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Author Notes:

Correspondence: meredith.holtz@gmail.com; mreimer2@tulane.edu

Meredith H. Lora and Melissa J. Reimer-McAtee contributed equally to this work.

Authors’ contributions: Conception of the study- MHL, RHG, DL, FT; Implementation of the study- MHL, MRM, RC, DL, FT; Construction of the manuscript- MRM and MHL; Processing of samples- MHL, MRM, RS, RCh, ME, MV, MS; Data analysis- MP, CB; Editing of manuscript- MHL, MRM, CB, RHG.

All authors read and approved the final manuscript.

We would like to thank the late Luz Caviedes for training the laboratory technicians in Cochabamba, Bolivia, and for being such an available and gracious resource to everyone involved in the project.

We would like to thank Dr. Amilcar Apaza, Dra. Anna Volz Galvez, and Dra Mireya Claros at the TB program in Cochabamba for allowing the study to take place; Casta Pahuasi at La Escuela Técnica de Salud for her help processing the samples in the lab; and J.B. Phu and D. Sara for their technical support.

The authors declare that they have no competing interests.

Funders took no part in the design or interpretation of the study.

The content of this study is solely the responsibility of the authors and does not necessarily represent the views of the funding sources.


Research Funding:

This study was supported by the following grants through the National Institutes of Health: T35-AI065386-04 and T35-AI065385-05.


  • Science & Technology
  • Life Sciences & Biomedicine
  • Infectious Diseases
  • Tuberculosis
  • HIV
  • AIDS
  • MODS
  • Bolivia
  • Resource-scarce
  • String test
  • TB

Evaluation of Microscopic Observation Drug Susceptibility (MODS) and the string test for rapid diagnosis of pulmonary tuberculosis in HIV/AIDS patients in Bolivia

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Journal Title:

BMC Infectious Diseases


Volume 15


, Pages 222-222

Type of Work:

Article | Final Publisher PDF


Background: Tuberculosis (TB) is the most common opportunistic infection and the leading cause of death in HIV-positive people worldwide. Diagnosing TB is difficult, and is more challenging in resource-scarce settings where culture-based diagnostic methods rely on poorly sensitive smear microscopy by Ziehl-Neelsen stain (ZN). Methods: We performed a cross-sectional study examining the diagnostic utility of Microscopic Observation Drug Susceptibility liquid culture (MODS) versus traditional Ziehl-Neelsen staining (ZN) and Lowenstein Jensen culture (LJ) of pulmonary tuberculosis (TB) and multidrug-resistant tuberculosis (MDRTB) in HIV-infected patients in Bolivia. For sputum scarce individuals we assessed the value of the string test and induced sputum for TB diagnosis. The presence of Mycobacterium tuberculosis (Mtb) in the sputum of 107 HIV-positive patients was evaluated by ZN, LJ, and MODS. Gastric secretion samples obtained by the string test were evaluated by MODS in 102 patients. Results: The TB-HIV co-infection rate of HIV patients with respiratory symptoms by sputum sample was 45 % (48/107); 46/48 (96 %) were positive by MODS, 38/48 (79 %) by LJ, and 30/48 (63 %) by ZN. The rate of MDRTB was 9 % (4/48). Median time to positive culture was 10 days by MODS versus 34 days by LJ (p < 0.0001). In smear-negative patients, MODS detected TB in 17/18 patients, compared to 11/18 by LJ (94.4 % vs 61.0 %, p = 0.03 %). In patients unable to produce a sputum sample without induction, the string test cultured by MODS yielded Mtb in of 9/11 (82 %) TB positive patients compared to 11/11 (100 %) with induced sputum. Of the 10 patients unable to produce a sputum sample, 4 were TB-positive by string test. Conclusion: MODS was faster and had a higher Mtb detection yield compared to LJ, with a greater difference in yield between the two in smear-negative patients. The string test is a valuable diagnostic technique for HIV sputum-scarce or sputum-absent patients, and should be considered as an alternative test to induced sputum to obtain sample for Mtb in resource-limited settings. Nine percent of our TB+ patients had MDRTB, which reinforces the need for rapid detection with direct drug susceptibility testing in HIV patients in Bolivia.

Copyright information:

© 2015 Lora et al.

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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