Direct detection of rpoB and katG gene mutations of Mycobacterium tuberculosis in clinical samples

Seven hundred thirty-seven clinical samples from 460 patients were processed for direct detection of Mycobacterium tuberculosis complex by a semiautomated ligase chain reaction commercial assay, the LCx Mycobacterium tuberculosis Assay (LCx assay) from Abbott Laboratories. Results were compared to those of direct microscopy and standard microbiological culture. Of 26 patients (5.7%) with a culture positive for M. tuberculosis, 22 (84.6%) were found positive by the LCx assay. The sensitivity of the LCx assay was 98% for smear-positive samples and 27% for smear-negative samples. With an overall culture positivity rate forM. tuberculosis of 8.3% (61 of 737 samples) and after resolution of discrepant results according to clinical data, the sensitivity, specificity, and positive and negative predictive values of the LCx assay were 78, 100, 95, and 98%, respectively, compared to 85, 100, 100, and 98%, respectively, for culture and 67, 99, 87, and 97%, respectively, for acid-fast staining. In conclusion, the LCx assay proved satisfactory and appears to be an easy-to-use 1-day test which must be used with standard culture methods but can considerably reduce diagnosis time versus culture. However, its clinical interest appears to be limited in our population with low mycobacterial prevalence because of its cost considering the small gain in sensitivity versus direct microscopy.

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Evaluation of the BD ProbeTec ET system for the direct detection of Mycobacterium tuberculosis from clinical samples

British Journal of Biomedical Science ◽

10.1080/09674845.2008.11732787 ◽

2008 ◽

Vol 65 (1) ◽

pp. 7-12 ◽

Cited By ~ 8

Author(s):

P. Barber

Keyword(s):

Mycobacterium Tuberculosis ◽

Direct Detection ◽

Clinical Samples

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Rolling Circle Amplification for Direct Detection of rpoB Gene Mutations in Mycobacterium tuberculosis Isolates from Clinical Specimens

Journal of Clinical Microbiology ◽

10.1128/jcm.00065-14 ◽

2014 ◽

Vol 52 (5) ◽

pp. 1540-1548 ◽

Cited By ~ 13

Author(s):

X. Chen ◽

B. Wang ◽

W. Yang ◽

F. Kong ◽

C. Li ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Direct Detection ◽

Rolling Circle Amplification ◽

Gene Mutations ◽

Rpob Gene ◽

Rolling Circle ◽

Clinical Specimens

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Direct Detection of Mycobacterium tuberculosis Complex in Clinical Samples by a Molecular Method Based on GenoQuick Technology

Journal of Clinical Microbiology ◽

10.1128/jcm.00567-12 ◽

2012 ◽

Vol 50 (6) ◽

pp. 2089-2091 ◽

Cited By ~ 7

Author(s):

Raquel Moure ◽

Miriam Torres ◽

Rogelio Martín ◽

Fernando Alcaide

Keyword(s):

Mycobacterium Tuberculosis ◽

Mycobacterium Tuberculosis Complex ◽

Direct Detection ◽

Clinical Samples ◽

Tuberculosis Complex ◽

Molecular Method

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Evaluation of the GenoType Mycobacteria Direct assay for direct detection of the Mycobacterium tuberculosis complex obtained from sputum samples

Journal of Medical Microbiology ◽

10.1099/jmm.0.013490-0 ◽

2010 ◽

Vol 59 (8) ◽

pp. 930-934 ◽

Cited By ~ 11

Author(s):

Nuri Kiraz ◽

Imran Saglik ◽

Abdurrahman Kiremitci ◽

Nilgun Kasifoglu ◽

Yurdanur Akgun

Keyword(s):

Mycobacterium Tuberculosis ◽

Sensitivity And Specificity ◽

Direct Detection ◽

Clinical Findings ◽

23S Rrna ◽

Clinical Samples ◽

Culture Methods ◽

Carbol Fuchsin ◽

Lowenstein Jensen ◽

The Difference

An increase in the prevalence of tuberculosis (TB) in recent years has accelerated the search for novel tools for the rapid diagnosis of TB infection. This study evaluated the GenoType Mycobacteria Direct (GTMD) assay (Hain Lifescience) for direct detection of the Mycobacterium tuberculosis complex (MTBC) from sputum samples and compared it with conventional methods. The GTMD test is a commercial assay produced using strip techniques and works based on a nucleic acid sequence-based amplification technique. This test allows 23S rRNA amplification-based detection of MTBC, Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium kansasii and Mycobacterium malmoense directly from decontaminated clinical samples within 6 h. In the present study, 115 sputum samples were processed to detect acid-fast bacilli (AFB) using two microscopy methods (carbol fuchsin and fluorescent staining), two culture methods [Löwenstein–Jensen (LJ) and BACTEC 12B media] and the GTMD test. The results showed that 86 of the samples were positive by direct microscopy, 84 were positive by BACTEC 12B culture, 73 were positive by LJ culture and 95 were positive by the GTMD test. All of the isolates turned out to be MTBC. Moreover, the sensitivity and specificity of the GTMD test for MTBC in patients were 97 and 58 %, respectively, taking the culture combination as the gold standard. When the test was compared with culture of samples from anti-TB-treated patients, the sensitivity and specificity for the test were 100 and 15 %, respectively. Low specificity in treated people might arise from depressed proliferation of AFB. As the two methods target the same living bacilli, the difference is obviously notable. When the culture results and clinical findings of the patients were evaluated together (true-positive specimens), the sensitivity and specificity values of the GTMD test for all patients were 97 and 90 %, respectively. However, both of these values increased to 100 % for the patients receiving anti-TB treatment. These results implied that, to determine whether the patient's sputum contains living AFB, more sensitive techniques should be employed during the follow-up of the patients. These observations suggest that the GTMD method can be useful for early diagnosis of clinically and radiologically suspicious TB cases where smears are negative for Mycobacterium. In addition, the use of a GTMD test in smear-positive cases is helpful and practical in order to identify MTBC quickly. This allows more rapid treatment decisions and infection control precautions.

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