Increased isolation of nontuberculous mycobacteria among TB suspects in Northeastern, Tanzania: public health and diagnostic implications for control programmes
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Date
2016
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Abstract
Background: Non-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.
Methods: A 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, Geno-
Type® 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.
Results: The 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 Geno-
Type® 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.
Conclusion: NTM 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
Description
BMC Res Notes 2016; Vol. 9:109
Keywords
Nontuberculous mycobacteria, Peripheral diagnostic centres, Human immunodeficiency virus, TB