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Updated: Dec 20, 2025
An Automated Culture System for Use in Preclinical Testing of Host-Directed Therapies for Tuberculosis
Published on: August 16, 2021
Prompt recognition of infectious pulmonary tuberculosis is critical to achieving elimination goals: a retrospective
Courtney Heffernan1, James Barrie2, Alexander Doroshenko3
1Department of Medicine; Division of Pulmonary Medicine, University of Alberta, Edmonton, Alberta, Canada.
Introduction:
All pulmonary tuberculosis (PTB) cases are presumed to be infectious to some degree. This spectrum of infectiousness is independently described by both the acid-fast bacilli smear and radiographic findings. Smear-positive patients with chest radiographic findings that are typical for adult-type PTB are believed to be most infectious.
Hypothesis:
Characterisation of the presumed most infectious PTB case is possible by reference to readily available clinical features and laboratory results.
Methods:
Retrospective cohort study of adult, culture-positive PTB cases (151 smear-positive; 162 smear-negative) diagnosed between 1 January 2013 and 30 April 2017 in Canada. We describe cases according to demographic, clinical and laboratory features. We use multivariable multinomial logistic regression to estimate the relative risk ratio (RRR) with 95% CI of features associated with an outcome of smear-positive PTB, characterised by 'typical' chest radiograph findings.
Results:
Being Canadian-born, symptomatic, having a subacute duration of symptoms and broad-spectrum antibiotic prescriptions were all more commonly associated with smear-positive than smear-negative disease (36% vs 20%; 95% vs 63%; 88% vs 54%; and 59% vs 28%, respectively). After combining smear status and radiographic features, we show that smear-positive patients with typical chest radiographs were younger, had a longer duration of symptoms (RRR 2.41; 95% CI 1.01 to 5.74 and 2.93; 95% CI 1.20 to 7.11, respectively) and were less likely to be foreign-born, or have a moderate to high-risk factor for reactivation (RRR 0.40; 95% CI 0.17 to 0.92 and 0.18; 95% CI 0.04 to 0.71, respectively) compared with smear-negative patients with atypical chest radiograph findings.
Conclusion:
A clear picture of the presumed most infectious PTB case emerges from available historical and laboratory information; vigilance for this presentation by front-line providers will support elimination strategies aimed at reducing transmission.
Insights
Identifying the most infectious pulmonary tuberculosis (PTB) cases is possible using clinical and lab data. Smear-positive PTB patients with typical chest X-rays are younger and have longer symptoms, aiding transmission reduction efforts.
Area of Science:
- Infectious Diseases
- Public Health
- Radiology
Background:
- Pulmonary tuberculosis (PTB) infectiousness varies, with smear-positive cases exhibiting typical radiographic findings considered most infectious.
- Characterizing the most infectious PTB cases relies on accessible clinical and laboratory data.
Purpose of the Study:
- To identify clinical and laboratory features associated with the most infectious PTB cases, defined as smear-positive with typical chest radiographs.
- To inform strategies for reducing PTB transmission by understanding transmission dynamics.
Main Methods:
- Retrospective cohort study of adult, culture-positive PTB cases in Canada (2013-2017).
- Analysis of demographic, clinical, and laboratory features.
- Multivariable multinomial logistic regression to determine relative risk ratios (RRR) for smear-positive PTB with typical radiographic findings.
Main Results:
- Smear-positive PTB with typical radiographs was associated with being Canadian-born, symptomatic, having subacute symptoms, and prior broad-spectrum antibiotic use.
- These patients were younger and had longer symptom durations (RRR 2.41-2.93) compared to smear-negative cases with atypical radiographs.
- They were less likely to be foreign-born or have reactivation risk factors (RRR 0.18-0.40).
Conclusions:
- A profile of the most infectious PTB case can be established using historical and laboratory data.
- Vigilance for this profile by healthcare providers is crucial for PTB elimination strategies and reducing transmission.
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