[Objectives] Japan Anti-Tuberculosis Association (JATA) (12)-variable numbers of tandem repeats (VNTR) is a standard method for genotyping of clinical isolates of Mycobacterium tuberculosis in Japan. As a model study for nationwide surveillance, this study aimed to describe the tendency and frequency of genotypes of M.tuberculosis in a large number of clinical samples. [Methods] Clinical isolates of M.tuberculosis (n＝1,778) were obtained from patients with tuberculosis in 3 areas, i.e., Osaka City, Osaka Prefecture, and Kobe City, during 2007 and 2008. The samples were analyzed using JATA (12)-VNTR. All genotypes were subjected to clustering analysis. [Results and Discussion] In total, 1,086 (61.1％) isolates showed clustering. The most common clusters were composed of 3 members. Such clusters were considered to reflect either actual transmission or low discriminatory power of JATA (12)-VNTR. Several prevalent JATA(12)-VNTR genotypes formed large clusters and were discussed in relation with epidemiological findings of other studies. The findings of this study will aid in the construction of an effective genotypingbased surveillance system of M.tuberculosis, through improvement of interpretation of VNTR types, observation of certain particular strains in an area, and efficient detection of unidentified outbreaks.

[Objectives] To evaluate the usefulness of the JATA (12)-variable number of tandem repeats (VNTR) system for identifying the source of Mycobacterium tuberculosis outbreaks. [Design] JATA(12)-VNTR genotyping was performed on M.tuberculosis isolates from a total of 206 patients in whom group infection was confirmed by epidemiological studies ("group infection"), as well as from 64 patient clusters in whom group infection was suspected but not confirmed ("non-group infection"). The patients were diagnosed in Osaka Prefecture from April 1999 to December 2011. [Results] All isolates from the "non-group infection" patients showed a unique VNTR pattern, whereas isolates from 185 (89.9％) "group infection" patients showed a common and group-specific JATA (12)-VNTR pattern. However, single-locus variants were observed in 1 (1.6％) "non-group infection" case and in 21 (10.2％) "group infection" cases. [Conclusion] Tuberculosis in 248 (91.9％) of the 270 study patients could be correctly identified based on the genotyping of the isolates by using the JATA (12)-VNTR. If proper attention is paid to the single-locus variant, the JATA (12)-VNTR system would be a useful tool for identification of sources of tuberculosis outbreaks.

[Objective] The QuantiFERON^®-TB (QFT) blood test is the major tool for the diagnosis of Mycobacterium tuberculosis (TB) infection among healthcare workers (HCWs). We used QFT tests to estimate the prevalence of TB infection among HCWs in our hospital. [Material and Methods] Between 2003 and 2010, a total of 733 HCWs were enrolled in this study, and the prevalence of TB infection was analyzed according to the HCWs jobs and work place. [Results] Among the 152 men and 581 women who were evaluated, 3 female HCWs had a history of TB. Fifty-eight HCWs (8 men and 50 women with a mean age of 56.3 years and 48.4 years, respectively) demonstrated positive QFT tests. The positive rate was 7.9％ for all staff members throughout the study period. The QFT test was positive for 1 HCW who was treated for TB in 1998, and negative and inconclusive for 2 other HCWs treated for TB in 2002. The positive rate for QFT was 16.0％ in the TB ward (12/75, 95％ confidence interval [CI]: 7.7- 24.3％), 9.9％ in the other wards (22/222, 95％ CI: 7.9-11.9), and 1.1％ in the outpatient department (1/91, 95％ CI: 0-2.2). According to the job category, the QFT positive rates were as follows: doctors, 4.3％ (3/70, 95％ CI: 1.9-6.7); nurses, 10.3 ％ (27/263, 95％ CI: 8.4-12.2); radiology technicians, 20.0％ (3/15, 95％ CI: 9.7-30.3); laboratory technicians, 11.4％ (4/35, 95％ CI: 6.0-16.8). The positive rate among doctors working in the TB ward was 10.0％, and that for nurses was 24.3％. This indicates that the prevalence of infection among HCWs in the TB ward was significantly higher than that in other work places. A comparison of the results from 2003 through 2007 revealed that for a total of 307 workers, 90.6％ and 5.2％ remained negative and positive, respectively, while 1.6％ converted from negative to positive, and 2.6％ from positive to negative. [Conclusion] The positive rate among HCWs in the TB ward was higher than that in other wards. This is especially remarkable for doctors and nurses working in the TB ward.

[Objectives & Subjects] The change in IGRA (interferon-gamma release assay, with QuantiFERON-TB^® Gold, QFT) responses was followed up for one year in a group of contacts of healthcare workers who had been exposed to tuberculosis (TB) infection for a relatively short period in a hospital. The observation was made of a total of 59 close contacts of the index case, where 16 showed positive QFT-conversion and 7 showed the intermediate response ranging 0.1 to 0.35 IU/mL. Three of the conversion cases developed active TB. [Results] 67％ of the QFT conversions occurred within 2 months of exposure and the others between 2 to 9 months. Those having converted later than 2 months after the exposure showed generally weaker QFT responses than the earlier converters. In response to the treatment to converters (either to latent TB infection or to active TB), 80％ of the cases reversed to negative or intermediate. The geometric means of the response values for ESAT-6 and CFP-10 also showed significant decline over the treatment time. [Discussions] The time profile of responses in the intermediate responders revealed an obviously distinct pattern from that of the negative responders with the values remaining uniformly at very low level throughout, which suggests that this group includes somehow exceptional responders either with or without infection.