Recovery of Gram-Positive Cocci and Candida albicans from Peroxygen/Silver-Based Disinfectants

Neutralization method evaluation is an important first step in a disinfectant validation study program. It is also crucial in assessment of the efficiency of microbial recovery media in the presence of a residual biocidal agent. In the present study, four commercially available peroxygen/silver-based disinfectant formulae – intended to be used in a pharmaceutical facility sanitization program – were tested at two dilutions against three Gram-positive cocci and one yeast; Staphylococcus aureus (ATCC 6538), Kucoria rhizophila (ATCC 9341) and Candida albicans (ATCC 10231) and Staphylococcus capitis as an environmental monitoring (EM) isolate sample (identified by miniaturized biochemical identification system). Disinfectants preparation, dilutions and the test procedure were carried on in laboratory under conditions simulating the working environment of 20–25°C and RH% 40–60. In-house made neutralizing broth was mixed with biocidal agents to make two dilutions of each disinfectant forming Peroxygen: neutralizing broth ratios of 1:10 and 1:100 (v/v). Three populations were established and two comparison ratio groups were examined, namely neutralizer efficacy and neutralizer toxicity. Two acceptance criteria were tested. One criterion showed higher rate of neutralization success than the other. S. aureus showed the highest rate of successful microbial recovery from neutralization process. The Disinfectant (Bixco) was exceptionally neutralized at all dilutions with all microorganisms. In conclusion, in-house made neutralizing broth effectively neutralized all disinfectants with all the tested microorganisms at 1:100 (v/v); thus, it can be used in sanitizer validation studies and EM media.