Abstract: Objective To study latentMycobacterium tuberculosisinfection in TB professionals and those who in close contact with TB patients by γ-interferon secretory reaction.   Methods All subjects were divided into three groups: Group 1 included 128 TB professionals (60 physicians and 68 nurses). Group 2 included 60 household close contacts of TB patients. Group 3 included 40 subjects without close contact with TB patients. T-SPOT.TB (Oxford Immunotec, Abingdon, UK) was used to assay the immune reactions of peripheral blood lymphocytes to two special secreted proteins ofMycobacterium tuberculosis : 6-kDa early secreted antigenic target (ESAT-6) and culture filtrate protein 10 (CFP-10).   Results Positive rate in TB professionals, household close contacts and those who have no close contact with TB patients were 14.8% (19/128), 23.3% (14/60) and 5.0% (2/40) respectively. The positive rate of group 2 was significantly higher than that of group 3 (χ²=6.002, P=0.023). The positive rate of group 1 was higher than that of group 2 although the difference was not statistically significant. The positive rate of senior TB professionals who have worked for at least 3 years was 27.12% (16/59), this was significantly higher than that (5.0%,  2/40 ) of group 3［χ²=7.840,P=0.007;RR=5.42 (95%CI=1.32～22.31)］.  Conclusion TB professionals and those who in close contact with TB patients are at higher risk of latentMycobacterium tuberculosisinfection and it has positive correlation with contact duration.

Key words: tuberculosis/transmission, disease transmission,patient-to-professional, immunoenzyme techniques, interferon typy Ⅱ