Mycobacterium tuberculosis Transmission in a Country with Low Tuberculosis Incidence: Role of Immigration and HIV Infection

Abstract

Mycobacterium tuberculosis Transmission in a Country with Low Tuberculosis Incidence: Role of Immigration and HIV Infection Lukas Fenner a , Sebastien Gagneux b , c , Peter Helbling d , Manuel Battegay e , Hans L. Rieder f , s , Gaby E. Pfyffer g , Marcel Zwahlen a , Hansjakob Furrer h , Hans H. Siegrist i , Jan Fehr j , Marisa Dolina k , Alexandra Calmy l , David Stucki b , c , Katia Jaton m , Jean-Paul Janssens n , Jesica Mazza Stalder o , Thomas Bodmer p , Beatrice Ninet q , Erik C. Böttger r and Matthias Egger a for the Swiss HIV Cohort and Molecular Epidemiology of Tuberculosis Study Groups a Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland b Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland c University of Basel, Basel, Switzerland d Division of Communicable Diseases, Federal Office of Public Health, Bern, Switzerland e Division of Infectious Diseases and Hospital Epidemiology, University Hospital of Basel, Basel, Switzerland f Institute of Social and Preventive Medicine, University of Zurich, Zurich, Switzerland s The Union, Paris, France g Department of Medical Microbiology, Luzerner Kantonsspital, Lucerne, Switzerland h Clinic for Infectious Diseases, Bern University Hospital and University of Bern, Bern, Switzerland i ADMed Microbiology, La Chaux-de-Fonds, Switzerland j Division of Infectious Diseases, University Hospital Zurich, and University of Zurich, Zurich, Switzerland k Cantonal Institute of Microbiology, Bellinzona, Switzerland l Division of Infectious Diseases, University Hospital Geneva, Geneva, Switzerland m Institute of Microbiology, University Hospital of Lausanne, Lausanne, Switzerland n Division of Pneumology, University Hospital Geneva, Geneval, Switzerland o Division of Pneumology, University Hospital Lausanne, Lausanne, Switzerland p Mycobacteriology Unit, Institute for Infectious Diseases, University of Bern, Bern, Switzerland q Laboratory of Bacteriology, University Hospital of Geneva, Geneva, Switzerland r Institute of Medical Microbiology, National Center for Mycobacteria, University of Zurich, Zurich, Switzerland ABSTRACT Immigrants from high-burden countries and HIV-coinfected individuals are risk groups for tuberculosis (TB) in countries with low TB incidence. Therefore, we studied their role in transmission of Mycobacterium tuberculosis in Switzerland. We included all TB patients from the Swiss HIV Cohort and a sample of patients from the national TB registry. We identified molecular clusters by spoligotyping and mycobacterial interspersed repetitive-unit–variable-number tandem-repeat (MIRU-VNTR) analysis and used weighted logistic regression adjusted for age and sex to identify risk factors for clustering, taking sampling proportions into account. In total, we analyzed 520 TB cases diagnosed between 2000 and 2008; 401 were foreign born, and 113 were HIV coinfected. The Euro-American M. tuberculosis lineage dominated throughout the study period (378 strains; 72.7%), with no evidence for another lineage, such as the Beijing genotype, emerging. We identified 35 molecular clusters with 90 patients, indicating recent transmission; 31 clusters involved foreign-born patients, and 15 involved HIV-infected patients. Birth origin was not associated with clustering (adjusted odds ratio (aOR), 1.58; 95% confidence interval (CI), 0.73 to 3.43; P = 0.25, comparing Swiss-born with foreign-born patients), but clustering was reduced in HIV-infected patients (aOR, 0.49; 95% CI, 0.26 to 0.93; P = 0.030). Cavitary disease, male sex, and younger age were all associated with molecular clustering. In conclusion, most TB patients in Switzerland were foreign born, but transmission of M. tuberculosis was not more common among immigrants and was reduced in HIV-infected patients followed up in the national HIV cohort study. Continued access to health services and clinical follow-up will be essential to control TB in this population.