Genetic diversity, transmission dynamics and drug resistance of Mycobacterium tuberculosis in Angola

Carla Silva,Diana Machado,Pedro Masakidi,Sofia Clemente,Isabel Couto,Jorge Ramos,João Perdigão,Nuno Taveira,Miguel Viveiros,Isabel Portugal

doi:10.1038/srep42814

Abstract

Tuberculosis (TB) poses a serious public health problem in Angola. No surveillance data on drug resistance is available and nothing is known regarding the genetic diversity and population structure of circulating Mycobacterium tuberculosis strains. Here, we have genotyped and evaluated drug susceptibility of 89 Mycobacterium tuberculosis clinical isolates from Luanda. Thirty-three different spoligotype profiles corresponding to 24 different Shared International Types (SIT) and 9 orphan profiles were detected. SIT 20 (LAM1) was the most prevalent (n = 16, 18.2%) followed by SIT 42 (LAM9; n = 15, 17.1%). Overall, the M. tuberculosis population structure in this sample was dominated by LAM (64.8%) and T (33.0%) strains. Twenty-four-loci MIRU-VNTR analysis revealed that a total of 13 isolates were grouped in 5 distinct clusters. Drug susceptibility data showed that 22 (24.7%) of the 89 clinical isolates were resistant to one or more antibacillary drugs of which 4 (4.5%) were multidrug resistant. In conclusion, this study demonstrates a high predominance of LAM strains circulating in the Luanda setting and the presence of recent transmission events. The rate and the emergence dynamics of drug resistant TB found in this sample are significant and highlight the need of further studies specifically focused on MDR-TB transmission.

Highlights

Despite the importance that the African region plays in a global TB epidemiological context, many countries still lack data on the prevalence of specific M. tuberculosis strains and drug resistance[1]
In the present study we made the first characterization of the genetic diversity and drug resistance of M. tuberculosis complex strains circulating in Luanda, Angola’s most important setting concerning TB epidemiology[2]
One-quarter of the studied isolates were resistant to one or more antibacillary drugs. This situation is notorious for INH resistance which was detected on 18% of the clinical isolates

Summary

Introduction

Despite the importance that the African region plays in a global TB epidemiological context, many countries still lack data on the prevalence of specific M. tuberculosis strains and drug resistance[1]. The latest World Health Organization (WHO) estimates for Angola suggest the occurrence of 90 000 new cases and an incidence rate of 370 cases per 100 000 habitants in 2014 combined with an increasing trend over the last two decades[1]. These estimates point towards the occurrence of 1500 cases of multidrug resistant (MDR) TB that were not yet bacteriologically confirmed[1]. We have characterized the genetic diversity and drug susceptibility profiles of circulating M. tuberculosis strains recovered from patients followed at a central hospital in Luanda

Methods

Results

Conclusion