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There was no significant difference between a 5 minute and 15 minute exposure in the level of HBV surface antigen detected by this assay, and therefore a minimal exposure of 5 minutes appears to have the desired result of destroying Hepatitis B virus surface antigen. After exposure to HBV both samples of D-Stroy/Activ8 had a similar effect upon the virus in that:
• Residual HBV detected in a 1:10 dilution of calf serum was reduced substantially from the water control.
• No residual HBV was detected in subsequent dilutions of 1:100, biocide/HBV:calf serum
LIMITATIONS OF USE IN THIS STUDY AND INFORMATION
As Micropathology Ltd has no control over the usage of this biocide material, the testing described in this report does not constitute an endorsement of this product by Micropathology Ltd in any application. Whilst Micropathology Ltd has tested this material in the manner indicated, the Company specifically excludes any reference to its name in any literature as promotional material related to any product.
INTRODUCTION
Infection with hepatitis C virus (HCV) occurs to varying degrees around the world. Its prevalence in Western Europe is estimated by the World Health Organisation at being 1-2.4% of the general population. In certain population groups however, such as those with a current or past history of intravenous drug use, the incidence of infection is much higher.
HCV can cause chronic disease which is difficult to treat and vaccination has yet to be developed. The virus may persist at a high concentration for many years in the bloodstream of infected individuals and has also been detected in other types of body fluids. Therefore its control is of importance in any situation where people are exposed to spillages of blood and possibly other body fluids.
Difficulties exist in measuring the effectiveness of disinfectants against the virus HCV cannot be grown in the laboratory and the only animal model is the chimpanzee. Viral nucleic acid is usually readily detectable in the serum of chronically infected patients, often at high titres. Therefore the only practicable source of virus-specific molecules on which to base an indirect method of measuring the effectiveness of disinfectants against the virus is the blood of viraemic patients. This protocol uses an assay for measuring the concentration of the viral nucleic acid (which in the case of HCV is RNA) in serum following exposure of the sample to the disinfectant, and to distilled water as a control. The loss of detectable viral RNA is used as a marker of virus ‘killing’. The assay is likely to underestimate the effectiveness of disinfectants against HCV because the RNA molecule is apparently relatively resistant to chemical degradation and virus inactivation will occur through protein destruction before RNA is affected, whereas the protein may not be so resistant. Viral RNA is, however, essential for infectivity and so its disappearance following exposure to a disinfectant is an absolute indication of virus inactivation.
PROTOCOL AND RESULTS
D-Stroy/Activ8 was tested using this viral degradation assay. The source of the HCV RNA for this test was two patients with well-documented chronic hepatitis C infection. The sera had a high titre of HCV RNA previously measured at 500,000 and 50,000 HCV RNA copies/ml. 10µl of HCV positive serum (either 500,000 or 50,000 HCV RNA copies/ml) was added to each of two 990µl samples of D-Stroy/Activ8 (diluted to a working solution of 1 part biocide to 9 parts water as directed), or to 990µl of distilled water to act as a positive control. These treatments were performed at room temperature (approximately 21°C for a contact time of 5 minutes and 15 minutes. As extraction procedure was used to isolate viral RNA from the solution. Residual disinfectant was removed at this stage.
The concentration of remaining detectable viral RNA was measure using a very sensitive quantitative assay, the results of which are expressed as copies of RNA detected per milliliter (HCV RNA copies/ml)
The ideal situation is that under this protocol a disinfectant must be able to reduce the concentration of HCV RNA to an undetectable level.
However this experiment has shown that the biocides used here do reduce the level of RNA considerably and therefore act as virucidal agents.
No satisfactory difference in the level of HCV RNA detected at an exposure of 5 minutes was observed between the water control and both samples of D-Stroy/Activ8 tested here, with an exposure to serum with a concentration of 500,000 HCV RNA copies/ml. However, after 15 minutes of exposure to the biocide, HCV RNA was undetectable. After exposure to serum with a lower concentration of HCV (50,000 HCV RNAcopies/ml) both samples of D-Stroy/Activ8 were observed to eradicate all HCV RNA after exposure of 5 and 15 minutes.
In conclusion D-Stroy/Activ8 can be considered an effective biocide against Hepatitis C virus RNA in low concentrations and also with at least a 15 minute exposure time, to higher concentrations of the virus.
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