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: IS6110-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.