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Objectives: To establish the concentration of isopropanol that exerts the same immediate and sustained effects as n-propanol 60% v/v in surgical scrubbing, and to assess the performance of the test method proposed as the European standard in parallel experiments., Design: Isopropanol at concentrations of 70%, 80%, and 90% v/v was tested in comparison with n-propanol 60%, the proposed reference preparation, in the draft method proposed by the European standard. A Latin square design was used with four balanced blocks of five volunteers each in four experimental runs that were spaced by intervals of 1 week each. Volunteers were allotted randomly to one of the four blocks. Independently, the volunteers' right and left hands also were randomized into two groups for the assessment of either immediate or sustained effects., Setting: Two laboratories supervised by two investigators, one from Vienna, Austria, and one from London, The United Kingdom., Method: The release of skin flora from the fingertips of clean hands was assessed before and after treatment by immediate sampling from one hand and by sampling of the other, gloved hand after 3 hours. The mean log10 reductions (RF) of bacterial release achieved by rubbing the alcoholic preparations for 3 minutes onto the hands were established., Results: For both experiments, the immediate effects of isopropanol 70% (RF, 2.0 and 2.1, respectively) were significantly smaller than those of the reference n-propanol 60% (RF, 2.4 and 2.6, respectively). This also was found with the sustained effects (RF, 0.7 and 1.1 vs 1.0 and 1.6, respectively). At 90%, isopropanol equalled the immediate effect of n-propanol 60%, whereas at 80% it proved slightly (although not significantly) less active. There were no significant differences in the results of both investigators. The sustained effects of isopropanol 80% and 90% were both larger than the reference in Vienna but were found smaller by the London investigator; none of the differences were significant. Mean RFs were significantly different between Vienna and London with n-propanol 60% and isopropanol 70%, but not with isopropanol at 80% or 90%., Conclusions: At 90%, isopropanol is as effective as n-propanol 60%, which was proposed by the European Committee for Standardization as a reference in testing products for surgical hand disinfection. It could, therefore, serve as an alternative if the proposed agent is undesirable for any reason. In parallel experiments by two investigators, the proposed test method proved well workable; the results were very similar and the conclusions identical.

The efficacy of sodium hypochlorite was assessed against human immunodeficiency virus type 1 suspended in low (8% v/v) or high (80% v/v) concentrations of serum or in a high (80%) concentration of blood. In the presence of 8% serum, 100 p.p.m. available chlorine in the disinfectant test mixture inactivated 3.75 log TCID50 HIV/ml within 30 s. When the test mixture contained 80% serum, 500 p.p.m. available chlorine inactivated more than 4 log TCID50 HIV/ml in 1-2 min. Lower concentrations of available chlorine were unable to inactivate the virus completely. In the presence of 80% blood, 1000 p.p.m. available chlorine in the disinfectant test mixture was unable to inactivate 3.75 log TCID50 HIV/ml, although 2500 p.p.m. available chlorine was able to inactivate at least 1.5 log TCID50 HIV/ml. In all test mixtures, the chlorine rapidly became combined and thus less active. Our results emphasise the importance of cleaning prior to disinfection with sodium hypochlorite since it may prove to be ineffective in the presence of high levels of organic matter. In cases where prior cleaning is impossible, care must be taken to use the higher recommended concentration (a minimum of 10,000 p.p.m. available chlorine).

Alcohols are commonly used as disinfectants for skin, surfaces and immersion of some medical instruments. Measurements of the activity of alcohols against human immunodeficiency virus type 1 (HIV-1) must take account of the compatibility of neutralizers used to stop the disinfectant reaction, and of toxicity to the cell line used to detect residual virus. We have developed protocols to measure the efficacy of alcohols against HIV in suspension and dried onto surfaces in the presence of high and low protein concentrations. High titres of HIV in suspension were rapidly inactivated by 70% ethanol, independent of the protein load. When virus was dried onto a glass surface, the rate of inactivation decreased when high levels of protein were present. Due to its rapid evaporation, a spray or a wipe with alcohol cannot be guaranteed to disinfect a surface contaminated with blood or other body fluids without preliminary cleaning.