Direct Detection by the Xpert MTB/RIF Assay and Characterization of Multi and Poly Drug-Resistant Tuberculosis in Guinea-Bissau, West Africa

PLoS One. 2015 May 27;10(5):e0127536. doi: 10.1371/journal.pone.0127536. eCollection 2015.


Background: This study aimed to evaluate the usefulness of the Xpert MTB/RIF assay for the rapid direct detection of M. tuberculosis complex (MTBC) strains and rifampicin resistance associated mutations in a resource-limited setting such as Guinea-Bissau and its implications in the management of tuberculosis (TB) and drug resistant tuberculosis, complementing the scarce information on resistance and genotypic diversity of MTBC strains in this West African country.

Methods and results: This cross-sectional prospective study included 100 consecutive TB patients with positive acid-fast smears at two months of anti-tuberculosis treatment or in a re-treatment situation, between May and December 2012. Resistance to rifampicin was detected using the GeneXpert system and the Xpert MTB/RIF assay. MTBC isolates obtained with the BACTEC MGIT 960 system were tested for susceptibility to first- and second-line anti-tuberculosis drugs. Overall, the prevalence of multidrug-resistant tuberculosis (MDR-TB) was found to be 9 cases. Of these, 67% (6 patients) of confirmed MDR-TB cases had no past history of TB treatment and 33% (3 patients) were previously treated cases. Extensively drug-resistant TB was not found. Molecular typing of the MDR-TB strains revealed recent transmission patterns of imported MDR strains.

Conclusions: The Xpert MTB/RIF assay was reliable for the detection of rifampicin resistant MTBC strains directly from sputum samples of patients undergoing first-line treatment for two months, being more trustworthy than the simple presence of acid-fast bacilli in the smear. Its implementation is technically simple, does not require specialized laboratory infrastructures and is suitable for resource-limited settings when a regular source of electricity and maintenance is available as well as financial and operation sustainability is guaranteed by the health authorities. A high prevalence of MDR-TB among patients at risk of MDR-TB after two months of first-line treatment was found, in support of the WHO recommendations for its use in the management of this risk group.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antitubercular Agents / pharmacology*
  • Antitubercular Agents / therapeutic use
  • Cross-Sectional Studies
  • Female
  • Genotype
  • Guinea-Bissau / epidemiology
  • Humans
  • Male
  • Molecular Typing
  • Mutation
  • Mycobacterium tuberculosis / drug effects
  • Mycobacterium tuberculosis / genetics
  • Mycobacterium tuberculosis / isolation & purification*
  • Mycobacterium tuberculosis / physiology
  • Patient Selection
  • Rifampin / pharmacology*
  • Rifampin / therapeutic use
  • Risk
  • Time Factors
  • Tuberculosis, Multidrug-Resistant / drug therapy
  • Tuberculosis, Multidrug-Resistant / epidemiology
  • Tuberculosis, Multidrug-Resistant / microbiology*


  • Antitubercular Agents
  • Rifampin

Grants and funding

The Pos-Doc study project of Paulo Rabna was funded by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through a grant of the Global Program for Science of UNESCO (SFRH/BPD/5148/2011). Gulbenkian Foundation is acknowledged for a clinical research grant to Gema Ponce. Diana Machado was supported by grant SFRH/BD/65060/2009 from FCT, Portugal. João Perdigão was supported by post-doctoral fellowships from Project PTDC/SAU-EPI/122400/2010 and SFRH/BPD/95406/2013 from FCT, Portugal. The funding Institutions had no role in study design, data collection, analysis, interpretation, preparation of the manuscript, or decision to publish.