by Maja Rudolphson,Karolinska Institutet

Credit: Unsplash/CC0 Public Domain

Researchers at Karolinska Institutet, in collaboration with colleagues in South Africa, have investigated whether tuberculosis can be traced in exhaled air. The results,publishedinOpen Forum Infectious Diseases, show that a new method may help identify people with infectious tuberculosis directly in primary care.

Tuberculosis is anairborne diseasethat is often diagnosed by analyzing sputum—mucus coughed up from the lungs. However, not all patients are able to produce sputum, which makes detection more difficult. In a new study, researchers tested whether DNA from thetuberculosisbacterium could be detected in exhaled air—known as aerosols—in people seeking care for respiratory symptoms.

The study was conducted atprimary careclinics in South Africa and included 137 adult participants with tuberculosis. The researchers used a new device, TB Hotspot detectOR (THOR), which collects aerosols using electrostatic sampling. The samples were analyzed using the same technique as for sputum, Xpert MTB/RIF Ultra.

The results show that the method was able to detect tuberculosis DNA in exhaled air in 47% of those who had a positive sputum test. Among those with high levels of bacteria in sputum, the sensitivity was slightly higher at 57%. At the same time, the specificity—the ability to correctly identify those without the disease—was 77%.

"It is promising that we can detect infectious tuberculosis directly in the air, especially in settings where sputum samples are difficult to obtain," says Jay Achar, researcher in the Department of Global Public Health at Karolinska Institutet.

The study also found that certain factors increased the likelihood of detecting tuberculosis DNA in aerosols. This was particularly true for men with high bacterial levels in sputum. Conversely, people with fever were slightly less likely to test positive in air samples.

"This is a first step towards understanding how tuberculosis is transmitted and how we can identify infectious individuals earlier," says Achar.

The researchers also noted that DNA from thetuberculosis bacteriumwas found in 30% of environmental samples taken in the clinic setting, despite thorough cleaning. This suggests that the method is sensitive but also highlights potential risks of transmission in health care environments.

More information: Jay Achar et al, Detection of aerosolized Mycobacterium tuberculosis DNA from adults being investigated for pulmonary tuberculosis using an electrostatic sampler in a South African primary care setting, Open Forum Infectious Diseases (2025). DOI: 10.1093/ofid/ofaf593

Provided by Karolinska Institutet