Virulence of thermolable haemolysi tlh, gastroenteritis related pathogenicity tdh and trh of the pathogens Vibrio Parahemolyticus in Viable but Non-Culturable (VBNC) state

Characterization of the genome and cell invasive phenotype of Vibrio diabolicus Cg5 isolated from mass mortality of Pacific oyster, Crassostrea gigas

Vibrio is an important group of aquatic animal pathogens, which has been identified as the main pathogenic factor causing mass summer mortality of Crassostrea gigas in northern China. This study aims to investigate the potential pathogenic mechanisms of Vibrio Cg5 isolate in C. gigas. We sequenced and annotated the genome of Vibrio Cg5 to analyze potential virulence factors. The gentamicin protection assays were performed with C. gigas primary cells to reveal the cell-invasive behavior of Cg5. The genome analysis showed that Cg5 was a strain of human disease-associated pathogen with multiple antibiotic resistance, and four virulence factors associated with intracellular survival were present in the genome. The gentamicin protection assays showed that Cg5 could potentially invade the cells of C. gigas, indicating that Cg5 could be a facultative intracellular pathogen of C. gigas. These results provide insights into the pathogenic mechanism of V. diabolicus, an emerging pathogenic Vibrio on aquatic animals, which would be valuable in preventing and controlling diseases in oysters.

Metal-Organic Frameworks-Based Sensors for Food Safety

Food contains a variety of poisonous and harmful substances that have an impact on human health. Therefore, food safety is a worldwide public concern. Food detection approaches must ensure the safety of food at every step of the food supply chain by monitoring and evaluating all hazards from every single step of food production. Therefore, early detection and determination of trace-level contaminants in food are one of the most crucial measures for ensuring food safety and safeguarding consumers’ health. In recent years, various methods have been introduced for food safety analysis, including classical methods and biomolecules-based sensing methods. However, most of these methods are laboratory-dependent, time-consuming, costly, and require well-trained technicians. To overcome such problems, developing rapid, simple, accurate, low-cost, and portable food sensing techniques is essential. Metal-organic frameworks (MOFs), a type of porous materials that present high porosity, abundant functional groups, and tunable physical and chemical properties, demonstrates promise in large-number applications. In this regard, MOF-based sensing techniques provide a novel approach in rapid and efficient sensing of pathogenic bacteria, heavy metals, food illegal additives, toxins, persistent organic pollutants (POPs), veterinary drugs, and pesticide residues. This review focused on the rapid screening of MOF-based sensors for food safety analysis. Challenges and future perspectives of MOF-based sensors were discussed. MOF-based sensing techniques would be useful tools for food safety evaluation owing to their portability, affordability, reliability, sensibility, and stability. The present review focused on research published up to 7 years ago. We believe that this work will help readers understand the effects of food hazard exposure, the effects on humans, and the use of MOFs in the detection and sensing of food hazards.

Quantitative and specific detection of viable pathogens on a portable microfluidic chip system by combining improved propidium monoazide (PMAxx) and loop-mediated isothermal amplification (LAMP)

An accurate and specific detection of viable Candida albicans (C. albicans) in vaginal discharge is crucial for the diagnosis of vulvovaginal candidiasis (VVC) and assessment of antifungal effects. In this study, improved propidium monoazide (PMAxx) and loop-mediated isothermal amplification (LAMP) were used for the first time to distinguish between viable and dead C. albicans. A portable microfluidic chip system was developed to detect multiple viable pathogens in parallel. The consumption of samples and reagents in per reaction cell were only 0.94 μL, less than 1/25 of the conventional 25 μL Eppendorf tubular test method, both significantly reducing testing cost and greatly simplifying the detection of multiple viable pathogens. The concentration of PMAxx was optimized against C. albicans at 4.0 log CFU mL^-1 to 5.0 log CFU mL^-1, and 1 μM PMAxx was proven to be suitable for the detection of C. albicans in clinical samples. When testing mixtures containing different ratios of viable to dead C. albicans, PMAxx-LAMP could circumvent the signal arising from dead cells and, therefore, reflected the abundance of viable cells precisely. Furthermore, the suitability of this technique to evaluate the effects of antifungal agents, including clotrimazole, miconazole, and tioconazole, was assessed. Finally, the viability of Escherichia coli (E. coli) and C. albicans were detected on the portable microfluidic chip system. PMAxx-LAMP based portable microfluidic chip system was determined to be a feasible technique for assessing the viability of multiple pathogens in gynecology and might provide insights into new VVC treatment strategies.

Detection of viable but nonculturable Vibrio parahaemolyticus induced by prolonged cold-starvation using propidium monoazide real-time polymerase chain reaction

Viable but nonculturable (VBNC) Vibrio parahaemolyticus cannot be detected by the standard cultivation-based methods. In this study, commonly used viability assessment methods were evaluated for the detection of V. parahaemolyticus in a VBNC state. Vibrio parahaemolyticus cells exposed to nutrient deficiency at cold temperature were used for epifluorescence microscopy with SYTO₉ and propidium iodide (PI) staining and real-time polymerase chain reaction (qPCR) with propidium monoazide (PMA), and its resuscitative ability was determined by a temperature upshift in freshly prepared artificial sea water (ASW; pH 7) fluids. Viable cells with intact membranes always exceeded 5·0 log CFU per ml in ASW microcosms at 4°C. After 80 days, cycle thresholds for V. parahaemolyticus ATCC 27969 were 16·15-16·69. During cold-starvation, PMA qPCR selectively excluded DNAs from heat-killed cells. However, there may be some penetration of PMA into undamaged cells that persisted in ASW for 150 days, as evidenced by their ability to resuscitate from a VBNC state after a temperature upshift (25°C); V. parahaemolyticus ATCC 33844 and V. parahaemolyticus ATCC 27969 were successfully reactivated from a VBNC state in ASW microcosms containing <5% NaCl, following enrichment in ASW medium (pH 7). SIGNIFICANCE AND IMPACT OF THE STUDY: Few studies have evaluated the characteristics of and detection methods for viable but nonculturable (VBNC) Vibrio parahaemolyticus induced by cold-starvation. Currently, VBNC cells are routinely detected by SYTO₉ and propidium iodide double staining. However, viable cell counts might be overestimated by this approach, suggesting that the fluorescence dyes may be ineffective for accurately determining the viability of bacterial cells. We demonstrated that quantitative real-time polymerase chain reaction with propidium monoazide, which selectively permeates damaged cell membranes, can be used to obtain viable cell counts of V. parahaemolyticus after its evolution to a VBNC state under cold-starvation conditions.

Molecular mechanisms of Vibrio parahaemolyticus pathogenesis

Vibrio parahaemolyticus is a Gram-negative halophilic bacterium that is mainly distributed in the seafood such as fish, shrimps and shellfish throughout the world. V. parahaemolyticus can cause diseases in marine aquaculture, leading to huge economic losses to the aquaculture industry. More importantly, it is also the leading cause of seafood-borne diarrheal disease in humans worldwide. With the development of animal model, next-generation sequencing as well as biochemical and cell biological technologies, deeper understanding of the virulence factors and pathogenic mechanisms of V. parahaemolyticus has been gained. As a globally transmitted pathogen, the pathogenicity of V. parahaemolyticus is closely related to a variety of virulence factors. This article comprehensively reviewed the molecular mechanisms of eight types of virulence factors: hemolysin, type III secretion system, type VI secretion system, adhesion factor, iron uptake system, lipopolysaccharide, protease and outer membrane proteins. This review comprehensively summarized our current understanding of the virulence factors in V. parahaemolyticus, which are potentially new targets for the development of therapeutic and preventive strategies.