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 RF LP (Restriction Fragment Length Polymorphism). This technique, which identi fies Mycobacterium tuberculosis patterns, has allowed to study thoroughly t uberculosis bacilli transmission and pathogenesis. First applied on tubercu losis epidemics in at risk groups, RFLP has now an interest in the epidemio logic molecular survey of urbans populations. The aim of this study is to i dentify, in a French department, the proportion of clustering cases of tube rculosis, suspected of recent contamination. Methods: An active surveillance of tuberculosis allows to record systematic ally the cases of tuberculosis-disease in Gironde. All M, tuberculosis isol ates from the patients reported in this surveillance system were processed through IS6110 based RFLP analysis. patients were interview face to face be fore this analysis, using a standardised data collection instrument. Results: 102 patients were included in 1997; the RFLP analysis of all avail able strains identifies a high degree of polymorphism with 71 unique patter ns; twelve groups with clustering patterns were found, grouping two (nine c lusters), three (two clusters) and seven patients (one cluster) each. Those cases suspected of recent transmission were younger (age < 60 years) and l ived in poorer conditions. Epidemiologic links were confirmed in only 35% o f the 31 patients clustered. Conclusion : This community survey analysis has allowed to identify, at ris k groups for tuberculosis transmission and to strengthen tuberculosis contr ol in Gironde.