Bacterial vs. fungal spore resistance to peroxygen biocide on inanimate surfaces

A sporicidal agent formula based on a mixture of peroxyacetic acid and hydrogen peroxide was assessed for its efficacy on a representative sample of vinyl surface material. Vinyl is the construction material of wall and floor lining in pharmaceutical plants. The experimental manipulations; applied herein, simulated the actual biocidal agent preparation and were carried out using USP purified water, test temperature was 20–25 °C, RH% was 40–60% and pH was 3.08 and 2.86 for 1% and 2% (v/v) respectively. Following the selection of the optimum method of antimicrobial activity neutralization, two disinfectant concentrations were examined for their sporicidal activity. The results of carrier test revealed that the disinfectant concentration (2%) (v/v) was significantly effective as a sporicidal agent after 5 and 10 min for Aspergillus brasiliensis and Bacillus subtilis subsp. spizizenii, respectively, while the concentration of 1% (v/v) did not achieve even one logarithmic reduction after 20 min. The agent was able to achieve more than 100 times reduction from the initial bioburden on the surfaces when used in the concentration of 2% (v/v) after 10 min of contact time. The ideal kinetics of microbial death usually follows 2 parts (by averaging the responses with time for the 3 replicates): initial slow rate of death followed by higher rate. The initial sigmoidal part was only observed with B. subtilis upon exposure to 2% (v/v) sporicidal agent. Elimination time for B. subtilis spores was 15 min which was about double the time required for eradication of A. brasiliensis.