Studies on the activity of surface disinfectants in the Quantitative Carrier Test.
Onderzoek naar de werkzaamheid van middelen bestemd voor oppervlaktedesinfectie volgens het voorschrift van de "Quantitative Carrier Test"
Pullen W , Klingeren B van , Verheuvel M
RIVM Report 358704002
In this report experience is descrived with a quantitative carrier test or QCT for the evaluation of surface disinfectants, that has been developed in our laboratory. the results confirm that with normal use ditlutions the threshold microbicidal effect (M.E.) value of 5 decimals reduction (D.R.), that is requested for the European Suspension Test (EST), is often not reacht`ed in the QCT. for the latter a minimum required reduction of 3 D.R., as proposed earlier (van Klingeren, 1983) is apparently more reasonable. As in the EST Treptococcus faecium was found to be more resistant tot disinfectants than S.aureaus. Agains yeast (Candida albicans and Saccharomyces cerevisiae) the proposed minimum required reduction of 3 D.R. within 15 minutes is usually attained. In experiments using relatively low concentrations of a quaternary ammonium compound and a phenolic product the microbicidal effect was not or hardly found to increase at prolonged exposure times. From the studies with ethanol and propanols it can be concluded that small amounts of 40% n-propanol, 50% 2-propanol and 60% ethanol (v/v) on surfaces rapidly kill Gram-positive and Gram-negative bacteria (> 5 D.R. in 2 minutes). Finally the tuberculocidal effect of Lyorthol, active chlorine and formaldehyde in the QCT was tested against Mycobacterium terrae as a representative testorganism showing similar resistance to disinfectants as M.tuberculosis. We conclude that the experiments described and discussed in this report confirm that the present Quantitative Carrier Test allow the reproducable evaluation of the microbicidal activity of disinfectants under circumstances simulating practical conditions.