[Methods for testing surface disinfection procedures under current conventional conditions].

Abstract

A method of testing surface disinfection procedures is described with which the same conditions are maintained as those encountered in practice. The disinfectant is applied to surfaces in a conventional manner at a natural scale. A standardised wet-mopping procedure (two-bucket method) applied to floors of glazed clinker serves as a reference. The test method is quantitative. For comparison the same procedure using water of standardised hardness is used. The test parameters are the reduction of the colony count (CC) both on the surface treated and in the used washing water following certain periods of exposure to the disinfectant. For the suitability test of disinfectants the surface is contaminated with reference strains, Kl. pneumoniae ATCC 27736 and Staph. aureus Wood 46. In some special cases wild strains were used for contamination. When testing surface disinfection under user conditions, the flora settling on the surface used is investigated. The bacterial collector after Thran is employed for the extraction of the germs from the surface. Wet mopping with water of standardised hardness has already reduced the count on the floor of Kl. pneumoniae by 2.8 log on average and the count of Staph. aureus by 2.2 log. By the use of the three types of disinfectants tested the count was additionally reduced by 0.45 to 0.72 log for Kl. pneumoniae and by 1.2 to 2.2 log for Staph. aureus. Even after disinfection a spread of germs can be observed; however, it is slight and corresponds to the spread found after the use of water. After mopping with 17 degrees dH water, practically the total germ count applied is found in the cleaning water. After application of the disinfectant the germ counts for Kl. pneumoniae are reduced by 1.8 to 3.7 log and by 3.1 to 3.7 log for Staph. aureus, depending on the type of disinfectant after an exposition of 5 min in the washing water. With respect to Kl. pneumoniae, reduction of the count continues to amount to 2.7 to 3.8 log after 30 min, so that merely 20 to 30 CFU/100 ml washing water remain. The concentration of the disinfectant mainly influences the reduction of germs in the washing water. Thus the analysis of the washing water constitutes an important parameter for the evaluation of a surface disinfectant. The testing procedure proposed is very flexible as it can be readily adapted to the various disinfection problems and evaluation criteria.