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 population of southern Madrid and from all the prisons located throughout the city.

OBJECTIVE

To determine the frequency with which common strains of Mycobacterium tuberculosis cause disease among patients from both the urban and prison 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 December 1998. Risk factors that might be associated with the dissemination of common strains of TB among the two populations were also investigated.

RESULTS

Two hundred and twenty-one cases of culture-positive TB were identified, 99 (47.8%) of which were grouped in 23 clusters. Eleven were general clusters that spanned the prison and urban populations involved 69 patients (31.2%). Univariate analysis of risk factors showed that age <35 years, human immunodeficiency virus (HIV) infection, intravenous drug use and current or previous imprisonment were all associated at a statistically significant level with inclusion in general clusters. The final logistic regression model showed an interaction between HIV infection and incarceration.

CONCLUSIONS

Dissemination of common strains of M. tuberculosis between prison inmates and the urban population of Madrid is significant, and involves subjects with a history of imprisonment and HIV infection.