New method for evaluation of virucidal activity of antiseptics and disinfectants

In-vivo efficacy of hand sanitisers against feline calicivirus: a surrogate for norovirus

Hand disinfection is considered important in preventing the transmission of viruses, including norovirus. We investigated the virucidal efficacy of nine hand sanitisers (four alcohol-based sanitisers, three non-alcoholic sanitisers and two triclosan-containing antimicrobial liquid soaps) against feline calicivirus, a surrogate for norovirus, on artificially contaminated fingertips for 30 s and 2 min contact periods. Among alcohol-based sanitisers, a product containing 99.5% ethanol was more effective than those containing 62% ethanol, 70% isopropanol or 91% isopropanol. A log(10) virus reduction factor of 1.00-1.30 was achieved with 99.5% ethanol but those containing a lower alcohol concentration only achieved a log(10) reduction factor of <or=0.67. Antiseptics containing 10% povidone-iodine (equivalent to 1% available iodine) reduced virus titre by a log(10) reduction factor of 2.67 within 30s contact time. This viral reduction rate was higher than that achieved with any of the alcohol-based sanitisers, non-alcoholic sanitisers or antimicrobial soaps. The two antimicrobial soaps tested showed minimal virus reduction (a log(10) reduction factor of 0.17-0.50), which is similar to that obtained by washing hands without any soap (a log(10) reduction factor of 0.33-0.42). These results indicate that triclosan-containing antimicrobial soaps or alcohol-based hand rubs may be inadequate for preventing norovirus transmission. Further research on alternative hand sanitisers should continue for effective control of norovirus infections.

A membrane-based quantitative carrier test to assess the virucidal activity of disinfectants and persistence of viruses on porous fomites

A membrane-based quantitative carrier test method to assess the virucidal activity of disinfectants and the persistence of viruses on fomites under different environmental conditions is described. The method is based on the inactivation of the virus adsorbed to cellulose ester membranes followed by the direct enumeration of the viruses surviving the treatment without the need of an elution step. The method was suitable for four different human enteroviruses tested. Experiments comparing the infectivity loss of human enteroviruses in suspension or adsorbed to the filters after treatment with chlorine and glutaraldehyde showed that the human enteroviruses tested suffered significantly greater log10 reductions when suspended than when adsorbed. Significant differences in the effect of the disinfectants on the various human enteroviruses tested were also observed. Moreover, the procedure allowed determining the inactivation of viruses on fomites under different environmental conditions. Low temperatures and high relative humidities favored the survival of human enteroviruses. Also, viruses adsorbed to the membranes retained their infectivity frozen at -70 degrees C for more than 1 year, thus providing the possibility of preparing very simple reference materials for testing virucidal activities of antiseptics and disinfectants.