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A novel sample processing method for rapid detection of tuberculosis in the stool of pediatric patients using the Xpert MTB/RIF assay

Banada, PP and Naidoo, U and Deshpande, S and Karim, F and Flynn, JL and O'Malley, M and Jones, M and Nanassy, O and Jeena, P and Alland, D (2016) A novel sample processing method for rapid detection of tuberculosis in the stool of pediatric patients using the Xpert MTB/RIF assay. PLoS ONE, 11 (3).

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© 2016 Banada et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background: Tuberculosis (TB) is difficult to diagnose in children using molecular tests, because children have difficulty providing respiratory samples. Stool could replace sputum for diagnostic TB testing if adequate sample processing techniques were available. Methods We developed a rapid method to process large volumes of stool for downstream testing by the Xpert MTB/RIF (Xpert) TB-detection assay. The method was tested and optimized on stool samples spiked with known numbers of M. tuberculosis colony forming units (CFU), and stools from M. tuberculosis-infected cynomolgus macaques (Macaca fascicularis). Performance was scored on number of positive Xpert tests, the cycle thresholds (Cts) of the Xpert sample-processing control (SPC), and the Cts of the M. tuberculosis-specific rpoB probes. The method was then validated on 20 confirmed TB cases and 20 controls in Durban, South Africa. Results: The assay's analytical limit of detection was 1,000 CFU/g of stool. As much as one gram of spiked stool could be tested without showing increased PCR inhibition. In analytical spiking experiments using human stool, 1 g samples provided the best sensitivity compared to smaller amounts of sample. However, in Macaques with TB, 0.6g stool samples performed better than either 0.2g or 1.2g samples. Testing the stool of pediatric TB suspects and controls suggested an assay sensitivity of 85% (95% CI 0.6-0.9) and 84% (95% CI 0.6-0.96) for 0.6g and 1.2g stool samples, respectively, and a specificity of 100% (95% CI 0.77-1) and 94% (95% CI 0.7-0.99), respectively. Conclusion: This novel approach may permit simple and rapid detection of TB using pediatric stool samples.


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Item Type: Article
Status: Published
CreatorsEmailPitt UsernameORCID
Banada, PP
Naidoo, U
Deshpande, S
Karim, F
Flynn, JLjoanne@pitt.eduJOANNE
O'Malley, M
Jones, M
Nanassy, O
Jeena, P
Alland, D
ContributionContributors NameEmailPitt UsernameORCID
Date: 1 March 2016
Date Type: Publication
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Journal or Publication Title: PLoS ONE
Volume: 11
Number: 3
DOI or Unique Handle: 10.1371/journal.pone.0151980
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Microbiology and Molecular Genetics
Refereed: Yes
Date Deposited: 25 Aug 2016 15:57
Last Modified: 04 Feb 2019 15:56


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