Analysis and optimization of a quantitative organic soil neutralization test for disinfectants.

An analysis and optimization of a test to quantitatively assess the resistance of disinfectants to neutralization by organic soil is presented. The recommended method uses sterile, dry baker's yeast as a standard organic soil and 24-hr cultures of Staphylococcus aureus and Pseudomonas aeruginosa as test organisms. The test determines the maximum per cent (w/v) of organic soil which a disinfectant can tolerate and remain able to kill about 106 test organisms/ml in 10 min at 25 degrees C. This per cent is defined as the organic soil neutralization number. The procedure offers several advantages over other organic soil capacity tests.