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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
Despite the availability of a safe and effective vaccine, hepatitis B remains a globally important disease. The major routes of transmission of hepatitis B virus (HBV) are parenteral and infectivity appears to be especially related to blood, however hepatitis B is not spread exclusively by blood and blood products. It has been observed that under certain circumstances the virus is infective by mouth, that it is endemic in closed institutions and institutions for the mentally handicapped, that it is more prevalent in adults in urban communities and in poor socio-economic conditions. There is much evidence for the transmission of hepatitis B by intimate contact and by the sexual route. HBV has been found in various body fluids, such as saliva, menstrual and vaginal discharges, seminal fluid, breast milk, and serous exudates, and these have been implicated as vehicles of transmission of infection. It is not surprising therefore that contact associated hepatitis B is of major importance. Effective disinfection in institutional settings is therefore vital in preventing the spread of this highly infectious virus.
Indirect methods for measuring disinfectant activities against HBV have been developed since the virus cannot be propagated in cell culture. The most favoured method relies on the destruction of HbsAg, the surface antigen of HBV, (Destruction of the antigenicity and effect on the immunochemical reactivity of antigens of the hepatitis B virus (HbsAg, HbcAg and HbeAg) by disinfectants – a test model. Frosner, Jentsch and Uthemann Zbl.Bakt. Hyg., I Abt. Orig.B 176; 1, 1982). This method is recommended by the German Association for the Control of Viral Diseases rather than methods such as the demonstration of destruction of HBV DNA polymerase or the MADT (Morphological alteration and disintegration test). It is favoured for the following reasons:
1 HbsAg is the virus receptor which makes selective infection of liver cells possible. Destruction of HbsAg should thus result in the loss of viral infectivity.
2 Destruction of virus DNA polymerase is not sufficiently sensitive since sera that are DNA polymerase negative can also e HBV positive and infectious.
3 The antigen inactivation method usually makes greater demands on the concentration or contact time of the biocide than the alternative indirect methods.
Destruction of HbsAg is demonstrated in this test by the loss of immunological reactivity of a high titre HbsAg positive serum following exposure to the biocide as measured by an enzyme immuno-assay (EIA). A disinfectant is only assumed to be effective against HBV in the antigen inactivation tests if there is complete destruction of the antigenicity of the HbsAg.
PROTOCOL AND RESULTS
10µl of HBV 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 water to act as a positive control. These exposures of HBV to D-Stroy/Activ8 were performed at room temperature (~21°C) for a contact time of 5 minutes and 15 minutes.
Following the timed HBV exposures, dilutions of the biocide/serum mix were made in calf serum, to give 1:10, 1:100, 1:1000 dilutions. These dilutions were tested for the presence of residual HbsAg (hepatitis B surface antigen) by using a commercial enzyme immuno-assay according to the manufacturers instructions and also including the manufacturers controls. Results are reported in units of absorbance at 450mm.
5 MINUTE EXPOSURE TO HBV
| Dilution in calf serum |
D-Stroy/Activ8 1st |
D-Stroy/Activ8 2nd |
Water |
| 1:10 |
0.208 |
0.170 |
1.071 |
| 1:100 |
0.066 |
0.075 |
0.181 |
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1:1,000
|
0.042
|
1.050
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0.059
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15 MINUTE EXPOSURE TO HBV
| Dilution in calf serum |
D-Stroy/Activ8 1st |
D-Stroy/Activ8 2nd |
Water |
| 1:10 |
0.203 |
0.132 |
1.205 |
| 1:100 |
0.064 |
0.052 |
0.196 |
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1:1,000
|
0.044
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1.040
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0.059
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Values in bold are considered positive for the detection of HbsAg. Any readings less than 0.123 (assay cut-off value) are considered to have no viral protein present.
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