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Transmission of tuberculosis among the urban homeless
P F Barnes1, H el-Hajj, S Preston-Martin
1Department of Medicine, University of Southern California School of Medicine, Los Angeles 90033, USA.
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.