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Open Access Research article

Sequence analysis for detection of drug resistance in Mycobacterium tuberculosis complex isolates from the Central Region of Cameroon

Emmanuel Mouafo Tekwu156, Larissa Kamgue Sidze156, Jean-Paul Assam Assam16, Jean-Claude Tedom16, Serges Tchatchouang16, Gaëlle Guiewi Makafe16, Anne-Laure Tchokote Wetewale16, Christopher Kuaban2, Sara Eyangoh3, Francine Ntoumi456, Véronique N Penlap Beng16* and Matthias Frank567*

Author Affiliations

1 Laboratory for Tuberculosis Research (LTR), Biotechnology Centre (BTC)-Nkolbison, University of Yaoundé I, Yaoundé, Cameroon

2 Pneumology unit, Jamot Hospital, Yaoundé, Cameroon

3 Mycobacteriology Service, Reference laboratory of NTP, Centre Pasteur of Cameroon-Pasteur Institute International Network, Yaoundé, Cameroon

4 Fondation Congolaise pour la Recherche Médicale, Université Marien Gouabi, Brazzaville, Congo

5 Institute for Tropical Medicine, University of Tübingen, Tübingen, Germany

6 Central African Network for Tuberculosis, AIDS/HIV and Malaria (CANTAM), Brazzaville, Congo

7 Deutsches Zentrum für Infektionsforschung (DZIF), Tübingen, Germany

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BMC Microbiology 2014, 14:113  doi:10.1186/1471-2180-14-113

Published: 3 May 2014

Abstract

Background

The potential of genetic testing to rapidly diagnose drug resistance has lead to the development of new diagnostic assays. However, prior to implementation in a given setting, the association of specific mutations with specific drug resistance phenotypes should be evaluated. The purpose of this study was to evaluate molecular markers in predicting drug resistance in the Central Region of Cameroon.

Results

From April 2010 and March 2011, 725 smear positive pulmonary tuberculosis patients were enrolled and all positive cultures were tested for drug susceptibility. A total of 63 drug resistant and 100 drug sensitive Mycobacterium tuberculosis complex clinical isolates were screened for genetic mutations in katG, inhA, ahpC, rpoB, rpsL, rrs, gidB and embCAB loci using DNA sequencing. Of the 44 isoniazid resistant (INHR) isolates (24 high level, 1 μg/ml and 20 low level, 0.2 μg/ml), 73% (32/44) carried the katG315 and/or the -15 inhA promoter mutations. Of the 24 high level INHR, 17 (70.8%) harbored katG315 mutation, 1 a point mutation (-15C → T) in the inhA promoter and 6 were (25.0%) wild types. Thus, for INHR high level detection, katG315 mutation had a specificity and a sensitivity of 100% and 70.8% respectively. Of the 20 low level INHR, 10 (50.0%) had a -15C → T mutation in the inhA promoter region, and 1 (2.2%) a -32G → A mutation in the ahpC promoter region. All of the 7 rifampicin resistant (RIFR) isolates carried mutations in the rpoB gene (at codons Ser531Leu (71.4%), His526Asp (14.3%), and Asp516Val (14.3%)). Of the 27 streptomycin resistant (SMR) isolates, 7 carried mutations at the rpsL and the gidB genes. 1 of the 2 ethambutol resistant (EMBR) isolates displayed a mutation in embB gene.

Conclusion

This study provided the first molecular investigation assessing the correlation of phenotypic to genotypic characteristics on MTB isolates from the Central Region of Cameroon using DNA sequencing. Mutations on rpoB, katG315 and -15 point mutations in inhA promoter loci could be used as markers for RIF and INH -resistance detection respectively.

Keywords:
Phenotype; Mutation; Drug resistance; Mycobacterium tuberculosis; Cameroon