Molecular epidemiology of Mycobacterium tuberculosis in Lisbon

We conducted a molecular epidemiology study of Mycobacterium tuberculosis strains isolated from patients in Lisbon hospitals. We used restriction fragment length polymorphism (RFLP) to detect Lisbon family strains and to determine the genetic diversity of Mycobacterium tuberculosis strains isolated in Lisbon, through identification of the most important risk factors of tuberculosis transmission analysis, with the insertion sequence IS6110 as a probe to fingerprint isolates of Mycobacterium tuberculosis. 64.8% of the 290 Mycobacterium tuberculosis isolates were grouped in clusters. This figure was 60.7% if we excluded strains with five or fewer IS6110 copies. Multidrug-resistance was observed in 4.1% of the strains and they were all in clusters. Forty-five (18.2%) strains were included in the Lisbon family. Considering the relatively high percentage of strains in cluster detected in this study, we believe that active transmission is still taking place in Lisbon. Moreover, clusters of Lisbon strains represent the predominant strains circulating in Lisbon and are still related to drug resistance although presenting a lower percentage than that observed in previous studies.