Biocidal effect of bleach on Mycobacterium tuberculosis: a safety measure.
BACKGROUND
Although treatment of sputum using bleach has shown increased sensitivity in smear microscopy, the safety aspect of sodium hypochlorite (NaOCl) has not been addressed.


OBJECTIVE
To determine the biocidal effect of NaOCl on Mycobacterium tuberculosis when used as a safety measure in direct sputum smear microscopy for the diagnosis of tuberculosis (TB).


METHODS
A total of 156 smear- and culture-positive pooled sputum specimens were assessed for the viability of M. tuberculosis after treatment with NaOCl. Each specimen was divided into 11 equal portions. One portion was directly cultured. Each of five portions was treated with 3.5% NaOCl and the other five with 5% NaOCl. Specimens were then cultured at intervals of 15 min and 1, 3, 15 and 24 h.


RESULTS
A total of 18 (11.5%) specimens showed growth after treatment with NaOCl. Of these, 5 (3.2%) showed growth upon treatment with 3.5% NaOCl at 15 min and 15 and 24 h. Ten (6.4%) showed growth after treatment with 5% NaOCl between 15 min and 3 h, but none showed growth after 15 h. Three (1.9%) specimens showed growth in both concentrations.


CONCLUSIONS
Our preliminary findings show that exposure of sputum to 5% NaOCl for at least 15 h may be a safety procedure in smear microscopy for the diagnosis of TB. However, further studies are warranted.
Githui
W A
WA
Centre for Respiratory Diseases Research (CRDR), Kenya Medical Research Institute (KEMRI), P O Box 47855-00100 GPO, Nairobi, Kenya. wgithui@hotmail.com
Matu
S W
SW
Tunge
N
N
Juma
E
E
D001431:Bacteriological Techniques; D017077:Culture Media, Conditioned; D006801:Humans; D008853:Microscopy / Q000379:methods; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000254:growth & development* / Q000302:isolation & purification*; D012449:Safety; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D012973:Sodium Hypochlorite / Q000378:metabolism / Q000494:pharmacology*; D013183:Sputum / Q000382:microbiology*; D014376:Tuberculosis / Q000175:diagnosis
D017077:Culture Media, Conditioned; D012973:Sodium Hypochlorite