[Transmission of tuberculosis in Gironde: epidemiologic investigation by genomic analysis of Mycobacterium tuberculosis].

Background: Over the past few years, epidemiologic surveys of tuberculosis have been strengthened by new biologic technology, in particularly using RFLP (Restriction Fragment Length Polymorphism). This technique, which identifies Mycobacterium tuberculosis patterns, has allowed to study thoroughly tuberculosis bacilli transmission and pathogenesis. First applied on tuberculosis epidemics in at risk groups, RFLP has now an interest in the epidemiologic molecular survey of urbans populations. The aim of this study is to identify, in a French department, the proportion of clustering cases of tuberculosis, suspected of recent contamination.

Methods: An active surveillance of tuberculosis allows to record systematically the cases of tuberculosis-disease in Gironde. All M. tuberculosis isolates from the patients reported in this surveillance system were processed through IS6110 based RFLP analysis. Patients were interviewed face to face before this analysis, using a standardised data collection instrument.

Results: 102 patients were included in 1997; the RFLP analysis of all available strains identifies a high degree of polymorphism with 71 unique patterns; twelve groups with clustering patterns were found, grouping two (nine clusters), three (two clusters) and seven patients (one cluster) each. Those cases suspected of recent transmission were younger (age<60 years) and lived in poorer conditions. Epidemiologic links were confirmed in only 35% of the 31 patients clustered.

Conclusion: This community survey analysis has allowed to identify at risk groups for tuberculosis transmission and to strengthen tuberculosis control in Gironde.