Department of Epidemiology and Clinical Research, The Research Institute of Tuberculosis, Kiyose, Japan.
Department of Mycobacterium Reference and Research, The Research Institute of Tuberculosis, Kiyose, Japan.
BMJ Open. 2019 May 9;9(5):e029295. doi: 10.1136/bmjopen-2019-029295.
Molecular epidemiology is a promising tool for understanding tuberculosis transmission dynamics but has not been sufficiently utilised in Asian countries including Japan. The aim of this study was to estimate the proportion of TB cases attributable to recent transmission and to identify risk factors of genotype clustering and the development of large clusters within 3 years in an urban setting in Japan.
Long-term cross-sectional observational study combining the characteristics of patients with culture-positive TB notified in Shinjuku City, Tokyo (2002-2013), with genotype data of PRIMARY OUTCOME MEASURE: Genotype clustering rate and association between genotype clustering status and explanatory variables.
Among 1025 cases, 515 were localised within 113 genotype clusters. The overall clustering rate was 39.2%. Significantly higher rates were found in patients aged <40 years (adjusted odds ratio (aOR)=1.73, 95% CI 1.23 to 2.44), native Japanese individuals (aOR=3.90, 95% CI 2.27 to 6.72), full-time workers (aOR=1.63, 95% CI 1.17 to 2.27), part-time/daily workers (aOR=2.20, 95% CI 1.35 to 3.58), individuals receiving public assistance (aOR=1.81, 95% CI 1.15 to 2.84) and homeless people (aOR=1.63, 95% CI 1.02 to 2.62). A significant predictor of large genotype clusters within 3 years was a registration interval ≤2 months between the first two cases in a cluster.
Our results indicated that a large proportion of patients with culture-positive TB were involved in the recent TB transmission chain. Foreign-born persons still have a limited impact on transmission in the Japanese urban setting. Intensified public health interventions, including the active case finding, need to focus on individuals with socioeconomic risk factors that are significantly associated with tuberculosis transmission and clusters with shorter registration intervals between the first two cases.
分子流行病学是了解结核病传播动态的一种很有前途的工具，但在包括日本在内的亚洲国家尚未得到充分利用。本研究的目的是估计结核病病例归因于近期传播的比例，并确定在日本城市环境中，3 年内基因型聚类的风险因素和大型聚类的发展。
长期横断面观察性研究，结合东京新宿区报告的培养阳性结核病患者的特征（2002-2013 年）与基因型数据，主要观察指标：基因型聚类率和基因型聚类状态与解释变量之间的关联。
在 1025 例病例中，515 例位于 113 个基因型聚类内。总体聚类率为 39.2%。年龄<40 岁（调整优势比[aOR]=1.73，95%CI 1.23-2.44）、日本本土人（aOR=3.90，95%CI 2.27-6.72）、全职工作者（aOR=1.63，95%CI 1.17-2.27）、兼职/日工（aOR=2.20，95%CI 1.35-3.58）、接受公共援助者（aOR=1.81，95%CI 1.15-2.84）和无家可归者（aOR=1.63，95%CI 1.02-2.62）的患者聚类率显著较高。3 年内大型基因型聚类的显著预测因子是聚类中前两个病例的登记间隔≤2 个月。
我们的结果表明，很大一部分培养阳性结核病患者都参与了近期结核病传播链。在日本城市环境中，外来出生者对传播的影响仍然有限。需要加强公共卫生干预措施，包括积极发现病例，重点关注与结核病传播和前两个病例登记间隔较短的聚类有显著关联的具有社会经济风险因素的个体。
