Detection of virulence, antimicrobial resistance, and heavy metal resistance properties in Vibrio anguillarum isolated from mullet (Mugil cephalus) cultured in Korea.

In the present study, we identified and characterized 22 strains of V. anguillarum from 145 samples of mullets (Mugill cephallus) cultured in several fish farms in South Korea. They were subjected to pathogenicity tests, antimicrobial susceptibility test, and broth dilution test to detect virulence markers, antimicrobial resistance, and heavy metal resistance properties. All the isolates showed amylase and caseinase activity, followed by gelatinase (90.9%), DNase (45.5%), and hemolysis activities (α = 81.1% and ß = 18.2%). The PCR assay revealed that isolates were positive for VAC, ctxAB, AtoxR, tdh, tlh, trh, Vfh, hupO, VPI, and FtoxR virulence genes at different percentages. All the isolates showed multi-drug resistance properties (MAR index ≥ 0.2), while 100% of the isolates were resistant to oxacillin, ticarcillin, streptomycin, and ciprofloxacin. Antimicrobial resistance genes, qnrS (95.5%), qnrB (86.4%), and StrAB (27.3%), were reported. In addition, 40.9% of the isolates were cadmium-tolerant, with the presence of CzcA (86.4%) heavy metal resistance gene. The results revealed potential pathogenicity associated with V. anguillarum in aquaculture and potential health risk associated with consumer health.

Biofilm formation of pathogenic bacteria isolated from aquatic animals.

Bacterial biofilm formation is one of the dynamic processes, which facilitates bacteria cells to attach to a surface and accumulate as a colony. With the help of biofilm formation, pathogenic bacteria can survive by adapting to their external environment. These bacterial colonies have several resistance properties with a higher survival rate in the environment. Especially, pathogenic bacteria can grow as biofilms and can be protected from antimicrobial compounds and other substances. In aquaculture, biofilm formation by pathogenic bacteria has emerged with an increased infection rate in aquatic animals. Studies show that Vibrio anguillarum, V. parahaemolyticus, V. alginolyticus, V. harveyi, V. campbellii, V. fischeri, Aeromonas hydrophila, A. salmonicida, Yersinia ruckeri, Flavobacterium columnare, F. psychrophilum, Piscirickettsia salmonis, Edwardsiella tarda, E. ictaluri, E. piscicida, Streptococcus parauberis, and S. iniae can survive in the environment by transforming their planktonic form to biofilm form. Therefore, the present review was intended to highlight the principles behind biofilm formation, major biofilm-forming pathogenic bacteria found in aquaculture systems, gene expression of those bacterial biofilms and possible controlling methods. In addition, the possibility of these pathogenic bacteria can be a serious threat to aquaculture systems.

Virulence and antimicrobial resistance potential of Aeromonas spp. associated with shellfish.

Aeromonas spp. are associated with seafood-related outbreaks worldwide. In seafood industry, shellfish play a major role in global seafood production. With this emerging trend of shellfish consumption, shellfish-related bacterial infections are being reported frequently. Aeromonas spp. are natural contaminants found in shellfish. Although 36 species have been identified, some species including Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii biotype sobria have dragged major attention as foodborne pathogenic bacteria. The ability to elaborate a variety of virulence factors of Aeromonas spp. contributes to the pathogenic activities. Also, emerging antimicrobial resistance in Aeromonas spp. has become a huge challenge in seafood industry. Furthermore, multidrug resistance increases the risk of consumer health. Studies have supplied pieces of evidence about the emerging health risk of Aeromonas spp. isolated from seafood. Therefore, the present review was intended to highlight the prevalence, virulence and antimicrobial resistance of Aeromonas spp. isolated from various types of shellfish.

Binary counter ion effects and dielectric behavior of iodide ion conducting gel-polymer electrolytes for high-efficiency quasi-solid-state solar cells.

A series of highly efficient quasi-solid-state dye-sensitized solar cells (DSCs) is prepared by harnessing the binary cation effect and positive effects of the selected performance enhancers of gel-polymer electrolytes. The new electrolyte is composed of polyacrylonitrile polymer, tetra-hexylammonium iodide (Hex4NI) and KI binary salts as well as 4-tertbutylpyridine and 1-butyl-3-methylimidazolium iodide performance enhancers. The charge transport in the series of electrolytes is thermally activated and, accordingly, the temperature dependence of conductivity follows the VTF behavior. The enhancement of conductivity is observed with an increasing mass fraction of KI and decreasing mass fraction of Hex4NI, while the total mass fraction of salts in the electrolyte is kept unchanged. The highest conductivity of 3.74 mS cm-1 at ambient temperature is shown by the sample containing KI only (without Hex4NI) at all the temperatures. The effects of dielectric polarization of the electrolytes are studied by analyzing the frequency dependence of the real and the imaginary parts of the AC conductivity in detail. Appropriate and reproducible cell construction are assured by efficiencies of above 5% exhibited by all the quasi-solid-state DSCs assembled using double-layered TiO2 photo-electrodes and the new electrolyte series. Besides, highlighting the mixed cation effect, the cells with mixed salts exhibited efficiencies greater than 6%. An impressively high efficiency of 7.36% was shown by the DSC prepared with electrolyte containing 75 wt% KI and 25 wt% Hex4NI. This study reveals that the salt combination of KI and Hex4NI, which has not been reported before, is a suitable binary iodide salt mixture to prepare highly efficient DSCs. The replacement of tetra-hexylammonium ions by K+ ions improves the charge transport in the electrolyte; however, the best solar cell performance is shown by the mixed salt system with 75 wt% KI and 25 wt% Hex4NI, which is not the highest conductivity composition. Therefore, the exhibited high efficiency of 7.36% is evidently due to the binary cation effect.

Host-vector interaction in dengue: a simple mathematical model

Introduction: Dengue is a mosquito-borne viral infection endemic in tropical and subtropical regions, now spreading at epidemic proportions causing a major health issue in Sri Lanka and elsewhere. No effective vaccine or a curative antiviral drug is available to prevent or treat the disease. The only way of mitigating dengue at present, is through mosquito eradication and educating the public on preventive measures which can minimizing the cycle of transfer. Objectives: A theoretical model of dengue with simple mathematics is presented to gain a quantitative understanding of the pattern of dengue outbreaks in Sri Lanka and suggest control measures. Methods: The statistics on incidence of the disease reported by the Epidemiology Unit is analyzed using the model. Despite simplicity, the model possesses explanatory and predictive capacity, enabling determination of crucial parameters. The model shows that the "infectives" increase exponentially in an outbreak, provided the number of vectors per human exceeds a threshold, illustrating not only vector eradication but measures which minimize their biting frequency and preventing prolonged survival are effective safeguards. Results: In a population consisting of 75% who are susceptible, the threshold is estimated to be 20 mosquitos per person. Conclusions: The model showed that the endemic equilibrium of the system can occur at any level. As demographic changes escalate mosquito breeding, they infect more and more susceptible people. The consequent increase in virus replication induces new strains broadening the genetic diversity of the virus and helping it to overcome the human immune response. The increasing endemicity of dengue due to this is demonstrated by the model.