Abstract
IntroductionIn 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.MethodsThis 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. 100µl from the diluted sediment were spread on two L-J mediums and incubated at 37°C for 8 weeks.ResultsWhen 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.ConclusionOur 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.
Highlights
In Ethiopia, the most widely used disinfectant is 5% Hypochlorites
10 multidrug resistant and 10 sensitive Mycobacterium tuberculosis complex (MTBC) strains were used for assessing the tuberculocidal effect of bleach with specified concentration and exposure time
We found that the pH of bleach decreased as concentration of bleach decreased (Table 2)
Summary
In Ethiopia, the most widely used disinfectant is 5% Hypochlorites. 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 to assess the effective time-concentration relationship of sodium hypochlorite against Mycobacterium tuberculosis complex isolates in the absence of any organic load. Antimicrobial activity can be influenced by many factors such as formulation effects, presence of an organic load, synergy, temperature, dilution, and test method [2,3,4]. The most commonly used chloro products in Ethiopian health care facilities are aqueous solutions of 5% sodium hypochlorite usually called household bleach (Chora Gas and chemical producing Factory, Addis Ababa, Ethiopia). Ethiopian national health safety and infection prevention guideline recommendation on the use of bleach as a disinfectant is not consistent and varying from 0.1%-4% [5,6]
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