MOLECULAR EPIDEMIOLOGY OF MYCOBACTERIUM-TUBERCULOSIS STRAINS ISOLATEDDURING A 3-YEAR PERIOD (1993 TO 1995) IN SEVILLE, SPAIN

The genetic polymorphism of Mycobacterium tuberculosis strains isolate d in Seville, Spain, was studied by using computer-assisted analysis o f the IS6110 fingerprint in order to determine the current situation a nd to evaluate the human-to-human transmission of this pathogen. One h undred seventy-six isolates from 175 patients among the 205 patients d iagnosed with tuberculosis (TB) during a 3-year period (1993 to 1995) were cultured and analyzed. One hundred nine patients (62%) were infec ted with genetically different isolates, and 67 isolates (38%) were gr ouped into 19 clusters. These results demonstrate that the level of cl ustering of strains in Seville is intermediate between those in develo ped and developing countries. Epidemiological relatedness was shown fo r isolates from only la of these clusters. Active and high transmissio n rates exist in children and in human immunodeficiency virus (HIV)-in fected adults, while in non-HIV-infected adults this transmission rate is moderate, Although transmission from children to adults is uncommo n, the probability of transmission from HIV-infected patients to young adults not infected with HIV may be higher, On the basis of these obs ervations, wt predict a constant rise in the rate of TB transmission a mong HIV-infected patients and probably in young adult patients not in fected with HIV if measures for the effective prevention of TB among t he HIV-infected population are not implemented.