FEASIBILITY OF A COMBINED CARRIER TEST FOR DISINFECTANTS - STUDIES WITH A MIXTURE OF 5 TYPES OF MICROORGANISMS

Background: There is mounting concern regarding the efficacy of many g ermicides on the market because officially recognized germicidal tests for various classes of microorganisms vary widely and often lack repr oducibility and proper quantitation. We report here a carrier method f or simultaneously and quantitatively assessing the efficacy of liquid chemical germicides against a mixture of microorganisms of varying deg rees of resistance. Methods: In the test, each small glass cup (10 mm wide x 14 mm long) was contaminated with 10 mul of a standardized mixt ure of Staphylococcus aureus, Mycobacterium bovis bacille Calmette-Gue rin, Trichophyton mentagrophytes spores, Sabin poliovirus type 1, and Bacillus stearothermophilus spores in 5% fetal bovine serum. The inocu lum was dried for 60 minutes under ambient conditions and covered with 60 mul of the disinfectant under test or a balanced salt solution con trol for the desired contact time. The carrier was then placed in 2940 mul of an eluent and the eluates assayed separately for the five micr oorganisms. Tap water was used to dilute the test product as needed. R esults: Of the 11 products tested, 2% alkaline glutaraldehyde, 0.6% so dium hypochlorite (about 5000 ppm free chlorine), and a 0.4% quarterna ry ammonium compound containing 23% hydrochloric acid were effective a gainst all five challenge organisms. A hard-surface spray containing 0 .1% o-phenylphenol with 79% ethanol was effective against all but bact erial spores; 70% (volume/volume) ethanol alone and povidone-iodine (1 % available iodine) were effective against S. aureus, the mycobacteriu m, and the fungus; a 3% solution of peroxygen compounds was effective only against S. aureus and the poliovirus; 1.5% chlorhexidine gluconat e, 0.06% quaternary ammonia compound, and 0.03% o- phenylphenol + 0.03 % p-tertiary amylphenol could inactivate nothing but S. aureus; and 3% hydrogen peroxide was ineffective in all tests. Conclusions: This met hod shows promise for use with various classes of microorganisms, indi vidually or as mixtures. Its application should enable the classificat ion of germicides according to spectrum of activity.