Detecting Bacteria in Their Mammalian Hosts Using Metabolism-Targeted [ ¹³ C]CO ₂ Breath Testing

Infectious diseases are a major cause of morbidity and mortality worldwide. With the increasing frequency of antibiotic resistance, efficient and noninvasive diagnostic methods are more important than ever. In this report, we interrogate the use of several intravenously administered, bacteria-specific, 13C-enriched metabolites whose conversion to [13C]CO2 can be detected via a portable and inexpensive method, namely nondispersive infrared (NDIR) spectroscopy. The enriched metabolites [U-13C]maltose, [U-13C]maltotriose, d-[U-13C]mannitol, and l-[U-13C]arabinose were metabolized to [13C]CO2 by several pathogens in vitro, while showing minimal [13C]CO2 production in uninfected mice. We further demonstrated that myositis, bacteremia, pneumonia, and osteomyelitis could be detected in vivo using one or more 13C-enriched metabolites. Additionally, in a model of Escherichia coli myositis, [13C]CO2 production correlated with bacterial burden following ceftriaxone therapy, showing that exhaled [13C]CO2 could be employed to monitor antimicrobial efficacy. Finally, [13C]CO2 production by Staphylococcus aureus clinical isolates treated with [U-13C]maltose was correlated with the performance of its cognate PET tracer [2-18F]maltose, suggesting that [13C]CO2 breath testing could predict the performance of pathogen-targeted positron emission tomography (PET) tracers in vivo. [13C]CO2 breath testing using an expanded metabolite toolbox and on-site detection tools represents a unique and complementary method to identify bacterial infection in clinical practice.