Quantifying the contribution of smear-negative, culture-positive pulmonary tuberculosis to nosocomial transmission

Ya-Jen Yang; Sung-Ching Pan; Meng-Rui Lee; Che-Liang Chung; Chia-Ping Ku; Chi-Yu Liao; Tien-Yu Tsai; Jann-Yuan Wang; Chi-Tai Fang; Yee-Chun Chen

doi:10.1016/j.ajic.2024.02.005

Quantifying the contribution of smear-negative, culture-positive pulmonary tuberculosis to nosocomial transmission

Am J Infect Control. 2024 Feb 15:S0196-6553(24)00076-2. doi: 10.1016/j.ajic.2024.02.005. Online ahead of print.

Authors

Affiliations

¹ Center for Infection Control, National Taiwan University Hospital, Taipei, Taiwan.
² Center for Infection Control, National Taiwan University Hospital, Taipei, Taiwan; Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
³ Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
⁴ Department of Internal Medicine, Yuanlin Christian Hospital, Changhua, Taiwan.
⁵ Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: jywang@ntu.edu.tw.
⁶ Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan; Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan; Population Health Research Center, National Taiwan University, Taipei, Taiwan; Ministry of Health and Welfare and National Taiwan University Infectious Disease Research and Education Center, Taipei, Taiwan. Electronic address: fangct@ntu.edu.tw.

PMID: 38365178
DOI: 10.1016/j.ajic.2024.02.005

Abstract

Background: Despite current guidelines for tuberculosis (TB) control in health care settings, which focused on smear-positive cases, prevention of nosocomial TB transmission continues to be a challenge. Here, we report the results of the first hospital-wide prospective study applying interferon-gamma release assay to investigate the role of smear-negative, culture-positive index cases in nosocomial TB transmission.

Methods: We prospectively identified cases of culture-confirmed smear-negative pulmonary TB receiving aerosol-generating procedures (AGPs) and cases of culture-confirmed smear-positive pulmonary TB admitted at a medical center. Nosocomial transmission was evaluated by screening their close contacts for latent TB infection (LTBI) using an interferon-gamma release assay.

Results: A total of 93 smear-negative index receiving AGP and 122 smear-positive index were enrolled. Among them, 13 (14.0%) and 43 (35.2%) index cases, respectively, had secondary cases of LTBI (P < .001). Sputum smear negativity (adjusted odds ratio: 0.20 [0.08-0.48]) and AGP (sputum suction; adjusted odds ratio: 3.48 [1.34-9.05]) are independent factors of transmission. A similar proportion in the close contacts of the 2 index groups had LTBI (17 [15.3%] and 63 [16.0%], respectively), and the former index group contributed to 21.3% of the nosocomial transmission.

Conclusions: Smear-negative, culture-positive index cases receiving AGPs could be as infectious as smear-positive index cases. Hospital TB control policy should also focus on the former group.

Keywords: Acid-fast smear; Aerosol-generating procedure; Contact investigation; Interferon-gamma releasing assay (IGRA); Latent tuberculosis infection.