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Free Content Extensive transmission of an isoniazid-resistant strain of Mycobacterium tuberculosis in Sweden

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SETTING: City of Stockholm, Sweden.

BACKGROUND: The incidence of tuberculosis (TB) in Sweden increased by 40% between 2003 and 2005. The spread of a unique TB strain resistant to isoniazid (INH) contributed to this increase.

OBJECTIVE: To describe outbreaks of TB caused by this single strain, elucidate possible causes for its extensive spread and identify shortcomings of the TB control programme in Sweden.

RESULTS: We identified a cluster consisting of 102 culture-confirmed TB cases with identical DNA fingerprints and 26 epidemiologically related cases, not confirmed by culture, all diagnosed between 1996 and 2005. Five partly separate outbreaks of this strain were discovered. Epidemiological links were established for 56% of the culture-confirmed cases and for all cases not confirmed by culture. Three patients died while receiving treatment, four became failures and eight defaulted or were lost to follow-up. Only eight patients received directly observed treatment (DOT) up to a period of 3 months, although 40% had poor adherence.

CONCLUSIONS: Shortcomings of the national TB programme were revealed. Improved contact tracing and case holding, including DOT, is crucial to reduce TB transmission in Sweden.

Keywords: adherence; cluster; isoniazid resistance; outbreak; transmission; tuberculosis

Document Type: Regular Paper

Affiliations: 1: Infectious Diseases Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Solna, Sweden 2: Department of Communicable Diseases Control and Prevention, Stockholm, Sweden 3: Swedish Institute for Infectious Disease Control, Solna, Sweden 4: Department of Paediatrics, Astrid Lindgren Childrens' Hospital, Karolinska University Hospital, Solna, Sweden 5: Department of Clinical Microbiology, Karolinska University Hospital, Solna, Sweden

Publication date: February 1, 2008

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  • The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

    Certain IJTLD articles are selected for translation into French, Spanish, Chinese or Russian. They are available on the Union website

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