Abstract
BackgroundPaediatric tuberculosis (TB) is poorly addressed in Ethiopia and information about its magnitude and the genotype distribution of the causative Mycobacterium tuberculosis strains responsible for its spread are scanty.MethodsGastric lavage or sputum samples were collected from consecutively enrolled TB suspect children visiting Jimma University Hospital in 2011 and cultured on Middlebrook 7H11 and Löwenstein-Jensen media. Acid fast bacterial (AFB) isolates were subjected to molecular typing targeting regions of difference (RDs), 16S rDNA gene and the direct repeat (DR) region using multiplex polymerase chain reaction (mPCR), gene sequencing and spoligotyping, respectively. Molecular drug susceptibility testing of M. tuberculosis isolates was performed by Genotype®MTBDRplus line probe assay (LPA) (Hain Life Sciences, Germany).ResultsGastric lavage (n = 43) or sputum (n = 58) samples were collected from 101 children and 31.7% (32/101) of the samples were positive for AFB by microscopy, culture and/or PCR. Out of 25 AFB isolates, 60% (15/25) were identified as M. tuberculosis by PCR, and 40% isolates (10/25) were confirmed to be non-tuberculous mycobacteria (NTM) by genus typing and 16S rDNA gene sequencing. Lineage classification assigned the M. tuberculosis strains into Euro-American (EUA, 66.7%; 10/15), East-African-Indian (EAI; 2/15), East-Asian (EA; 1/15) and Indio-Oceanic (IO; 1/15) lineages. Seven M. tuberculosis strains were new to the SpolDB4 database. All of the M. tuberculosis isolates were susceptible to isoniazid (INH) and rifampicin (RIF), except for one strain (of spoligotype SIT-149 or T3_ETH family) which had a mutation at the inhA locus which often confers resistance to INH (low level) and ethionamide.ConclusionsAnalysis of the genetic population structure of paediatric M. tuberculosis strains suggested similarity with that of adults, indicating an on-going and active transmission of M. tuberculosis from adults to children in Ethiopia. There were no multidrug-resistant TB (MDR-TB) strains among the isolates.
Highlights
Paediatric tuberculosis (TB) is poorly addressed in Ethiopia and information about its magnitude and the genotype distribution of the causative Mycobacterium tuberculosis strains responsible for its spread are scanty
Based on large sequence polymorphism, six main lineages have been described within the M. tuberculosis complex (MTBC) affecting humans: Indio-oceanic (IO) (Lineage 1), East-Asian (EA) (Lineage 2), East-African-Indian (EAI) (Lineage 3), Euro-American (EUA) (Lineage 4), West African Lineage I (Lineage 5) and West African Lineage II (Lineage 6) [13]
This study aimed to identify the genetic diversity of Mycobacterium isolates responsible for paediatric TB in Jimma University Hospital in southwest Ethiopia and compare this with already described diversity among adult Ethiopians
Summary
Paediatric tuberculosis (TB) is poorly addressed in Ethiopia and information about its magnitude and the genotype distribution of the causative Mycobacterium tuberculosis strains responsible for its spread are scanty. Addressing childhood tuberculosis is important because of the morbidity and mortality burden in children and because it is a public health measure of Molecular characterization of strains has allowed for the analysis and better understanding of transmission dynamics, genetic phylogeny, strain virulence and drug resistance [9,10]. Gagneux and Small [15] have reviewed the different terminology and the genetic markers used to assign the MTBC into different phylogeographic groupings. Once the genotype data are available, different online computer programs and databases can assist in suggesting and assigning of the MTBC strains into genetic groups using a set of mathematical rules and according to the molecular marker used [16,17,18]
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