Suitable Disinfectants with Proven Efficacy for Genetically Modified Viruses and Viral Vectors.

Viral disinfection is important for medical facilities, the food industry, and the veterinary field, especially in terms of controlling virus outbreaks. Therefore, standardized methods and activity levels are available for these areas. Usually, disinfectants used in these areas are characterized by their activity against test organisms (i.e., viruses, bacteria, and/or yeasts). This activity is usually determined using a suspension test in which the test organism is incubated with the respective disinfectant in solution to assess its bactericidal, yeasticidal, or virucidal activity. In addition, carrier methods that more closely reflect real-world applications have been developed, in which microorganisms are applied to the surface of a carrier (e.g., stainless steel frosted glass, or polyvinyl chloride (PVC)) and then dried. However, to date, no standardized methods have become available for addressing genetically modified vectors or disinfection-resistant oncolytic viruses such as the H1-parvovirus. Particularly, such non-enveloped viruses, which are highly resistant to disinfectants, are not taken into account in European standards. This article proposes a new activity claim known as "virucidal activity PLUS", summarizes the available methods for evaluating the virucidal activity of chemical disinfectants against genetically modified organisms (GMOs) using current European standards, including the activity against highly resistant parvoviridae such as the adeno-associated virus (AAV), and provides guidance on the selection of disinfectants for pharmaceutical manufacturers, laboratories, and clinical users.

Surface-Dried Viruses Can Resist Glucoprotamin-Based Disinfection.

Touching of contaminated objects and surfaces is a well-known method of virus transmission. Once they are attached to the hands, viruses can easily get adsorbed and initiate infection. Hence, disinfection of frequently touched surfaces is of major importance to prevent virus spreading. Here we studied the antiviral activity of a glucoprotamin-containing disinfectant against influenza A virus and the model virus vaccinia virus (VACV) dried on inanimate surfaces. The efficacy of the surface disinfectant on stainless steel, polyvinyl chloride, and glass coupons was investigated in a quantitative carrier test. Vacuum-dried viruses were exposed to 0.25%, 0.5%, and 1% disinfectant for 5 min, 15 min, and 30 min without agitation, and residual infectivity was determined by endpoint titration. Although glucoprotamin was highly active against both viruses in suspension, limited antiviral activity against the surface-dried viruses was detected. Even after 30 min of exposure to 1% disinfectant, VACV was not completely inactivated. Furthermore, influenza A virus inactivation was strongly affected by the surface composition during the 5-min and 15-min treatments with 0.25% and 0.5% disinfectant. The results presented in this study highlight the relevance of practical tests to assess the antiviral activity of surface disinfectants. High virucidal activity in solution is not necessarily indicative of high antiviral activity against surface-dried viruses. In addition, we want to emphasize that the mere exposure of surfaces to disinfectants might not be sufficient for virus inactivation and mechanical action should be applied to bring attached viruses into contact with virucidal compounds.

Evaluation of a virucidal quantitative carrier test for surface disinfectants.

Surface disinfectants are part of broader preventive strategies preventing the transmission of bacteria, fungi and viruses in medical institutions. To evaluate their virucidal efficacy, these products must be tested with appropriate model viruses with different physico-chemical properties under conditions representing practical application in hospitals. The aim of this study was to evaluate a quantitative carrier assay. Furthermore, different putative model viruses like adenovirus type 5 (AdV-5) and different animal parvoviruses were evaluated with respect to their tenacity and practicability in laboratory handling. To evaluate the robustness of the method, some of the viruses were tested in parallel in different laboratories in a multi-center study. Different biocides, which are common active ingredients of surface disinfectants, were used in the test. After drying on stainless steel discs as the carrier, model viruses were exposed to different concentrations of three alcohols, peracetic acid (PAA) or glutaraldehyde (GDA), with a fixed exposure time of 5 minutes. Residual virus was determined after treatment by endpoint titration. All parvoviruses exhibited a similar stability with respect to GDA, while AdV-5 was more susceptible. For PAA, the porcine parvovirus was more sensitive than the other parvoviruses, and again, AdV-5 presented a higher susceptibility than the parvoviruses. All parvoviruses were resistant to alcohols, while AdV-5 was only stable when treated with 2-propanol. The analysis of the results of the multi-center study showed a high reproducibility of this test system. In conclusion, two viruses with different physico-chemical properties can be recommended as appropriate model viruses for the evaluation of the virucidal efficacy of surface disinfectants: AdV-5, which has a high clinical impact, and murine parvovirus (MVM) with the highest practicability among the parvoviruses tested.

Can vaccinia virus be replaced by MVA virus for testing virucidal activity of chemical disinfectants?

BACKGROUND: Vaccinia virus strain Lister Elstree (VACV) is a test virus in the DVV/RKI guidelines as representative of the stable enveloped viruses. Since the potential risk of laboratory-acquired infections with VACV persists and since the adverse effects of vaccination with VACV are described, the replacement of VACV by the modified vaccinia Ankara strain (MVA) was studied by testing the activity of different chemical biocides in three German laboratories. METHODS: The inactivating properties of different chemical biocides (peracetic acid, aldehydes and alcohols) were tested in a quantitative suspension test according to the DVV/RKI guideline. All tests were performed with a protein load of 10% fetal calf serum with both viruses in parallel using different concentrations and contact times. Residual virus was determined by endpoint dilution method. RESULTS: The chemical biocides exhibited similar virucidal activity against VACV and MVA. In three cases intra-laboratory differences were determined between VACV and MVA - 40% (v/v) ethanol and 30% (v/v) isopropanol are more active against MVA, whereas MVA seems more stable than VACV when testing with 0.05% glutardialdehyde. Test accuracy across the three participating laboratories was high. Remarkably inter-laboratory differences in the reduction factor were only observed in two cases. CONCLUSIONS: Our data provide valuable information for the replacement of VACV by MVA for testing chemical biocides and disinfectants. Because MVA does not replicate in humans this would eliminate the potential risk of inadvertent inoculation with vaccinia virus and disease in non-vaccinated laboratory workers.