Molecular epidemiology of Mycobacterium tuberculosis in patients of Somalian and white ethnic origin attending an inner London clinic

BACKGROUND: In 2002, 6891 and 2850 tuberculosis (TB) notifications were received respectively for England and Wales and London. TB is an important public health problem in the Somalian population of inner London. SETTING: An inner London TB clinic. OBJECTIVE: To study the epidemiology, genetic diversity and clustering of tuberculosis in Somalian and white patients. MAIN OUTCOME METHODS: In a cross sectional study from June 1998 to June 2001, IS6110 restriction fragment length polymorphism (RFLP) and secondary spoligotyping was performed on 57 M. tuberculosis isolates from 40 Somalian and 17 white patients. Contact tracing of patients provided epidemiological information. RESULTS: In the Somalian group, using RFLP and spoligotyping, there were three clusters. Routine contact tracing confirmed one household cluster (two siblings). Spoligotyping yielded one cluster of two white patients who were patrons of a local pub. The rates of recent transmission were respectively 10.0% and 5.9% in the Somalian and white groups. CONCLUSIONS: Heterogeneous RFLP patterns in both groups showed a predominance of reactivation disease. Clustering as evidence of recent transmission has public health implications for enhanced contact tracing and active intervention.