What are microbiome biomarkers and microbiome signatures?

Microbiome biomarkers are microbes that are consistently positively or negatively
associated with a particular condition.

The presence or absence of such a biomarker does not definitively predict if a condition will or
will not develop. However, the predictive power of these microbiome biomarkers becomes
stronger when we combine multiple biomarkers. We call such a group of biomarkers a
microbiome signature.

Microbiome signatures are only valid for specific age groups. The reason for this is that they are
based on scientific studies and datasets that include specific ages. Other age ranges may be
important as well, but without supportive literature, we can not consider them biomarkers with
predictive power. This is why an infant may be “out of range” for a microbiome signature. In the
future, developing research may lead to adjusting the age range for a specific microbiome
signature.

The first microbiome signature we report is between the age range of 3 to 6 months old for
eczema. If the signature is observed in a 3-month old infant, then the infant’s microbiome looks  more like the microbiome of other infants who later develop eczema than infants who do not
develop eczema. In other words, this microbiome signature suggests an increased risk of
developing eczema, but can not be used as a diagnostic tool. Because the early gut microbiome
is uniquely malleable, detection of the eczema microbiome signature may provide a window of
opportunity to shift infant gut microbiome composition and potentially improve health outcomes.