Background: The transmission of tuberculosis may affect the incidence rate of the disease in Poland. Genetic methods are of assistance in tracing the infection transmission, identifying its sources, determining the risk groups, and focusing on the preventive actions.
Objectives: The objectives of this study lie in an assessment of tuberculosis transmission by genetic methods with the assistance of the standard epidemiologic interview.
Methods: The genome DNA of 275 Mycobacterium tuberculosis (Mtb) strains from tuberculosis patients, inhabitants of the city of Krakow, was subjected to a genetic analysis via the spoligotyping method and the IS6110-Mtb1-Mtb2 polymerase chain reaction (PCR) method. If the DNA profiles were identical in both of the PCRs, they were considered identical and classified within one molecular family.
Results: Among 275 strains, 104 genetic patterns (spoligotypes) were identified. Two hundred and three strains were divided into 66 molecular families (clusters) and analyzed with the IS6110- Mtb1-Mtb2 PCR method. Eighteen clusters were separated. In the Mtb1-Mtb2 clusters, 21 patients were in the risk groups (the homeless, prisoners, and nursing home residents). We did not confirm any direct or temporary contacts between the patients constituting the Mtb1-Mtb2 clusters (apart from the risk groups). However, the patients in these clusters often lived in the same parts of Krakow.
Conclusions: The standard epidemiologic interview in tuberculosis patients should be combined with genetic methods. Active transmission of tuberculosis occurs largely among the individuals maintaining probably periodic contacts. The patients who are in the risk groups may play an important role in the transmission of tuberculosis.
Keywords: Cluster; risk groups; spoligotyping; transmission; tuberculosis.