A Breath of Air Could Help Diagnose Gut Microbiome Disruptions

In the depths of the human colon, gut microbes help keep the body healthy by aiding digestion and producing vital metabolites. Disruptions to this bustling microbial community are associated with diseases including asthma and serious infections in preterm infants. However, quickly identifying the gut microbiome changes that can lead to these conditions in a hospital is not feasible with current methods.

“One of the key barriers to integrating our knowledge of the microbiome into clinical care is the time it takes to analyze the data on the microbiome,” said Ariel Hernandez-Leyva, an MD/PhD student in gut microbiome researcher Andrew Kau’s group at Washington University School of Medicine (WashU Medicine), in a statement.

Instead, he and his colleagues at WashU Medicine and infectious disease researcher Audrey Odom John's group at Children’s Hospital of Philadelphia turned to a sample that’s much easier to access and analyze: breath.

In a new study published in Cell Metabolism, the researchers discovered that volatile organic compounds (VOCs) in breath samples correlate with gut microbiome changes in both humans and mice.¹ They also showed that VOCs in breath samples from children with asthma could help predict the level of a gut bacterial species associated with the condition. The findings point to the breath as a potential way to quickly diagnose conditions associated with the gut microbiome.

As gut microbes metabolize food and other compounds in the gut, they release VOCs. To find out if VOCs in the breath could help identify gut microbes, the team took breath and stool samples from 27 healthy children. They performed metagenomic sequencing on the stool samples and gas chromatography-mass spectrometry on the breath samples. They found that the VOCs in the children’s breath corresponded to the metabolites produced by the gut bacteria. The researchers performed a similar analysis in mice and found that the animals’ breath “volatilome” also served as a good proxy for the gut microbiome.

Hernandez-Leyva, Kau, and their team then asked if they could use breath to identify changes in the gut microbiome associated with disease. As a proof-of-concept, they evaluated children with asthma; this condition is associated with high levels of the bacterial species Eubacterium siraeum in the gut.² The team compared the breath samples of the same group of healthy children as in their earlier experiment with breath samples from 14 children with asthma. Using this data, the researchers built a model with the four VOCs that best differentiated the healthy and asthma samples and found that the model predicted the abundance of E. siraeum in the kids’ guts.

“Rapid assessment of the gut microbiome’s health could significantly enhance clinical care, especially for young children,” said Kau. “Early detection could lead to prompt interventions for conditions like allergies and serious bacterial infections in preterm infants. This study lays the groundwork for developing such crucial diagnostic tools.”