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Journal of Clinical Microbiology, Oct 1996, 2435-2439, Vol 34, No. 10
LE Desjardin, MD Perkins, L Teixeira, MD Cave and KD Eisenach
Reverse transcriptase PCR (RT-PCR) is an important tool for Mycobacterium
tuberculosis research and diagnostics. A standard procedure using
N-acetyl-L-cysteine (NALC) and NaOH has been widely adopted for digestion
and decontamination of sputum specimens for mycobacterial culture. The
objective of this study was to determine the compatibility of this method
with the recovery of RNA for RT-PCR assays. Nineteen sputum specimens were
collected from smear-positive, pretreatment tuberculosis patients. After
homogenization with NALC and glass beads, specimens were further processed
by the addition of either NaOH, as per the standard decontamination
protocol, or phosphate buffer. RNA was prepared by using a modified
guanidine-phenol extraction method developed specifically for sputum
sediments. DNA was isolated from the same specimens. Reverse transcriptions
of alpha antigen (85B protein) mRNA and 16S rRNA were performed together,
and aliquots were removed for separate PCRs. In all specimens, the 85B mRNA
target was greatly diminished by treatment with NaOH; however, the 16S rRNA
target remained unaffected. Storing sputum specimens for 48 h at 4 degrees
C before processing did not seem to affect the integrity or yield of RNA;
however, some degradation occurred by 72 h. Data suggest that the NaOH-NALC
method for processing sputum samples is not suitable for detecting mRNA
targets in RT-PCR assays.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Alkaline decontamination of sputum specimens adversely affects stability of mycobacterial mRNA
Department of Pathology, University of Arkansas for Medical Sciences, Little Rock, USA.
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