A total of 169 clinical isolates of
M. tuberculosis were obtained from 169 TB patients residing in Tochigi Prefecture. In Japan, the Law Concerning the Prevention of Infections and Medical Care for Patients of Infections mandates that local public health institutions, such as the Tochigi Prefectural Institute of Public Health and Environmental Science (Tochigi IPH), collect all
M. tuberculosis isolates obtained from TB patients, as well as anonymized clinical information about these patients. The Tochigi IPH began to collect
M. tuberculosis clinical isolates in 2007. Isolates obtained in 2007 and in 2013 were therefore analyzed in this study. Of the 169 patients, 31, including one foreign-born patient, were living in the northern part of Tochigi; 83, including 13 foreign-born patients, were living in the central part; and 55, including seven foreign-born patients, were living in the southern part (Additional file
2: Table S1). Of these isolates, 87 and 82 were isolated in 2007 and 2013, respectively (Table
1). Of the 87 isolates obtained in 2007, 11 (12.6%) were from foreign-born patients (Table
1) and 60 (69.0%) were from males (Additional file
3: Table S2). Of the 82 isolates obtained in 2013, 10 (12.2%) were from foreign-born patients (Table
1) and 44 (53.7%) were from males (Additional file
3: Table S2). The average age of the 169 patients was 62.7 years (range, 1.7–98.5 years), 37.9 years for patients with
M. tuberculosis Lineage 1; 69.4 and 57.1 years for patients with Ancestral and Modern Lineage 2, respectively; 35.1 years for patients with Lineage 3; and 63.3 years for patients with Lineage 4 (Fig.
4). The 21 foreign-born patients (Table
1, parentheses) were from nine countries/regions, including four each from Taiwan and the Philippines; three from Korea; two each from China, Nepal, Peru, and Thailand; and one each from Brazil and Vietnam. Information about patients and isolates, including dates and countries/regions of birth, gender, areas of residence, and results of drug susceptibility testing, was obtained from the National Epidemiological Surveillance of Infectious Diseases (NESID), an active infectious disease surveillance system in Japan that collects reports about patients with various infectious diseases [
16].
Table 1
Lineage distribution of M. tuberculosis isolates in 2007 and 2013
Total | 13 (9) | 111 (4) | 2 (2) | 43 (6) | 169 (21) |
79 (3) | 32 (1) |
2007 | 8 (5) [9.2%] | 44 (3) [50.6%] | 13 (0) [14.9%] | 0 (0) [0.0%] | 22 (3) [25.3%] | 87 (11) [100.0%] |
2013 | 5 (4) [6.1%] | 35 (0) [42.7%] | 19 (1) [23.2%] | 2 (2) [2.4%] | 21 (3) [25.6%] | 82 (10) [100.0%] |