ABSTRACT
The mycobactericidal activity of sodium hypochlorite (2.5% of active chlorine) was evaluated against a strain of Mycobacterium bovis using the modified thin-layer Middlebrook 7H11 cultivation technique and it was compared to the test made in tubes with Stonebrink medium. The assays were performed either in the presence or absence of organic matter, at temperatures of 4° C and 21 ± 2° C. The colonycounting results were transformed into reduction percentages (Tabela 1) which were compared between the two techniques, showing the disinfectant had similar reduction percentages between plates and tubes in all conditions tested (Mann-Whitney test p < 0.05; α = 5%). The 2.5% sodium hypochlorite had a mycobactericidal activity of 100% in all conditions, except when in the presence of organic matter and at 4º C (Kurskall-Wallis test and Dunn test, p > 0.05). The reduction percentage was higher when in the absence of organic matter and at 21 ± 2° C (Mann-Whitney test p > 0.05). The modified thin layer cultivation technique was practicable for the realization of the disinfectant tests and allowed an earlier visualization of the colonies (7 days medium). The 2.5% sodium hypochlorite had its mycobactericidal activity diminished when in the presence of organic matter and at the temperature of 4° C.
KEY WORDS
Disinfectants;
Mycobacterium bovis
; tuberculosis; Middlebrook; thin layer
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