Tuberculosis reinfection and relapse in eastern China: a prospective study using whole-genome sequencing

Objectives Tuberculosis recurrence after an initial successful treatment episode can occur from either reinfection or relapse. In a population-based sample and whole genome sequencing in eastern China, we aimed to evaluate risk factors for tuberculosis recurrence and assess the proportion of recurrence because of either reinfection or relapse. Methods Successfully treated pulmonary tuberculosis patients with sputum culture positive results were recruited from five cities in Jiangsu Province from 2013 to 2015 and followed for 2 years for tuberculosis recurrence. Among patients developing a second tuberculosis episode, whole genome sequencing was performed to distinguish relapse or reinfection through a distance threshold of 6-single-nucleotide polymorphisms. We analyzed risk factors for recurrence and epidemiological characteristics of different types of recurrent patients. Results Of 1897 successfully treated tuberculosis patients, 7.4% (141/1879) developed recurrent tuberculosis. Compared with nonrecurrent tuberculosis, patients were at higher risk of recurrence in older age (adjusted odds ratio, 1.02 for each additional year; 95% CI, 1.01 to 1.03, p = 0.003), patients previously treated for tuberculosis (adjusted odds ratio = 2.22; 95% CI, 1.52 to 3.26, p < 0.001), or with bilateral cavities (adjusted odds ratio, 1.56; 95% CI, 1.05 to 2.32, p = 0.029). Among 27.0% (38/141) recurrent tuberculosis patients with successfully sequenced pairs, relapse was substantially more common than reinfection (71.1% vs 28.9%, p = 0.014). Discussion Endogenous relapse was significantly more common than exogenous reinfection in the first 2 years after treatment in eastern China. Prioritization of high-risk groups for recurrence, such as the elderly, with a previous tuberculosis diagnosis, or with bilateral cavities, may provide opportunities to reduce post-tuberculosis morbidity.