scholarly journals Mixed Mycobacterium tuberculosis Complex Infections and False-Negative Results for Rifampin Resistance by GeneXpert MTB/RIF Are Associated with Poor Clinical Outcomes

2014 ◽  
Vol 52 (7) ◽  
pp. 2422-2429 ◽  
Author(s):  
N. M. Zetola ◽  
S. S. Shin ◽  
K. A. Tumedi ◽  
K. Moeti ◽  
R. Ncube ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Clinical Outcomes ◽  
Mycobacterium Tuberculosis Complex ◽  
False Negative ◽  
Tuberculosis Complex ◽  
Negative Results ◽  
False Negative Results ◽  
Rifampin Resistance

scholarly journals Mycobacterium tuberculosis complex detected by modified fluorescent in situ hybridization in lymph nodes of clinical samples

2011 ◽  
Vol 6 (01) ◽  
pp. 58-66 ◽  
Author(s):  
Juan Rodriguez-Nuñez ◽  
Francisco J Avelar ◽  
Francisco Marquez ◽  
Bruno Rivas-Santiago ◽  
Cesar Quiñones ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Lymph Node ◽  
Mycobacterium Tuberculosis Complex ◽  
Extrapulmonary Tuberculosis ◽  
Clinical Samples ◽  
Tuberculosis Complex ◽  
Tissue Samples ◽  
Negative Results ◽  
Modified Dna ◽  
Pna Fish

Introduction:  Lymph node tuberculosis (TB) is the leading cause of extrapulmonary tuberculosis and is the most frequently identified type in Aguascalientes, Mexico. Conventional diagnosis has serious limitations for rapid detection of extrapulmonary tuberculosis in clinical samples. Here PCR and modified FISH have been tested as complementary diagnosis methods for extrapulmonary tuberculosis. Methodology: The specific insertion sequence IS6110 for Mycobacterium tuberculosis complex was used to perform PCR and build DNA and PNA FISH probes (20bp). PCR and modified DNA and PNA FISH assays were performed to evaluate 41 lymph node paraffin-embedded tissue samples, in comparison with the histopathology diagnosis, which was considered the gold standard (22 positive and 19 negative). Results: In comparison with histopathology diagnosis PCR showed 62.5 % sensitivity and 77.8 % specificity (χ2 = 4.583 p < 0.05). Modified DNA FISH showed 71.4% sensitivity and 84.6% specificity (χ2 = 11.21 p < 0.05). PNA FISH showed 66.7% sensitivity and 60.0% specificity (χ2 = 2.93 p > 0.05). Ziehl Neelsen stain was positive in only four cases of 22 lymph node samples positive to histopathology.  In contrast, PCR and modified DNA FISH were positive in 20 cases of the same group. The negative cases were coincident in all tests.Conclusions: PCR and DNA FISH showed a significant increase in the number of cases detected and also showed higher sensitivity and specificity compared with data reported by traditional methodology. In developing countries, these techniques could help to complement the early diagnosis and timely treatment of extrapulmonary tuberculosis.

scholarly journals A unique strain of Mycobacterium tuberculosis and a cautionary tale for users of molecular techniques

2004 ◽  
Vol 25 (4) ◽  
pp. 32
Author(s):  
C Frank Haverkort ◽  
Christopher Gilpin
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Binding Sites ◽  
Direct Detection ◽  
False Negative ◽  
Molecular Techniques ◽  
Cautionary Tale ◽  
Testing Methods ◽  
Negative Results ◽  
False Negative Results ◽  
Unique Strain

Molecular techniques are now widely applied in Australia and elsewhere for the direct detection of Mycobacterium tuberculosis DNA in clinical specimens and culturally enhanced material. All nucleic acid testing methods have the potential to give false negative results due to mutations that may arise at primer or probe binding sites. We describe one such strain of M. tuberculosis that was encountered in 1995 and that has not been encountered in Australia since.

scholarly journals Distribution of a Specific 500-Base-Pair Fragment in Mycobacterium bovis Isolates from Sardinian Cattle

2000 ◽  
Vol 38 (10) ◽  
pp. 3837-3839 ◽  
Author(s):  
Leonardo A. Sechi ◽  
Ilaria Duprè ◽  
Guido Leori ◽  
Giovanni Fadda ◽  
Stefania Zanetti
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Mycobacterium Bovis ◽  
Base Pair ◽  
False Negative ◽  
Negative Results ◽  
False Negative Results ◽  
Base Pair Fragment ◽  
Pair Fragment

Amplification of a specific, 500-bp fragment fromMycobacterium bovis isolates and use of the fragment to differentiate between Mycobacterium tuberculosis andM. bovis was previously reported (J. G. Rodriguez, G. A. Meja, P. Del Portillo, M. E. Patarroyo, and L. A. Murillo, Microbiology 141:2131–2138, 1995). In the present study, 30M. bovis isolates from Sardinian cattle were examined for the presence of this 500-bp fragment; 4 of the 30 isolates lacked the fragment. This result indicates that identification of M. bovis strains by amplification of the 500-bp sequence may lead to false-negative results.

scholarly journals The New Xpert MTB/RIF Ultra: Improving Detection of Mycobacterium tuberculosis and Resistance to Rifampin in an Assay Suitable for Point-of-Care Testing

mBio ◽  
2017 ◽  
Vol 8 (4) ◽  
Author(s):  
Soumitesh Chakravorty ◽  
Ann Marie Simmons ◽  
Mazhgan Rowneki ◽  
Heta Parmar ◽  
Yuan Cao ◽  
...  
Keyword(s):  
False Positive ◽  
Point Of Care ◽  
False Negative ◽  
World Health ◽  
Negative Results ◽  
Operational Characteristics ◽  
False Negative Results ◽  
Smear Negative ◽  
Rifampin Resistance ◽  
Health Organization

ABSTRACT The Xpert MTB/RIF assay (Xpert) is a rapid test for tuberculosis (TB) and rifampin resistance (RIF-R) suitable for point-of-care testing. However, it has decreased sensitivity in smear-negative sputum, and false identification of RIF-R occasionally occurs. We developed the Xpert MTB/RIF Ultra assay (Ultra) to improve performance. Ultra and Xpert limits of detection (LOD), dynamic ranges, and RIF-R rpoB mutation detection were tested on Mycobacterium tuberculosis DNA or sputum samples spiked with known numbers of M. tuberculosis H37Rv or Mycobacterium bovis BCG CFU. Frozen and prospectively collected clinical samples from patients suspected of having TB, with and without culture-confirmed TB, were also tested. For M. tuberculosis H37Rv, the LOD was 15.6 CFU/ml of sputum for Ultra versus 112.6 CFU/ml of sputum for Xpert, and for M. bovis BCG, it was 143.4 CFU/ml of sputum for Ultra versus 344 CFU/ml of sputum for Xpert. Ultra resulted in no false-positive RIF-R specimens, while Xpert resulted in two false-positive RIF-R specimens. All RIF-R-associated M. tuberculosis rpoB mutations tested were identified by Ultra. Testing on clinical sputum samples, Ultra versus Xpert, resulted in an overall sensitivity of 87.5% (95% confidence interval [CI], 82.1, 91.7) versus 81.0% (95% CI, 74.9, 86.2) and a sensitivity on sputum smear-negative samples of 78.9% (95% CI, 70.0, 86.1) versus 66.1% (95% CI, 56.4, 74.9). Both tests had a specificity of 98.7% (95% CI, 93.0, 100), and both had comparable accuracies for detection of RIF-R in these samples. Ultra should significantly improve TB detection, especially in patients with paucibacillary disease, and may provide more-reliable RIF-R detection. IMPORTANCE The Xpert MTB/RIF assay (Xpert), the first point-of-care assay for tuberculosis (TB), was endorsed by the World Health Organization in December 2010. Since then, 23 million Xpert tests have been procured in 130 countries. Although Xpert showed high overall sensitivity and specificity with pulmonary samples, its sensitivity has been lower with smear-negative pulmonary samples and extrapulmonary samples. In addition, the prediction of rifampin resistance (RIF-R) in paucibacillary samples and for a few rpoB mutations has resulted in both false-positive and false-negative results. The present study is the first demonstration of the design features and operational characteristics of an improved Xpert Ultra assay. This study also shows that the Ultra format overcomes many of the known shortcomings of Xpert. The new assay should significantly improve TB detection, especially in patients with paucibacillary disease, and provide more-reliable detection of RIF-R. IMPORTANCE The Xpert MTB/RIF assay (Xpert), the first point-of-care assay for tuberculosis (TB), was endorsed by the World Health Organization in December 2010. Since then, 23 million Xpert tests have been procured in 130 countries. Although Xpert showed high overall sensitivity and specificity with pulmonary samples, its sensitivity has been lower with smear-negative pulmonary samples and extrapulmonary samples. In addition, the prediction of rifampin resistance (RIF-R) in paucibacillary samples and for a few rpoB mutations has resulted in both false-positive and false-negative results. The present study is the first demonstration of the design features and operational characteristics of an improved Xpert Ultra assay. This study also shows that the Ultra format overcomes many of the known shortcomings of Xpert. The new assay should significantly improve TB detection, especially in patients with paucibacillary disease, and provide more-reliable detection of RIF-R.

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