The influence of HIV infection and imprisonment on dissemination of Mycobacterium tuberculosis in a large Spanish city

SETTING: Culture-positive cases of tuberculosis (TB) from the urban populat ion of southern Madrid and from all the prisons located throughout the city . OBJECTIVE: To determine the frequency with which common strains of Mycobact erium tuberculosis cause disease among patients from both the urban and pri son populations of a large Spanish city. DESIGN: Restriction fragment length polymorphism analysis was performed on culture-positive cases of TB identified between 1 January 1997 and 31 Decem ber 1998. Risk factors that might be associated with the dissemination of c ommon strains of TB among the two populations were also investigated. RESULTS: Two hundred and twenty-one cases of culture-positive TB were ident ified, 99 (47.8%) of which were grouped in 23 clusters. Eleven were general clusters that spanned the prison and urban populations involved 69 patient s (31.2%). Univariate analysis of risk factors showed that age < 35 years, human immunodeficiency virus (HI-V) infection, intravenous drug use and cur rent or previous imprisonment were all associated at a statistically signif icant level with inclusion in general clusters. The final logistic regressi on model showed an interaction between HIV infection and incarceration. CONCLUSIONS: Dissemination of common strains of M. tuberculosis between pri son inmates and the urban population of Madrid is significant, and involves subjects with a history of imprisonment and HIV infection.