Volatile Molecules from CF Patients May Help Identify Bacterial Infections, Researchers Find

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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volatile molecules in BAL samples

Volatile molecules present in bronchoalveolar lavage (BAL) samples from cystic fibrosis (CF) patients may help identify those infected with Pseudomonas aeruginosa and Staphylococcus aureus.

The study, “Volatile molecules from bronchoalveolar lavage fluid can ‘rule-in’ Pseudomonas aeruginosa and ‘rule-out’ Staphylococcus aureus infections in cystic fibrosis patients,” appeared in the journal Scientific Reports.

Pseudomonas aeruginosa is one of the most common bacterial species found in the airways of CF adults, and Staphylococcus aureus is among the most common bacteria found in children with cystic fibrosis..

“Clinical best practice, as defined by the CF Foundation Pulmonary Guidelines, is to routinely surveil CF patients for new or recurring P. aeruginosa infections and initiate antibiotic eradication therapy at first detection, in an effort to prevent chronic infection and preserve lung function,” researchers wrote.

Being able to detect S. aureus is also important because a variant, called methicillin-resistant S. aureus (MRSA), is linked to worse survival of CF patients.

Researchers from analyzed BAL samples from CF patients collected from 13 centers in the U.S. through the Cystic Fibrosis Foundation Therapeutics (CFFT) biorepository. The 154 samples they collected were analyzed for volatile molecules using a method called two-dimensional gas chromatography time-of-flight mass spectrometry.

“The measurement of volatile molecules from respiratory specimens, including BAL fluid, sputum and breath has been proposed as a minimally-invasive approach for differentiating P. aeruginosa-positive from P. aeruginosa-negative CF patients,” the researchers wrote.

They identified nine volatile molecules that could differentiate P. aeruginosa-positive from negative samples with the Area Under a ROC Curve – called the AUROC parameter – of 0.86. AUROC is used to measure the accuracy of a test to distinguish two groups, where the area under the ROC curve represents accuracy. A value of 1 represents the best value of accuracy, a value close to 1 indicates high predictive accuracy, while a value of 0.5 represents poor accuracy.

Eight volatile molecules were found that could distinguish S. aureus-positive from S. aureus-negative samples. In this case the AUROC value was 0.88.

“We conclude that volatile molecules from BAL fluid can provide discriminatory power for ruling in P. aeruginosa and ruling out S. aureus and plan to extend this work to exhaled breath in CF patients,” investigators wrote.

Given the fact that collecting BAL samples is an invasive and expensive method, as well as difficult to perform in a clinical setting, researchers propose that “the biomarkers in this study can now serve as a basis for designing well-powered breath studies in the CF patient population, an avenue we are currently exploring.”