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KMID : 1100720140340030203
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Annals of Laboratory Medicine
2014 Volume.34 No. 3 p.203 ~ p.209
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Evaluation of Propidium Monoazide Real-Time PCR for Early Detection of Viable Mycobacterium tuberculosis in Clinical Respiratory Specimens
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Kim Young-Jin
Lee Sun-Min
Park Byung-Kyu
Kim Sung-Soo
Yi Jong-Youn
Kim Hyung-Hoi
Lee Eun-Yup
Chang Chulhun L
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Abstract
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Background: Conventional acid-fast bacilli (AFB) staining cannot differentiate viable from dead cells. Propidium monoazide (PMA) is a photoreactive DNA-binding dye that inhibits PCR amplification by DNA modification. We evaluated whether PMA real-time PCR is suitable for the early detection of viable Mycobacterium tuberculosis (MTB) in clinical respiratory specimens.
Methods: A total of 15 diluted suspensions from 5 clinical MTB isolates were quadruplicated and subjected to PMA treatment and/or heat inactivation. Eighty-three AFB-positive sputum samples were also tested to compare the ΔCT values (CT value in PMA-treated sputum samples?CT value in non-PMA-treated sputum samples) between culture-positive and culture-negative specimens. Real-time PCR was performed using Anyplex MTB/NTM Real-Time Detection (Seegene, Korea), and the CT value changes after PMA treatment were compared between culture-positive and culture-negative groups.
Results: In MTB suspensions, the increase in the CT value after PMA treatment was significant in dead cells (P=0.0001) but not in live cells (P=0.1070). In 14 culture-negative sputum samples, the median ΔCT value was 5.3 (95% confidence interval [CI], 4.1-8.2; P<0.0001), whereas that in 69 culture-positive sputum samples was 1.1 (95% CI, 0.7-2.0). In the ROC curve analysis, the cutoff ΔCT value for maximum sensitivity (89.9%) and specificity (85.7%) for differentiating dead from live cells was 3.4.
Conclusions: PMA real-time PCR is a useful approach for differentiating dead from live bacilli in AFB smear-positive sputum samples.
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KEYWORD
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Mycobacterium tuberculosis, Propidium monoazide, Real-time PCR
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