Analysis of Volatile Substances in Breath of Pneumonia Patients Confirms Fungal Infection Diagnosis

Analysis of volatile substances in the breath of patients with respiratory infections has been proposed as a novel, noninvasive, pathogen-specific approach to identifying the precise microbial cause of pneumonia.

Investigators at Brigham and Women's Hospital (Boston, MA, USA) were particularly interested in the fungus Aspergillus fumigatus, which causes an often fatal type of pneumonia in patients with compromised immune systems.

The investigators first identified unique volatile substances produce by A. fumigatus growing in Petri dishes and then used thermal desorption-gas chromatography/mass spectrometry to attempt to detect these substances in the breath of pneumonia patients.

Among the distinctive substances produced by cultures of A. fumigatus that could be used to distinguish it from other pathogenic aspergilli were the monoterpenes camphene, alpha- and beta-pinene, and limonene and the sesquiterpene compounds alpha- and beta-trans-bergamotene.

The investigators analyzed breath samples that had been collected from 2011 to 2013 from 64 patients with suspected invasive fungal pneumonia. Results revealed that of the 64 patients who had been diagnosed with suspected invasive fungal pneumonia based on host risk factors, clinical symptoms, and radiological findings, 34 were diagnosed with invasive aspergillosis, whereas 30 were ultimately diagnosed with other causes of pneumonia, including other invasive fungal infection. Detection of alpha-trans-bergamotene, beta-trans-bergamotene, a beta-vatirenene-like sesquiterpene, or trans-geranylacetone identified invasive aspergillosis patients with 94% sensitivity and 93% specificity.

"Identification of the underlying microbial etiology remains elusive in most patients with pneumonia, even with invasive diagnostic measures," said first author Dr. Sophia Koo, assistant professor of medicine at Brigham and Women's Hospital. "Our findings provide proof-of-concept that we can harness detection of species-specific metabolites to identify the precise microbial cause of pneumonia, which may guide appropriate treatment of these infections. We can likely also use this volatile metabolite profiling approach to identify other, more common causes of pneumonia."

The proof-of-concept study was published in the October 22, 2014, online edition of the journal Clinical Infectious Diseases.

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