Testing chemical germicides against Candida species using quantitative carrier and fingerpad methods

Six disinfectants were tested against Candida albicans, C. parapsilosis and C. tropicalis using quantitative carrier tests based on glass (QCT-1) and metal (QCT-2) surfaces. C. albicans was also used to test four topical agents by a fingerpad method. Hard water (200 ppm as CaCO(3)) was the product diluent. In preliminary tests with QCT-1 and QCT-2, the testing was with or without a soil load; subsequent tests and fingerpad tests included soil. In QCT-1 and QCT-2, each carrier received 10 microL (5.0 x 10(6) - 1.0 x 10(7)colony forming units) of Candida, and was air dried for 1 h, then exposed to 1 mL or 50 microL of test product at 22 +/- 2 degrees C for up to 10 min. Controls received an equivalent volume of saline. For fingerpad tests, each digit received 10 microL of inoculum, which was allowed to dry and exposed to 1 mL of test product for 20 s. Inoculated plates of Sabouraud's dextrose agar were held for 48 h at 30 degrees C and colonies counted to determine reductions in colony forming units. In tests on both hard surfaces and fingerpads, ethanol and products based on ethanol reliably and rapidly inactivated all the Candida species tested. Products with sufficient potency to have tuberculocidal claims produced substantial reductions in the titre of C. albicans, although some showed a lesser reduction in titre of C. tropicalis and C. parapsilosis. This may reflect differences in cell hydrophobicity between Candida species, and highlights the need for care in selecting a suitable surrogate for disinfectant tests. The quantitative carrier and fingerpad protocols are suitable for assessing the activity of disinfectants and topical antiseptics against candida.