Influence of the organic matter on the mycobactericidal activity of five chemical disinfectants used for livestock

Abstract

The influence of the organic matter on the mycobactericidal activity of five proprietary disinfectant of veterinary use was evaluated using a 0.0005% (moist weight) suspension of Mycobacterium fortuitum; the organic matter was represented either by bovine faeces or serun. The five disinfectant products tested uere: "A" - sodiun hypochloride; "B" - amixture of phenols and cresylic acid; "C" - a mixture of aldehydes; "D" - iodophor; "E" - phenolyc compounds. The contact period of each disinfectant with the suspension of M. fortuimm in the presence of the organic matter was 60 minutes at temperature between 4 to 8 ºC. The disinfectant action was interrupted after the established time using nutrient broth containing 5% sterilized rabbit serun added with 0.05% Tween 80 for the disinfectants "C", "D" and "E"; disinfectant "B" was neutralized with nutrient broth enriched with rabbit serun added with 3.0% Tween 80; disinfectant "A" was treated by 5% sodium thiosulphate added with 0.05% Tween 80. The isolation of the viable microorganisms was carried out by culturing in the Lowenstein-Jensen medium and counting the Colonies Forming Unit (CFU). Disinfectants "A", "B" and "C" were found to be highly effective even in the presence of the serun or faeces; the percentage of the CFU reduction was above 55.0% when compared to controls. Disinfectant "D" was found to have a varied behavior with the system tested. Product "E" was found to be ineffective, without any mycobactericidal activity. Despite the high percentage of CFU reduction of above 90.0% found with product "A", the mycobactericidal activity was inhibited by both types of organic matter (Mann-Whitney U-test, α = 0.05). The efficacy of product "B" on M. fortuimm was influenced only by the presence of the bovine serum. The mycobactericidal activity of product "C" was not affected by the two type of the organic matter used in this study.