Transmission of tuberculosis among the urban homeless

Objective. - To determine the relative frequencies of primary and reactivation tuberculosis in the urban homeless. Design. - Prospective evaluation of homeless tuberculosis patients. Setting. - Central Los Angeles, Calif. Patients. - Thirty-four homeless patients with culture-proven tuberculosis. Interventions. - IS61 10-based restriction fragment length polymorphism (RFLP) analysis was performed on Mycobacterium tuberculosis isolates. If results were inconclusive, pTBN12-based RFLP analysis was performed. Main Outcome Measure. - Clustering of M tuberculosis isolates. A cluster consisted of two or more isolates with indistinguishable RFLP patterns. Results. - Twenty-four of 34 homeless patients had clustered isolates in six clusters. Conclusions. - The minimum percentage of cases due to primary tuberculosis in the homeless was estimated to be 53%, compared with the traditional estimate of 10% in the general population. The results suggest that primary tuberculosis caused the majority of tuberculosis cases in this population of the urban homeless in central Los Angeles.