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

Meredith H. Lora¹^*^†, Melissa J. Reimer-McAtee²^*^†, Robert H. Gilman³, Daniel Lozano⁴,Ruth Saravia⁵, Monica Pajuelo⁶, Caryn Bern⁷, Rosario Castro⁴, Magaly Espinoza⁸, Maya Vallejo⁸, Marco Solano⁴, Roxana Challapa⁵ and Faustino Torrico⁴

*Corresponding authors: Meredith H Lora meredith.holtz@gmail.com - Melissa J Reimer-McAtee mreimer2@tulane.edu
† Equal contributors

Author Affiliations

¹Department of Medicine, University of California in San Francisco, 505 Parnassus Ave, Rm 987, San Francisco 94143-0119, CA, USA

²Department of Medicine, Tulane University School of Medicine, New Orleans, LA, USA

³Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA

⁴Facultad de Medicina, Universidad Mayor de San Simón, Cochabamba, Bolivia

⁵Colectivo de Estudios Aplicados y Desarrollo Salud y Medio Ambiente, Cochabamba, Bolivia

⁶Universidad Peruana Cayetano Heredia, Lima, Peru

⁷University of California in San Francisco, San Francisco, USA

⁸La Escuela Técnica de Salud, Cochabamba, Bolivia

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BMC Infectious Diseases 2015, 15:222 doi:10.1186/s12879-015-0966-0

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

The electronic version of this article is the complete one and can be found online at:http://www.biomedcentral.com/1471-2334/15/222

Received:	3 February 2015
Accepted:	28 May 2015
Published:	6 June 2015

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Abstract

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.