I would like to know which is the easiest and cheapest but at the same time sensitive and specific method.
The n-acetyl-L-cysteine (NALC)- sodium hydroxide (NaOH) method is the best all-rounder, probably. For sputum of cystic fibrosis patients, you can supplement it with oxalic acid treatment or chlorhexidine. See the excellent papers by Whittier S, et al. in J Clin Microbiol in 1993 and 1996 and the Ferroni A et al paper in J Clin Microbiol 2006. If you are keen to isolate nontuberculous mycobacteria, the 3% sulfuric acid may be better than NALC-NaOH, see Buijtels P, et al., J Microbiol Methods 2006.
Yes. The NALC-NAOH method is best. You can see a paper by Mukesh Sharma "Comparison of modified Petroff's and N-acetyl-L-cysteine-sodium hydroxide methods for sputum decontamination in tertiary care hospital in India" and WHO guideline too.
Yes, the Sodium hypochlorite which is also sold in the market as "bleach" is perfect.
Dear Philipp
In Laos, we tested the use of the bleach method as a safe and easy tools.
Int J Tuberc Lung Dis. 2009 Sep;13(9):1124-9.
The bleach method improves the detection of pulmonary tuberculosis in Laos.
Ongkhammy S, Amstutz V, Barennes H, Buisson Y.
Source
Institut de la Francophonie pour la Médecine tropicale, Vientiane, Lao Peoples' Democratic Republic.
Abstract
SETTING:
Laos has a high prevalence of tuberculosis (TB) and a low prevalence of human immunodeficiency virus/acquired immune-deficiency syndrome (HIV/AIDS). Mycobacterium tuberculosis culture is not yet available. Case finding is based on the microscopic detection of acid-fast bacilli (AFB) in sputum. Liquefaction and concentration using sodium hypochlorite (bleach) could improve its yield.
OBJECTIVE:
To assess the gain due to the bleach method and its feasibility in Laos, and to compare the classical method sputum processing (direct microscopy) and the bleach method for AFB detection over 3 consecutive months at a central site (Vientiane) and for 1 month at a peripheral site (Attapeu).
RESULTS:
Of 1675 sputum samples collected from 612 patients, respectively 206 (12.3%) and 275 (16.4%) were AFB-positive by the direct and bleach methods (P = 0.0007), i.e., an increase in smear positivity rate of 33.5% (95%CI 31.2-35.8). The superiority of the bleach method was confirmed, regardless of the site, the aspect of the sputum and delay before analysis. This method yielded 24 more TB patients.
CONCLUSION:
The bleach method, which is very easy to use, could significantly increase the yield of sputum smear microscopy for the detection of pulmonary TB in Laos.
Dears, thanks for all the information, very usefull indeed.
Dear Mr Barennes
The bleach method looks very atractive indeed. Did you measure, or do you have any information about if it has any impact on the rates of culture positivity?
The NALC-NAOH method is best. Throughout my research I have used this method and the results obtained were excellent.
Hello colleagues,
Thanks much for your valuable answers. I have a question about bleach method: Do you recommend bleach method for sputum liquefaction, prior to DNA extraction of M.Tuberculosis? considering that PCR will be subsequently performed...
In another word, Does bleach inhibit PCR?
Thanks much!.
Best method is to use NaoH along with N-acetyl L-cystine which is not only bacteruicidal and also provide mucolytic activty
Hi, could you replied your question "Which is the best method for decontamination of a sputum sample before culturing it for Mycobacterium tuberculosis"?
So far NaOH NALC method is the best. 0.7% Chlorhexidine would have been the best if it work with the MGIT system.
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