A study conducted by a team of researchers from the Division of Internal Medicine, University Hospital Basel, Basel, Switzerland is exploring whether or not exhaled breath could be a promising alternative to blood for the therapeutic monitoring of antibiotics.

Therapeutic drug monitoring (TDM) is often used to monitor antibiotic concentrations in patients with severe infections and in patients in intensive care units to ensure they are receiving the appropriate dosage of antibiotics based on their needs — for instance, patients might metabolize drugs differently and consequently not respond to conventional doses of antibiotics, perhaps requiring higher or lower doses.

Traditionally, TDM is performed using blood collection methods that tend to be invasive as well as time- and resource-consuming, often taking several hours and even days to get results.

As such, the team is examining whether exhaled breath might be a painless and suitable alternative, citing that the process is non-invasive and that breath when combined with real-time analyses, potentially offering results in roughly 10 minutes in some cases.

To test this approach, the team conducted a proof-of-concept study with 10 patients (median age 63 years, 54.5% female) who had received intravenous antibiotic treatment in 2022 or 2023.

The patients were being treated for: respiratory infections (n=3), intravascular infections (n=3), abdominal infections (n=2), urinary tract infection (n=1) or skin and soft tissue infection (n=1) with meropenem (n=3), piperacillin/tazobactam (n=3), cefazolin (n=2), flucloxacillin (n=1) or ciprofloxacin (n=1).

To analyze samples of exhaled breath for exogeneous and endogenous metabolites — which are, respectively, the breakdown products of the antibiotic and breakdown products from the body affected by the antibiotic — the team employed mass spectrometry.

For the antibiotics meropenem, cefazolin, flucloxacillin and ciprofloxacin, it was possible to detect differences in the levels of specific metabolites while with the antibiotic piperacillin/tazobactam there was no clear, detectable signal.

The researchers hope that by being able to measure levels of these metabolites, it will eventually be possible to monitor antibiotic concentrations without taking blood samples.

The reseachers explained: “We were able to detect antibiotic-specific metabolites in exhaled breath in patients treated with antibiotics in four out of five antibiotics investigated.

“We aim to confirm these very promising results in a larger cohort of patients, as well as look at how they relate to blood plasma concentrations of antibiotics and patient outcomes.”

To contact the author of this article, email mdonlon@globalspec.com