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Free Content Mycobacterium tuberculosis typing: usefulness of DRE-PCR to confirm cross-contamination in the mycobacteriology laboratory of a general reference hospital for AIDS

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In this study two molecular typing methods, a simple double repetitive element PCR-based assay and the standardized restriction fragment length polymorphism (RFLP), were used to confirm cross-contamination in the mycobacteriology laboratory. Clinical specimens from 12 patients, submitted for acid-fast bacilli stain smear and processed for culture in Löwenstein-Jensen on the same day, resulted in positive bacterioscopy (+++) and confluent growth only for one of the patients. The specimens from all the other patients but two were smear-negative and culture-positive, with one or two colonies. None of them had clinical symptoms and radiological findings for active tuberculosis (TB). The suspicion of false-positive cultures arose when a health care worker who had had a PPD skin test conversion, claimed to be healthy and had no TB symptoms, was found to have a positive sputum culture. DRE-PCR demonstrated that all nine cultures typed belonged to one cluster, further confirmed by RFLP. Although DRE-PCR has been found to be poorly reproducible, it has enough discriminatory power to be useful for rapid epidemiological investigation in selected settings.

Keywords: DRE-PCR typing; Mycobacterium tuberculosis; cross-contamination

Document Type: Regular Paper

Affiliations: 1: Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, Brasil 2: Laboratório de Hanseníase, Fundação Oswaldo Cruz, Rio de Janeiro, Brasil 3: Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, Brasil

Publication date: February 1, 2002

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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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