Effect of clinical and socio-economic factors on the rate of clustering of Mycobacterium tuberculosis clinical isolates in Elche (Spain)

We studied the association that exists between the epidemiological type clustering of isolates of Mycobacterium tuberculosis and certain clinical, epidemiological and socio-economic characteristics of tuberculosis patients in the Elche health district of Spain. A total of 144 patients diagnosed between 1993 and 1999 and whose isolates had been genotyped by IS6110-RFLP in an earlier study were included. Multivariate analysis showed that the independent variables associated with clustering of strain types were: age (1-25 years, OR 2.92, 95% CI 0.83-10.3), a high percentage of infection in the first circle of contacts (OR 2.89, 95% CI 0.96-8.68), urban dwelling (OR 2.12 95% CI 0.73-6.2), use of bronchoscopy to obtain samples (OR 16.3, 95% CI 2.3-11.5) and working contact with many people (OR 2.81, 95% CI 0.94-8.3). These data contribute to a better understanding of the epidemiology of tuberculosis and improved systems of control.