A snapshot of the biodiversity and clustering of Mycobacterium tuberculosis in Oman using spoligotyping

SETTINGS: National Tuberculosis Reference Laboratory, Central Public Health Laboratory, Ministry of Health, Oman. OBJECTIVE: To use spoligotyping to explore the genetic population structure and clustering of Mycobacterium tuberculosis isolates among nationals and immigrants in Oman. METHODS: Using spoligotyping, we characterised all available isolates from 2007, and randomly selected isolates from 2005 and 2006. A total of 312 clinical isolates from the same number of patients diagnosed with tuberculosis (TB) in 2005-2007 were included in the study. RESULTS: Of 312 isolates, 69% were in clusters ranging from 2 to 38 isolates. The proportion of clustering was 58% among 2005-2006 samples and 67% among 2007 samples, with higher clustering among Omanis than among immigrants. The study showed that M. tuberculosis Indian family lineages, CAS1-Delhi, CAS and EAI5 were the predominant strains. Around 50% of the immigrants shared strains with Omanis. Twelve of the 19 INH-monoresistant strains and the two multidrug-resistant strains were in clusters (P = 0.81). CONCLUSION: This study demonstrates the predominance in Oman of the strain family commonly found on the Indian sub-continent. A high proportion of immigrant strains were in the same clusters as Omani strains. To better ascertain the transmission dynamics of M. tuberculosis, we recommend that stringent molecular and conventional epidemiological methods be applied.