Evaluation of the efficacy of bleach routinely used in health facilities against Mycobacterium tuberculosis isolates in Ethiopia
Introduction: In Ethiopia, the most widely used disinfectant is 5% Hypochlorites. However, Ethiopian national health safety and infection prevention guideline recommendation on the use of bleach is not consistent and varying from 0.1%-4%. The purpose of this study was therefore to assess the effective time-concentration relationship of sodium hypochlorite against Mycobacterium tuberculosis complex isolates in the absence of any organic load.
Methods: This experimental study was conducted in Bahir Dar Regional laboratory from February-June 2013. Test suspensions of 1.5 X 108 CFU/ml prepared using normal saline containing 0.5% tween 80. From 5% stock, 0.1%, 0.5%, 1% and 2% bleach was prepared. A 1ml of test strain suspension and 1ml of bleach mixed and allowed to stand until the specified time achieved, neutralized by 48 ml phosphate buffer. 100<l from the diluted sediment were spread on two L-J mediums and incubated at 37°C for 8 weeks.
Results: When 0. 1% bleach was used for 10 min, majority 11/20 of isolates showed 3 x 103 CFU/ml growth (ME=4.4) which was inefficient. However, when the time increased, the log10 reduction was acceptable, ME >5 and it was effective. The bleach solution containing 0.5% and above was effective in all
respective times. In this study, there is no difference observed in the tuberculocidal activity of bleach against resistant and sensitive strains.
Conclusion: Our study showed that in the absence of any organic load, 0.1% bleaches over 15 min and 0.5 % bleaches over 10 min was found to be tuberculocidal.
Key words: Efficacy, Bleach, M. tuberculosis, Ethiopia, organic load