Novel Breath Test Differentiates Bacterial from Viral Infections

Researchers have developed a novel breath-based test method designed to non-invasively detect bacterial infections and differentiate them from viral infections or non-infectious inflammation. This innovative approach utilizes specific molecules metabolized solely by infecting bacteria, resulting in the production of a traceable gas detected in the breath. Initial proof-of-concept experiments conducted in animal models show significant potential for a rapid and accessible diagnostic tool.

The approach utilizes specific molecules metabolized solely by infecting bacteria, which results in the production of a traceable gas detected in the breath.

Method Development and Mechanism

Developed by a team including David Wilson, Kiel Neumann, and Marina López-Álvarez, the method involves administering sugar and sugar alcohols, specifically a version of mannitol, tagged with the carbon-13 isotope. When these labeled compounds are introduced into the body, infecting bacteria metabolize them, producing carbon-13 labeled carbon dioxide as a byproduct. Human cells and the body's natural gut bacteria largely disregard these specific tagged molecules, ensuring that the detected carbon-13 is indicative of bacterial activity.

The labeled carbon dioxide is then detected rapidly in the exhaled breath using nondispersive infrared (NDIR) spectroscopy. This detection instrument is described as inexpensive and portable.

Experimental Findings: Rapid Detection in Animal Models

Experiments were conducted using mice infected with various bacterial conditions, including pneumonia, bloodstream infections (bacteremia), muscle infections (myositis), and bone infections (osteomyelitis). Following intravenous injections of the tagged compounds, elevated levels of labeled carbon dioxide in the animals' breath typically appeared within 10 minutes of administration and sampling. In contrast, healthy mice exhibited minimal to no carbon-13 in their breath.

The research included common pathogens such as Staphylococcus aureus, Streptococcus pneumoniae, and Escherichia coli. It also covered Salmonella enterica, a pathogen particularly relevant for immunocompromised individuals where distinguishing between infection and inflammation can be challenging.

Potential Applications: Faster Diagnosis and Treatment Monitoring

Beyond diagnosing the presence of an infection, the method indicated potential for monitoring the effectiveness of treatment. In an E. coli infection model, the amount of labeled carbon dioxide in the breath decreased as bacterial levels were reduced during antibiotic treatment.

The developers suggest that the test could serve as a quick screening tool to ascertain the presence of a bacterial infection. Current diagnostic methods, such as laboratory cultures, often require several days, whereas this breath test could deliver much faster results. The sugar and sugar alcohols used in the test are considered safe for human consumption.

Current diagnostic methods, such as laboratory cultures, often require several days, whereas this breath test could deliver faster results.

The approach aims to contribute to reducing unnecessary antibiotic prescriptions by providing a rapid, affordable, and accessible diagnostic tool.

Research Institutions and Future Outlook

The study was conducted by researchers from St. Jude Children's Research Hospital and the University of California, San Francisco. It was published in ACS Central Science. Funding for the work was provided by the National Institutes of Health and the Cystic Fibrosis Foundation. A U.S. patent related to this research has been filed. This study is considered a foundational step toward further clinical studies to evaluate its broader applicability.