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Abstract
BackgroundNon-tuberculous mycobacteria (NTM) are increasingly reported worldwide associated with human disease. Defining the significance of NTM in settings with endemic tuberculosis (TB) requires the discrimination of NTM from TB in suspect patients. Correct and timely identification of NTM will impact both therapy and epidemiology of TB and TB-like diseases. The present study aimed at determining the frequency and diversity of NTM among TB suspects in northeastern Tanzania.MethodsA cross-sectional study was conducted between November 2012 through January 2013. Seven hundred and forty-four sputum samples were collected from 372 TB suspects. Detection was done by using phenotypic, GenoType® Mycobacterium CM/AS kits, 16S rRNA and hsp65 gene sequencing for identification of isolates not identified by Hain kits. Binary regression model was used to analyse the predictors of NTM detection.ResultsThe prevalence of NTM was 9.7 % of the mycobacterial isolates. Out of 36 patients with confirmed NTM infection, 12 were HIV infected with HIV being a significant predictor of NTM detection (P < 0.001). Co-infection with Mycobacterium tuberculosis (M. tb) was found in five patients. Twenty-eight NTM isolates were identified using GenoType® Mycobacterium CM/AS and eight isolates could not be identified. Identified species included M. gordonae and M. interjectum 6 (16.7 %), M. intracelullare 4 (11.1 %), M. avium spp. and M. fortuitum 2 (5.5 %), M. kansasii, M. lentiflavum, M. simiae, M. celatum, M. marinum 1 (2.8 %) each. Of isolates not identified to subspecies level, we identified M. kumamotonense (2), M. intracellulare/kansasii, M. intermedium/triplex, M. acapulcensis/flavescens, M. stomatepiae, M. colombiense and M. terrae complex (1) each using 16S rRNA sequencing. Additionally, hsp65 gene sequencing identified M. kumamotonense, M. scrofulaceum/M. avium, M. avium, M. flavescens/novocastrense, M. kumamotonense/hiberniae, M. lentiflavum, M. colombiense/M. avium and M. kumamotonense/terrae/hiberniae (1) each. Results of the 16S rRNA and hsp65 gene sequencing were concordant in three and discordant in five isolates not identified by GenoType® Mycobacterium CM/AS.ConclusionNTM infections may play a vital role in causing lung disease and impact management of TB in endemic settings. GenoType® Mycobacterium CM/AS represents a useful tool to identify clinical NTM infections. However, 16S rRNA gene sequencing should be thought for confirmatory diagnosis of the clinical isolates. Due to the complexity and inconsistence of NTM identification, we recommend diagnosis of NTM infections be centralized by strengthening and setting up quality national and regional infrastructure.
Highlights
Non-tuberculous mycobacteria (NTM) are increasingly reported worldwide associated with human disease
A total of 744 sputum samples were collected from 372 TB suspects who self–presented at two peripheral diagnostic centres (PDCs) and two hospitals in Tanga, northeastern, Tanzania
The overall frequency of the patients with NTM in the study was 9.7 %; Human immunodeficiency virus (HIV) positivity was found to be associated with NTM infection among the factors analysed, with a statistical significance of
Summary
Non-tuberculous mycobacteria (NTM) are increasingly reported worldwide associated with human disease. Defining the epidemiology of NTM diseases in most resource poor settings like Tanzania is more challenging than its well documented relative Mycobacterium tuberculosis complex (MTC) [2]. Due to their ubiquitous presence in the environment, exposure to NTM is likely common, as they can colonize the respiratory tract without causing disease such that finding NTM in respiratory secretions does not necessarily have clinical implications in all patients [3,4,5]. NTM are becoming recognized as true pathogens and important causes of human infections [6, 7]
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