Mycobacterium tuberculosis infection status and associated factors among household close contacts of rifampicin-resistant pulmonary tuberculosis patients: A single-center cross-sectional study

Abstract

Background

Rifampicin-resistant tuberculosis (RR-TB) is a major global public health challenge. Household close contacts (HHCs) of RR-TB patients face a high risk of Mycobacterium tuberculosis infection. Southwestern China carries a heavy RR-TB burden, yet research data on the infection status of this population remain scarce. This study aimed to evaluate the incidence of latent tuberculosis infection (LTBI) and active tuberculosis disease (TBD) and their associated factors among HHCs of RR-TB patients in this region through active screening, providing data support for optimizing regional RR-TB prevention and control strategies.

Methods

Using a cross-sectional design, HHCs of RR-TB patients diagnosed at Chengdu Public Health Clinical Medical Center from October 1, 2023, to March 30, 2025, were enrolled. Clinical data were collected via a self-designed questionnaire including gender, age, body mass index (BMI), relationship to index case, living environment, chronic comorbidities, medication history, and TBD-suspicious symptom screening. TBD screening used chest digital radiography (DR) or computed tomography (CT). Clinical data of index cases were extracted from the hospital information system (HIS), covering sputum acid-fast bacillus smear, sputum mycobacterial culture, sputum molecular testing for M. tuberculosis, fluoroquinolone resistance, extent of pulmonary lesions, and cavitation status. TB infection screening employed tuberculin skin test (TST), ESAT6-CFP10 fusion protein skin test (EC), or interferon-γ release assays (IGRA). Infection status was categorized as uninfected, LTBI, or TBD based on screening results, clinical symptoms, and imaging findings. Incidence rates of LTBI and TBD were calculated. Chi-square tests compared clinical characteristics across infection states. Multivariable logistic regression analyzed factors associated with LTBI and TBD (versus uninfected).

Results

264 HHCs from 197 RR-TB index cases were included: 113 males (42.8 %), 151 females (57.2 %), aged 3–78 years (mean 42.4 ± 15.1). Among 209 participants tested with TST: 117 (44.3 %) had induration diameter [0, 5) mm, 17 (6.4 %) [5, 10) mm, 30 (11.4 %) [10, 15) mm, 45 (17.1 %) ≥ 15 mm. Among 46 EC-tested: 29 (11.0 %) had [0, 5) mm, 17 (6.4 %) ≥ 5 mm. Among 9 IGRA-tested: 1 (0.4 %) negative, 8 (3.0 %) positive. After cluster-effect adjustment, LTBI incidence was 31.2 % (95 % confidence interval [CI]: 25.8–38.3), TBD incidence 9.9 % (95 % CI: 6.4–13.6). The proportion of spousal relationships to index cases was higher in LTBI/TBD groups than uninfected (P < 0.05). BMI < 18.5 kg/m² and positive TBD symptom screening were more frequent in TBD than uninfected/LTBI groups (P < 0.05). Pulmonary cavitation in index cases was more common in TBD contacts (P < 0.05). Multivariable analysis showed spousal relationship was an independent associated factor for LTBI (adjusted odds ratio [aOR] = 2.102, 95 % CI = 1.201–3.677; P = 0.009). Factors associated with TBD included: spousal relationship (aOR = 3.949, 95 % CI = 1.553–10.042; P = 0.004), positive TBD symptoms (aOR = 41.988, 95 % CI = 4.270–412.886; P = 0.001), and pulmonary cavitation in index case (aOR = 2.881, 95 % CI = 1.103–7.523; P = 0.031).

Conclusion

High LTBI and TBD rates exist among RR-TB HHCs in this region. Spousal relationship is a risk factor for both LTBI and TBD; positive TBD symptoms and pulmonary cavitation in index cases correlate with TBD. Active screening for RR-TB HHCs and risk-stratified control strategies are recommended to block transmission chains.