Molecular epidemiology and drug resistance patterns of Mycobacterium tuberculosis complex isolates from university students and the local community in Eastern Ethiopia

Abstract

BackgroundPrevious studies suggest the burden of pulmonary tuberculosis (PTB) in Ethiopia may be greater in university students relative to the overall population. However, little is known about the transmission dynamics of PTB among students and members of the communities surrounding university campuses in Eastern Ethiopia.MethodsA cross sectional study was conducted in Eastern Ethiopia among prevalent culture-confirmed PTB cases from university students (n = 36) and community members diagnosed at one of four hospitals (n = 152) serving the surrounding area. Drug susceptibility testing (DST) was performed on Mycobacterium tuberculosis complex (MTBC) isolates using BD Bactec MGIT 960 and molecular genotyping was performed using spoligotyping and 24-loci MIRU-VNTR. MTBC strains with Identical genotyping patterns were assigned to molecular clusters as surrogate marker for recent transmission and further contact tracing was initiated among clustered patients.ResultsAmong all study participants, four MTBC lineages and 11 sub-lineages were identified, with Ethiopia_3 (Euro-American lineage) being most common sub-lineage (29.4%) in both cohorts and associated with strain clustering (P = 0.016). We further identified 13 (8.1%) strains phylogenetically closely related to Ethiopia_3 but with a distinct Spoligotyping pattern and designated as Ethiopia_4. The clustering rate of MTBC strains was 52.9% for university students and 66.7% for community members with a Recent Transmission Index (RTI) of 17.6% and 48.4%, respectively. Female gender, urban residence, and new TB cases were significantly associated with strain clustering (P<0.05). Forty-eight (30%) of the study participants were resistant to one or more first line anti TB drugs, three patients were classified as multidrug resistant (MDR).ConclusionWe found evidence for recent transmission of PTB among Ethiopian university students and the local community in Eastern Ethiopia, mainly linked to strains classified as Ethiopia_3 sub lineage. Drug resistance didn’t have a major impact on recent transmission but comprehensive molecular surveillance in combination with drug resistance profiling of MTBC strains is desirable to better characterize TB transmission dynamics in high risk congregate living environments such as university campuses and guide regional TB control programs.

Phenotypic and genotypic drug sensitivity profiles of Mycobacterium tuberculosis infection and associated factors in northeastern Ethiopia

“…The 15.9% (11/69) drug resistant detection rate using BACTEC MGIT 960 in this study was at greater proportion than similar studies [ 30 , 31 ]. On the contrary, less proportion of drug resistances were reported in this study than other research reports by using the same detection system [ 32 , 33 ] which might be due to different study areas and sample size. Most of the isolates detected as resistant by LPA were also resistant by MGIT.…”

Molecular epidemiology of tuberculosis in northeastern Ethiopia

“…In agreement with previous studies, the predominance of lineage 3 (Delhi/CAS; 32.1%) using MIRU-VNTR 24-loci genotyping showed its wide distribution throughout the country [10,50,51]. On the contrary, it was not the predominant strain rather H37Rv like and Ethiopia_3 were the most common sub-lineages in studies from prisoners and communities in Southern, Southwestern and Southeastern Ethiopia [52] and Eastern Ethiopia [32], respectively. This revealed that the overall predominant lineage of M. tb across the country varries.…”

“…The variation of spoligotype clustering in this study in comparison to many other reports might be due to the differences in geographical study settings. There were higher clustering rates reported from most studies in Ethiopia [30,32,33]. Similarly, studies outside of the country also reported greater proportion of clusters [34][35][36][37] than the overall clustering rate of this study 20.2% (21/104) which might be due to the poor recovery rate of smear positive bacteria on LJ-culture.…”

“…The lowest clustering rate by spoligotyping and absence of clustering at all in MIRU-VNTR of this study is an indication of minor or no recent transmission of the Mycobacterium in the area, which implies that the disease is mainly due to endogenous reactivation of the latent TB infection. Similarly, other studies also showed that the clustering rate of MIRU-VNTR is less than that of spoligotyping [32,35,47,48]. Those clustering rate differences in different study areas might be due to the differences in the geography, population density and socio-economic diversity [49].…”

Epidemiology of Mycobacterium tuberculosis lineages and strain clustering within urban and peri-urban settings in Ethiopia

“…In other words, successful transmission of particular genotypes has been reflected through an increase in the frequency and consistency of strain domination over time in defined populations [16,23]. However, despite recently developed advanced molecular diagnostic tools, both the nature of genotype variations and the characteristics of the host immune response to certain types of M. tb strains are largely unknown in many TB high burden settings [24,25]. Particularly in countries like Ethiopia, where there is high prevalence and high transmission rate and a diversified population of bacterial species [26-29], molecular identification of the agents can be an important component of the knowledge base required to improve on previous achievements of the national TB control program.…”