Virucidal activity

Viruses that contain hpid are inactivated by organic solvents such as chloroform and ether. Those without hpid are resistant to these agents. This distinction has been used to classify virases. Many of the chemical disinfectants used against bacteria, e.g. phenols, alcohols and quaternary ammonium compounds (Chapter 10), have minimal virucidal activity. The most generally active agents are chlorine, the hypochlorites, iodine, aldehydes and ethylene oxide. 

The virucidal activity of chemicals is difficult to determine in the laboratory. Tissue culture techniques are the most common methods for growing and estimating viruses however, antimicrobial agents may also adversely affect the tissue culture see also Chapter 11. 

The testing of disinfectants for virucidal activity is not an easy matter. As pointed out earlier (Chapter 3), viruses are unable to grow in artificial culture media and thus some other system, usually employing living cells, must be considered. One such example is tissue culture, but not all virus types can propagate under such circumstances and so an alternative approach has to be adopted in specific instances. The principles of such methods are given below. 

Fig. 11.7 A, diagrammatic representation of plaque assay for evaluating virucidal activity and B, monolayers of baby hamster ki(hiey (BHK) cells C, virus tte untreated virus (o represents a plaque-forming unit, pfu, in BHK cells) D, virus titre disinfectant-treated virus (before plating onto BHK, die disinfectant must be neuh alized in an appropriate manner). Note the greatly reduced nimiber of pfu in D, indicative of fewer iminactivated virus particles than in C. 

The serum from patients with clinical symptoms of hepatitis B commonly contain three distinct structures that possess HBsAg (section 3.8.5 above). The effects of different concentrations of various disinfectants on the structure of Dane particles have been studied, but it is unlikely that morphological changes can be related to virucidal activity. 

Tyler R. Ayliffe G.A.J. (1987) A surface test for virucidal activity of disinfectants preliminary study with herpes virus. J Hasp Infect, 9, 22-29. 

Jimenez, L. and Chiang, M. (2006). Virucidal activity of a quaternary ammonium compound disinfectant against feline calicivirus A surrogate for norovirus. Am. J. Infect. Control 34, 269-273. 

Steinmann, J., Becker, B., Bischoff, B., Paulmann, D., Friesland, M., Pietschmann, T., Steinmann, J., and Steinmann, E. (2010). Virucidal activity of 2 alcohol-based formulations proposed as hand rubs by the World Health Organization. Am. ]. Infect. Control. 38, 66-68. 

Zoni, R., Zanelli, R., Riboldi, E., Bigliardi, L., and Sansebastiano, G. (2007). Investigation on virucidal activity of chlorine dioxide. Experimental data on feline calicivirus, HAV and Coxsackie B5. J. Prev. Med. Hyg. 48, 91-95. 

Schinazi RF, Sijbesma RP, Srdanov G, Hill CL, Wudl F (1993) Synthesis and virucidal activity of a water soluble, configurationally stable, derivatized C60 fullerene. Antimicrob. Agents Chemother. 37 1707-1710. 

Tang J, Colacino JM, Larsen SH, Spitzer W. Virucidal activity of hypericin against enveloped and non-enveloped DNA and RNA viruses. Antiviral Res 1990 13(6) 313-325. 

Comparison of the activity of sulfated homopolysaccharides such as dextran and cellulose esters with that of neutral homopolysaccharides and sulfated heteropolysaccharides such as heparin and heparan sulfuric acid half esters shows potent virucidal activity against human T-cell lymphotropic virus type III (HTLV-III) for the sulfated homopolysaccharides. In contrast, neutral homopolysaccharides have no effect and sulfated heteropolysaccharides exhibit only a little effect on HTLV-III activities. This suggests that the sulfate moiety and the type of polysaccharide are most important in inhibiting growth of HTLV-III [126]. 

Each cytotoxicity control mixture (above) was challenged with low titer stock virus to determine the dilution of test substance at which virucidal activity, if any, was retained. Dilutions that showed virucidal activity will not be considered in determining reduction of the virus by the test substance. 

As previously described, 0.1 ml of each test and control parameter following the exposure period was added to a 0.9 ml aliquot of neutralizer followed immediately by 10-fold serial dilutions in test medium to stop the action of the test substance. To determine if the neutralizer chosen for the assay was effective in diminishing the virucidal activity of the test substance, low titer stock virus was added to each dilution of the test substance-neutralizer mixture. This mixture was assayed for the presence of virus (neutralization control above). 

A number of substances have been identified that have either a specific virucidal effect on HIV or prevent infection of cells in vitro. The virucidal activity of potential topical agents can be assessed against cell-free and cell-associated virus using these assay systems. They allow the measurement of precise contact times between the HIV and virucides, enable the protective effect of preparations to be examined, and allow removal of the virucide from the system prior to assessment of cell viability. 

Assay for Determining Virucidal Activity Using Cell-Free Viruses 2.1. Materials... 

Kramer, A., Galabov, A.S., Sattar, S.A., Dohner, L., Pivert, A., Payan, C., Wolff, M.H., Yilmaz, A., and Steinmann, J., 2006. Virucidal activity of a new hand disinfectant with reduced ethanol content comparison with other alcohol-based formulations. J. Hosp. Infect., 62 98—106. 

Wutzler, P., and Sauerbrei, A., 2004. Virucidal activity of the new disinfectant monopercitric acid. Letters Appl. Microbiol., 39 194-198. 

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