MOLECULAR FINGERPRINTING OF MYCOBACTERIUM-TUBERCULOSIS AND RISK-FACTORS FOR TUBERCULOSIS TRANSMISSION IN PARIS, FRANCE, AND SURROUNDING AREA

Forty-three percent of the tuberculosis cases reported in France are f rom the Ile de France region. The incidence of tuberculosis in this re gion is 33 cases per 100,000 inhabitants, twice the national average. A restriction fragment length polymorphism (RFLP) analysis was perform ed with clinical isolates of Mycobacterium tuberculosis isolated durin g 1995 in 10 hospitals in Paris and surrounding areas to detect tuberc ulosis transmission and define the factors associated with clustering in this population. The molecular markers used were the insertion sequ ence IS6110 and the direct repeat (DR) sequence. Social, demographic, and clinical data were collected from the patients' medical files. Ten patients with isolates with a single copy of IS6110 were excluded fro m further analysis. Twenty-four patients with false-positive cultures due to laboratory contamination (based on RFLP analysis with IS6110 an d examination of patient data) were also excluded. The study was then conducted with 272 strains isolated from 27 patients. Further fingerpr inting was performed by using the DR element with strains with pattern s by RFLP analysis with IS6110 and with low numbers of copies of IS611 0. The combined use of both markers identified unique patterns for 177 strains and clustered 95 (35.7%) strains in 26 groups, each containin g isolates from 2 to 12 patients. The clustering was strongly associat ed with homelessness and the male sex. It was not associated with age, birth in a foreign country, human immunodeficiency virus positivity, or residence in hostels or prison. Isolates from homeless people were often included in large clusters, and homeless people could be the sou rce of tuberculosis transmission for more than 50% of the clustered pa tients. These results suggest that homeless people play a key role in the spread of M. tuberculosis in the community and that poor socioecon omic conditions are the main risk factors associated with active tuber culosis transmission.