Virucides

Bactericide, fungicide, virucide,proto acide, andalgicide are chemical agents that kill either bacteria, fungi (including yeasts), vimses, protozoa, or algae. They may... 

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. 

Isopropyl alcohol (isopropanol, CH3CHOH.CH3) has slightly greater bactericidal activity than that of ethanol but is also about twice as toxic. It is less active against viruses, particularly non-enveloped viruses, and should be considered a limited-spectrum virucide. Used at concentrations of 60-70%, it is an acceptable alternative to ethanol for preoperative skin treatment and is also employed as a preservative for cosmetics. 

Virucide (viricide). An agency which kills viruses. 

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. 

For assaying herpes virus, monolayers of baby hamster kidney (BHK) cells are used. Virus titre is expressed as the number of plaque-forming units (pfu) per millilitre before and after exposure to a disinfectant, so that the virucidal efficacy of the test agent can be determined. A diagrammatic representation is given in Fig. 11.7. 

This type of procedure may thus suggest that an unnecessarily high disinfectant concentration (so-called overkill) may be employed in practice to achieve a virucidal effect. 

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. 

A model for evaluating virucidal agents has been described which employs... 

Jones M.V., Bellamy K., Alcock R. Hudson R. (1991) The use of bacteriophage MS2 as a model system to evaluate virucidal hand disinfectants. JHosp Infect, 17, 270-285. 

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. 

Although many papers have been published on the virucidal (viricidal) activity of biocides there is little information available about the uptake of bioeides and their penetration into viruses of different types, or of their interaction with viral protein and nucleic acid. 

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. 

Malik, Y. S. and Goyal, S. M. (2006). Virucidal efficacy of sodium bicarbonate on a food contact surface against feline caUcivirus, a norovirus surrogate. Int. ]. Food Microbiol. 109, 160-163. 

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. 

Whitehead, K. and McCue, K. A. (2010). Virucidal efficacy of disinfectant actives against feline calicivirus, a surrogate for norovirus, in a short contact time. Am. J. Infect. Control 38, 26-30. 

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. 

If the biter is human immunodeficiency virus positive, the victim should have a baseline human immunodeficiency virus status determined and then repeated in 3 and 6 months. The bite should be thoroughly irrigated with a virucidal agent such as povidone-iodine. Victims may be offered antiretroviral chemoprophylaxis. 

Condom, diaphragm, or cervical cap with contraceptive or antimicrobial agent (including virucidal) agent. 

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. 

Activity spectrum. Disinfectants inactivate bacteria (gram-positive > gram-negative > mycobacteria), less effectively their sporal forms, and a few (e.g, formaldehyde) are virucidal. 

Docosanol is not directly virucidal instead, it blocks the entry of the virion into the host cell by inhibiting the fusion of the viral envelope with the host plasma membrane. Because it does not affect viral replication or protein production, it may be less susceptible to the development of resistance than other antiviral drugs. 

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