V S Springthorpe

Institutional outbreaks of rotavirus diarrhoea: potential role of fomites and environmental surfaces as vehicles for virus transmission

To assess the potential of fomites and environmental surfaces as vehicles in the transmission of rotaviral diarrhoea, disks (1 cm diameter) of various porous and non-porous materials were contaminated with about 10(5) plaque-forming units of the Wa strain of human rotavirus (HRV) suspended in faecal matter. The contaminated disks were then held for 10 days at either room temperature (22 +/- 2 degrees C) or 4 degrees C with the relative humidity (RH) at the high (85 +/- 5%), medium (50 +/- 5%) or low (25 +/- 5%) level. Survival was longer on non-porous surfaces at the lower temperature and at lower humidity. In contrast, survival on porous surfaces was very variable; better on cotton-polyester than on poster card or paper currency on which HRV survived very poorly. These results suggest that under the right environmental conditions, HRV-contaminated objects could play a role in the transmission of rotavirus infections in hospitals, nursing homes and day-care centres.

Chemical disinfection of human rotavirus-contaminated inanimate surfaces.

Fomites may play a role in the transmission of rotavirus infections, and in view of this, 27 disinfectants were evaluated for their ability to inactivate human rotavirus (HRV) on contaminated non-porous inanimate surfaces. Disks of stainless steel, glass and two types of plastics were contaminated with about 10(7) plaque-forming units of HRV suspended in faecal matter. The inoculum was allowed to dry and an equal volume of the product under test was applied to the contaminated surface. After contact for 1 min, the action of the disinfectant was stopped by dilution. Surviving infectious virus on the disks was determined by plaque assay in MA-104 cells. A product was considered to be effective if it could reduce the virus titre by at least 3 log10. Only 33.3% (9/27) of the formulations tested proved to be effective. Further testing of the effective products, which included antiseptics, instrument soaks and hard-surface disinfectants, showed that all of them could, in fact, reduce the virus titre on contaminated surfaces by at least 6 log10. These findings show the relative resistance of HRV to a wide range of chemical disinfectants in common use, and also emphasize the need for a more thorough evaluation of the virucidal potential of formulations regularly employed in attempts to prevent and control outbreaks of rotaviral diarrhoea.

Chemical disinfection of human rotaviruses: efficacy of commercially-available products in suspension tests

Suspension tests were conducted on 69 commercial and 7 non-commercial disinfectant formulations to determine which classes of chemicals were most active against human rotavirus (HRV). Virus samples, in the presence of varying levels of organic matter, were exposed to the disinfectants for 1 min. The levels of remaining infectious virus were determined by plaque assay. Products were rated by their ability to reduce the levels of infectious virus by more than 3 log10 in the presence or absence of tryptose phosphate broth (peptides and inorganic salts) or fecal matter. Of the commercially-available products tested, only 25% were rated as highly and 7% as moderately effective. The remaining 68% were either effective only in the absence of any additional organic matter (48%) or were completely ineffective (20%). The majority (64%) of the moderately and highly effective products were further examined for their ability to inactivate greater than 6 log10 of infectious HRV in the presence of fecal matter or tryptose phosphate broth. With one exception, all these products were still effective. Products potentially suitable as topical antiseptics, hard surface disinfectants and instrument soaks were identified. The results emphasize the care that should be exercised in the selection of disinfectants for the control and prevention of rotaviral infections.

A quantitative study of the survival of two species of Candida on porous and non-porous environmental surfaces and hands

Aims: In spite of the importance of many species of Candida as human pathogens, little is known about their ability to survive on animate and inanimate surfaces. Such information is essential in understanding the vehicles and modes of their spread, and in designing proper infection control strategies against them. The aim of this study was to generate comparative quantitative data in this regard.