Spoligotyping of multidrug-resistant Mycobacterium tuberculosis isolates in Ethiopia

SETTING: St Peter Tuberculosis (TB) Specialized Hospital and the Aklilu Lemma Institute of Pathobiology, Addis Ababa, Ethiopia. OBJECTIVE: To genotype multidrug-resistant tuberculosis (MDR-TB) isolates and assess the magnitude of their clustering. DESIGN: A total of 183 consecutive MDR-TB isolates collected between September 2009 and February 2012 were characterised using molecular typing. Prior to the study, the isolates were confirmed as MDR-TB using GenoType® MTBDRplus. Recent transmission index was used to analyse the clusters. RESULTS: Spoligotyping identified 43 different patterns, of which 17 consisted of at least two isolates forming clusters, while 26 had only a single isolate. The most frequent patterns were spoligo international typing (SIT) number 21 and 149. Twenty-four patterns did not match existing patterns in the SpolDB4 database. The strains belonged to three lineages, the predominant lineages being Euro-American and Indo-Oceanic, each consisting of 65 isolates. High proportions (86%) of patients were infected with clustered strains, suggesting probable recent transmission of MDR-TB in the study area. CONCLUSION: The observation of cluster formation of the spoligotype patterns of MDR-TB isolates could suggest transmission of MDR-TB strains among the population, thus warranting further attention.