Background: A molecular epidemiological study of TB conducted in North Sardinia (Italy) by Micobacteriology’s laboratory (University of Sassari), demonstrated an interesting case of same-strain transmission among co-workers. Epidemiological information indicating possible links between 5 TB-patients, hospitalized in the Institute of Respiratory Disease (University of Sassari), were also available. The patients come from the same geographic area, and moreover they were co-workers and friends which met each other frequently.
Case Report: Isolation, identification and Drug susceptibility testing of strains and IS6110-based RFLP analysis to demonstrate the same origin of the Mycobacterium tuberculosis strains were performed in the Department of Biomedical Science, University of Sassari. All the strains were primary resistant to Isoniazid and Streptomicin and were genetically indistinguishable by direct comparison of the IS6110-patterns, that was constituted by 9 copies of the IS6110 insertion element.
Conclusions: The combination of cavitary disease, high MTB sputum concentration and close proximity resulted in a strong infecting capacity of the IC in this outbreak, while the environment and the clinical characteristics of each case were considered as the most important factors responsible for the variability in developing active TB.

Keywords: Drug – resistant tuberculosis, Mycobacterium tuberculosis, tuberculosis transmission