Effectiveness of Nalc (N-Acetyl-L-Cysteine) to Improve Microscopic Examination of Acid Fast Bacilli: A Comparative Study of NaOH-NALC and Sulfuric Acid Decontamination in Detecting Mycobacteria

Abstract

We compared the NaOH-N-acetylcysteine (NaOH-NALC) and the sulfuric acid decontamination procedure in thedetection of mycobacteria using the Mycobacteria Growth Indicator Tube (MGIT).In total 219 sputum specimens were collected from 142 Zambian patients andsubjected to mycobacterial culture. One half of the specimen was decontaminatedwith NaOH-NALC and the other half was decontaminated with sulfuric acid. Fromthe 438 samples a total of 261 (60%) cultures yielded growth of mycobacteria,consisting of 22 different species. The sulfuric acid method was moresuccessful than the NaOH-NALC method in recovering mycobacteria in MGITs (146versus 115 respectively, p=0.001).Of the 146 positive mycobacterial cultures recovered after sulfuric aciddecontamination 28 were Mycobacterium tuberculosis, 84 nontuberculousmycobacteria (NTM) and 34 acid fast bacterial isolates which could not beidentified to the species level. The 115 mycobacteria recovered by theNaOH-NALC method consisted of 34 M.tuberculosis strains, 55 NTM and 26 acid fast bacteria that could not beidentified.