Natural occurrences and characterization of Elizabethkingia miricola infection in cultured bullfrogs (Rana catesbeiana).

Introduction: The bacterium Elizabethkingia miricola is a multispecies pathogen associated with meningitis-like disease that has been isolated from several amphibian species, including the bullfrog, but this is the first isolation in Guangxi. In the present study, the dominant bacteria were isolated from the brains of five bullfrogs with meningitis-like disease on a South China farm in Guangxi. Methods: The NFEM01 isolate was identified by Gram staining; morphological observations; 16S rRNA, rpoB, and mutT-based phylogenetic tree analysis; and physiochemical characterization and was subjected to drug sensitivity and artificial infection testing. Results and discussion: As a result of identification, the NFEM01 strain was found to be E. miricola. An artificial infection experiment revealed that NFEM01 infected bullfrogs and could cause symptoms of typical meningitis-like disease. As a result of the bacterial drug sensitivity test, NFEM01 is highly sensitive to mequindox, rifampicin, enrofloxacin, nitrofural, and oxytetracycline and there was strong resistance to gentamicin, florfenicol, neomycin, penicillin, amoxicillin, doxycycline, and sulfamonomethoxine. This study provides a reference to further study the pathogenesis mechanism of E. miricola-induced bullfrog meningitislike disease and its prevention and treatment.

Study on aptamer based high throughput approach identifies natural ingredients against RGNNV.

Nervous necrosis virus (NNV) is one of the most destructive pathogens in marine fish aquaculture and is capable of infecting more than 50 fish species worldwide, which resulted in great economic losses. Effective drugs for managing NNV infection are urgently required. Medicinal plants have been known for thousands of years and benefit of medicinal plants against pathogens in aquaculture have emerged. Nowadays, the most commonly used method for detecting virus infection and assessing antiviral drugs efficacy is reverse transcription-quantitative real-time PCR. However, the application is limited on account of high reagent costs, complex time-consuming operations and long detection time. Aptamers have been widely applied in application of pathogens or diseases diagnosis and treatments because of high specificity, strong affinity, good stability, easy synthesized and low costs. This study aimed to establish an aptamer (GBN34)-based high-throughput screening (GBN34-AHTS) model for efficient selection and evaluation of natural ingredients against NNV infection. GBN34-AHTS is an expeditious rapid method for selecting natural ingredients against NNV, which is characterized with high-speed, dram, sensitive and accurate. AHTS strategy could reduce work intensity and experimental costs and shorten the whole screening cycle of effective ingredients. AHTS should be suitable for rapid selection of effective ingredients against other viruses, which is important for improving the prevention and controlling of aquatic diseases.

Antiviral Activities of Green Tea Components against Grouper Iridovirus Infection In Vitro and In Vivo.

(1) Background: Singapore grouper iridovirus (SGIV) can cause extensive fish deaths. Therefore, developing treatments to combat virulent SGIV is of great economic importance to address this challenge to the grouper aquaculture industry. Green tea is an important medicinal and edible plant throughout the world. In this study, we evaluated the use of green tea components against SGIV infection. (2) Methods: The safe working concentrations of green tea components were identified by cell viability detection and light microscopy. Additionally, the antiviral activity of each green tea component against SGIV infection was determined with light microscopy, an aptamer (Q5c)-based fluorescent molecular probe, and reverse transcription quantitative PCR. (3) Results: The safe working concentrations of green tea components were green tea aqueous extract (GTAE) ≤ 100 µg/mL, green tea polyphenols (TP) ≤ 10 µg/mL, epigallocatechin-3-gallate (EGCG) ≤ 12 µg/mL, (-)-epigallocatechin (EGC) ≤ 10 µg/mL, (-)-epicatechin gallate (EGC) ≤ 5 µg/mL, and (-)-epicatechin (EC) ≤ 50 µg/mL. The relative antiviral activities of the green tea components determined in terms of MCP gene expression were TP > EGCG > GTAE > ECG > EGC > EC, with inhibition rates of 99.34%, 98.31%, 98.23%, 88.62%, 73.80%, and 44.31%, respectively. The antiviral effect of aptamer-Q5c was consistent with the results of qPCR. Also, TP had an excellent antiviral effect in vitro, wherein the mortality of fish in only the SGIV-injection group and TP + SGIV-injection group were 100% and 11.67%, respectively. (4) Conclusions: In conclusion, our results suggest that green tea components have effective antiviral properties against SGIV and may be candidate agents for the effective treatment and control of SGIV infections in grouper aquaculture.