Research on the contamination, drug resistance and molecular typing of Vibrio parahaemolyticus isolated from aquatic products in Nanchang City market / 中国热带医学

@#Abstract: Objective　To understand the contamination status, drug resistance, virulence gene carrying status, and molecular typing characteristics of Vibrio parahaemolyticus (VP) in aquatic products sold in Nanchang City. Methods　A total of 170 commercial crayfishes, freshwater fish frogs and related smears samples were collected from various farmers' markets in Nanchang from March to September 2021. The strains of V. parahaemolyticus were detected and isolated from the samples. Antibiotic resistance test, virulence gene test, and pulsed-field gel electrophoresis (PFGE) molecular typing analysis were carried out. Results　Among the collected samples, V.parahaemolyticus was only isolated from crayfish and crayfish smear samples, with a total of 35 strains of VP isolated. No V.parahaemolyticus strain was isolated from other freshwater fish, frogs, and their smear samples. Among the 17 common antibiotics tested, only two trains showed resistance to ampicillin, and one strain to streptomycin, , and all were sensitive to other antibiotics; all 35 strains of V. parahaemolyticus carried the gene, but only one strain carried the heat-resistant related hemolysin gene trh, and no direct heat-resistant hemolysin gene tdh positive strain was found; PFGE pattern clustering showed that there was no strain with the same PFGE pattern, and there was no obvious dominant cluster among these strains, and their genetic relationship was relatively distant. Conclusions　The contamination of V. parahaemolyticus in small and medium-sized crayfish sold in the market in Nanchang City is relatively serious. The V. parahaemolyticus isolates in these polluted crayfish generally do not carry key virulence genes such as tdh, are sensitive to common antibiotics, and only have low-level resistance to ampicillin and streptomycin. PFGE pattern clustering showed that V. parahaemolyticus does not have no obvious dominant cluster, and these strains have rich genetic diversity, indicating that they may have different sources.

CqsA-introduced quorum sensing inhibits type VI secretion system 2 through an OpaR-dependent pathway in Vibrio parahaemolyticus.

The well-known food-borne pathogen Vibrio parahaemolyticus employs at least three quorum sensing signals to maintain its high environmental adaptability. V. parahaemolyticus CqsA, the synthase involved in 3-hydroxyundecan-4-one quorum sensing signal, introduces a quorum sensing network. The V. parahaemolyticus virulent factor type VI secretion system 2 (T6SS2), which is associated with adhesion to host cells, was previously reported to be regulated by a quorum sensing system. Herein, we set out to determine the role of CqsA-introduced quorum sensing (CIQS) in T6SS2-associated virulent regulation. Using a tandem mass tag (TMT)-based quantitative proteomics assay, 17 T6SS2 proteins were found having significantly higher abundances in the ΔcqsA strain than in the wild type strain. TMT proteomics assay results were confirmed by a parallel reaction-monitoring (PRM)-based proteomics assay. Two T6SS2 up-regulators, OpaR and CalR, were found under control of CIQS in the TMT proteomics assay, while OpaR was down-regulated and CalR was up-regulated by CIQS. Thus, it was hypothesized that CIQS would inhibit T6SS2 with an OpaR-dependent mechanism. Epistasis experiment with quantitative PCR was designed to analyze the role of OpaR in the process of CIQS inhibiting T6SS2 production. The mRNA levels of T6SS2 genes were up-regulated in the ΔcqsA strain while down-regulated in the ΔopaR strain and in the ΔcqsAΔopaR mutant, indicating that OpaR plays a predominant role in the regulation of T6SS2 by CIQS. Using a cell adhesion assay, we further found that the T6SS2-dependent adhesion activity of V. parahaemolyticus to Hela cells was also inhibited by CIQS and the inhibition was OpaR-dependent. In this study, we confirmed that V. parahaemolyticus CIQS inhibited T6SS2 through an OpaR-dependent pathway. It enriches the knowledge of how V. parahaemolyticus quorum sensing regulates its virulence.

Comparative evaluation of the efficiency of the BG-Sentinel trap, CDC light trap and Mosquito-oviposition trap for the surveillance of vector mosquitoes.

BACKGROUND: The surveillance of vector mosquitoes is important for the control of mosquito-borne diseases. To identify a suitable surveillance tool for the adult dengue vector Aedes albopictus, the efficacy of the BG-Sentinel trap, CDC light trap and Mosquito-oviposition trap (MOT) on the capture of vector mosquitoes were comparatively evaluated in this study. METHODS: The capture efficiencies of the BG-Sentinel trap, CDC light trap and Mosquito-oviposition trap for common vector mosquitoes were tested in a laboratory setting, through the release-recapture method, and at two field sites of Guangzhou, China from June 2013 to May 2014. The captured mosquitoes were counted, species identified and compared among the three traps on the basis of species. RESULTS: In the release-recapture experiments in a laboratory setting, the BG-Sentinel trap caught significantly more Aedes albopictus and Culex quinquefasciatus than the CDC light trap and Mosquito-ovitrap, except for Anopheles sinensis. The BG-Sentinel trap had a higher efficacy in capturing female rather than male Ae. albopictus and Cx. quinquefasciatus, but the capture in CDC light traps displayed no significant differences. In the field trial, BG-Sentinel traps collected more Aedes albopictus than CDC light traps and MOTs collected in both urban and suburban areas. The BG-Sentinel trap was more sensitive for monitoring the population density of Aedes albopictus than the CDC light trap and MOT during the peak months of the year 2013. However, on an average, CDC light traps captured significantly more Cx. quinquefasciatus than BG-Sentinel traps. The population dynamics of Cx. quinquefasciatus displayed a significant seasonal variation, with the lowest numbers in the middle of the year. CONCLUSIONS: This study indicates that the BG-Sentinel trap is more effective than the commonly used CDC light trap and MOT in sampling adult Aedes albopictus and Culex quinquefasciatus. We recommend its use in the surveillance of dengue vector mosquitoes in China.