Simultaneous isolation and enumeration of virulent Vibrio cholerae and Vibrio vulnificus using an advanced MPN-PCR method

Nanotechnology-based analytical techniques for the detection of contaminants in aquatic products

Food safety of aquatic products has attracted considerable attention worldwide. Although a series of conventional bioassays and instrumental methods have been developed for the detection of pathogenic bacteria, heavy metal residues, marine toxins, and biogenic amines during the production and storage of fish, shrimp, crabs et al., the nanotechnology-based analyses still have their advantages and are promising since they are cost-efficient, highly sensitive and selective, easy to conduct, facial design, often require no sophisticated instruments but with excellent detection performance. This review aims to summarize the advances of various biosensing strategies for bacteria, metal ions, and small molecule contaminants in aquatic products during the last five years, The review highlights the development in nanotechnologies applied for biorecognition process, signal transduction and amplification methods in each novel approach, the nuclease-mediated DNA amplification, nanomaterials (noble metal nanoparticle, metal-organic frameworks, carbon dots), lateral flow-based biosensor, surface-enhanced Raman scattering, microfluidic chip, and molecular imprinting technologies were especially emphasized. Moreover, this study provides a view of current accomplishments, challenges, and future development directions of nanotechnology in aquatic product safety evaluation.

Construction of mPt/ICG-αA nanoparticles with enhanced phototherapeutic activities for multidrug-resistant bacterial eradication and wound healing

The emergence of multidrug-resistant (MDR) bacterial infections calls for novel strategies for effective bacterial inhibition and wound healing. Phototherapeutic approaches are promising in treating bacterial infection because of their high efficiency, noninvasiveness, and few side effects; however, their antibacterial effect is limited by the formation of biofilms in wounds. Herein, we report novel composite nanoparticles (mPt/ICG-αA NPs) combining mesoporous platinum (mPt) nanoparticles, indocyanine green (ICG) and α-amylase (αA) for combating MDR bacteria and treating wound infection, which integrates a triple bacterial inhibition mechanism arising from the combination of photodynamic therapy (PDT), photothermal therapy (PTT) and α-amylase enzymatic activities. The combination of mPt and ICG significantly enhances the effect of PTT and the temperature can be increased up to 80.8 °C to induce efficacious bacterial degeneration. Meanwhile, mPt/ICG-αA (mPIA) NPs with a low concentration of 25 μg mL-1 exhibited a remarkable catalase activity (CAT) and could continuously decompose endogenous H2O2 into O2 in a hypoxic microenvironment, thereby enhancing the PDT effect to achieve broad-spectrum bactericidal activity. mPIA NPs showed excellent MDR antibacterial efficiency against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli), and the bactericidal rate reached up to 99.0% and 97.2% with single 808 nm near-infrared light irradiation, respectively. mPIA NPs also exhibited an excellent ability to destroy biofilms and biocompatibility. Animal experiments further suggested that mPIA NPs could achieve the successful repairment of wounds infected with S. aureus in living systems, while this platform demonstrated negligible toxicity towards mice. Considering the superior performances of mPIA NPs, the synergistic αA-CAT-PDT-PTT boosted therapeutic activity presented in the current work provides a promising method to effectively fight against biofilm-related infectious diseases and wound healing.

An Assay Combining Droplet Digital PCR With Propidium Monoazide Treatment for the Accurate Detection of Live Cells of Vibrio vulnificus in Plasma Samples

Vibrio vulnificus (V. vulnificus) is one of the most common pathogenic Vibrio species to humans; therefore, the establishment of timely and credible detection methods has become an urgent requirement for V. vulnificus illness surveillance. In this study, an assay combining droplet digital PCR (ddPCR) with propidium monoazide (PMA) treatment was developed for detecting V. vulnificus. The primers/probes targeting the V. vulnificus hemolysin A (vvhA) gene, amplification procedures, and PMA processing conditions involved in the assay were optimized. Then, we analyzed the specificity, sensitivity, and ability to detect live cell DNA while testing the performance of PMA-ddPCR in clinical samples. The optimal concentrations of primers and probes were 1.0 and 0.3 μM, respectively. The annealing temperature achieving the highest accuracy in ddPCR assay was 60°C. With an initial V. vulnificus cell concentration of 10⁸ CFU/mL (colony-forming units per milliliter), the optimal strategy to distinguish live cells from dead cells was to treat samples with 100 μM PMA for 15 min in the dark and expose them to LED light with an output wavelength of 465 nm for 10 min. The specificity of the PMA-ddPCR assay was tested on 27 strains, including seven V. vulnificus strains and 20 other bacterial strains. Only the seven V. vulnificus strains were observed with positive signals in specificity analysis. Comparative experiments on the detection ability of PMA-ddPCR and PMA-qPCR in pure cultures and plasma samples were performed. The limit of detection (LOD) and the limit of quantitation (LOQ) in pure culture solutions of V. vulnificus were 29.33 and 53.64 CFU/mL in PMA-ddPCR, respectively. For artificially clinical sample tests in PMA-ddPCR, V. vulnificus could be detected at concentrations as low as 65.20 CFU/mL. The sensitivity of the PMA-ddPCR assay was 15- to 40-fold more sensitive than the PMA-qPCR in this study. The PMA-ddPCR assay we developed provides a new insight to accurately detect live cells of V. vulnificus in clinical samples, which is of great significance to enhance public health safety and security capability and improve the emergency response level for V. vulnificus infection.