and the constructed dendrogram displayed high diversity, as did results from multiple-locus VNTR analysis. Vibrio parahaemolyticus was readily isolated from Chesapeake Bay waters but was less frequently isolated from oyster and sediment samples collected during this study. Potentially pathogenic V. parahaemolyticus was isolated in fewer numbers and the isolates displayed expansive diversity. Although characteristics of the pathogenic V. parahaemolyticus were highly variable and the percent of pathogenic V. parahaemolyticus detected was low, it is important to note that, pathogenic V. parahaemolyticus are present in the Chesapeake Bay, warranting seafood monitoring to minimize risk of disease for the public, and to reduce the economic burden of V. parahaemolyticus related illness.

Genetic characterization of Vibrio vulnificus strains isolated from oyster samples in Mexico

Vibrio vulnificus strains were isolated from oysters that were collected at the main seafood market in Mexico City. Strains were characterized with regard to vvhA, vcg genotype, PFGE, multilocus sequence typing (MLST), and rtxA1. Analyses included a comparison with rtxA1 reference sequences. Environmental (vcgE) and clinical (vcgC) genotypes were isolated at nearly equal percentages. PFGE had high heterogeneity, but the strains clustered by vcgE or vcgC genotype. Select housekeeping genes for MLST and primers that were designed for rtxA1 domains divided the strains into two clusters according to the E or C genotype. Reference rtxA1 sequences and those from this study were also clustered according to genotype. These results confirm that this genetic dimorphism is not limited to vcg genotyping, as other studies have reported. Some environmental C genotype strains had high similarity to reference strains, which have been reported to be virulent, indicating a potential risk for oyster consumers in Mexico City.

Development of a colony hybridization method for the enumeration of total and potentially enteropathogenic Vibrio parahaemolyticus in shellfish

Vibrio parahaemolyticus is a marine microorganism, recognized as cause of gastroenteritis outbreaks associated with seafood consumption. In this study the development and the in-house validation of a colony hybridization method for the enumeration of total and potentially pathogenic V. parahaemolyticus is reported. The method included a set of three controls (process, hybridization and detection control) for the full monitoring of the analytical procedure. Four digoxigenin-labeled probes were designed for pathogenic strains enumeration (tdh1, tdh2, trh1 and trh2 probes) and one for total V. parahaemolyticus count (toxR probe). Probes were tested on a panel of 70 reference strains and 356 environmental, food and clinical isolates, determining the inclusivity (tdh: 96.7%, trh: 97.8%, toxR: 99.4%) and the exclusivity (100% for all probes). Accuracy and linearity of the enumeration were evaluated on pure and mixed cultures: slopes of the regression lines ranged from 0.957 to 1.058 depending on the target gene and R(2) was greater than or equal to 0.989 for all reactions. Evaluation was also carried on using four experimentally contaminated seafood matrices (shellfish, finfish, crustaceans and cephalopods) and the slopes of the curves varied from 0.895 (finfish) to 0.987 (cephalopods) for the counts of potentially pathogenic V. parahaemolyticus (R(2)≥0.965) and from 0.965 to 1.073 for total V. parahaemolyticus enumeration (R(2)≥0.981). Validation was performed on 104 naturally contaminated shellfish samples, analyzed in parallel by colony hybridization, ISO/TS 21872-1 and MPN enumeration. Colony hybridization and ISO method showed a relative accuracy of 86.7%, and a statistically significant correlation was present between colony hybridization enumeration and MPN results (r=0.744, p<0.001). The proposed colony hybridization can be a suitable alternative method for the enumeration of total and potentially pathogenic V. parahaemolyticus in seafood.

Rapid identification of Vibrio parahaemolyticus isolated from shellfish, sea water and sediments of the Khnifiss lagoon, Morocco, by MALDI-TOF mass spectrometry

We establish the presence of Vibrio parahaemolyticus and deepen the comparison of isolates using MALDI-TOF MS for the typing of isolates originating from the Khnifiss lagoon (Morocco). Amongst 48 samples from sea water, sediment and shellfish isolated from different sites of Khnifiss lagoon, Morocco, we obtained 22 isolates of V. parahaemolyticus identified by Vitek 2™ System (bioMérieux) and MALDI Biotyper™ (Bruker Daltonics). All isolates were highly resistant to ampicillin and ticarcillin, moderately resistant to cefalotin, but sensitive to 16 other antimicrobials tested. MALDI-TOF MS was used to discriminate between closely related environmental strains of V. parahaemolyticus. A clustering and distribution based on MALDI-TOF spectra were generated using the BioTyper 1.1™ software. Despite low diversity in regard to the biochemical characteristics and antimicrobial resistance, the isolates evoke a larger biodiversity when analysed through mass spectra of abundant proteins. Different evaluations of a cut-off value showed that, when placed at a 10% threshold of the whole diversity, isolates differed by at least three mass peaks.