Efficiency of four currently used decontamination conditionings in Romania against Aspergillus and Candida strains

Efficacy of four commercial biocidal products (noted A to D), using manufacturers' recommendations, and a contact time of 30minutes, were evaluated in the purpose of standard SR EN1657: 2006 adapted.

Were used four strains, two as reference: Aspergillus brasiliensis (niger) (ATCC 16404) and Candida albicans (ATCC 10231), and two isolates: Aspergillus flavus and respectively Aspergillus fumigatus. The inoculum plates containing Malt Extract Agar (MEA) were incubated 48h for C. albicans and 72hours for Aspergillus spp. The standard SR EN1657: 2006 adapted was conducted in two phases: the test cultures preparation and the method validation. Method validation included: the control of experimental conditions and of neutralizant solution, and the method verification.

Results revealed that three from the four tested products (A, B and D) had exerted biocidal effect on the studied strains at the recommended concentrations, the registered CFU values being reduced by more than 4 log₁₀, conversely in the case of the product (C), applied against A. fumigatus at the recommended concentration of 2%, the biocidal effect was not detected, fact confirmed also by the CFU's value (3.59 log₁₀). The biocide retested at a greater concentration (of 5%), showed a biocidal effect against A. fumigatus after 30minutes, the CFU value being reduced, by more than 5.29 log₁₀, evidencing the resistance emergence of A. fumigatus under the repeated pressure of biocides.

It is re-confirming that merely the "chemical" defense measures to defuse the fungi's strategies become unproductive.