Hazen’s group also found that blood levels of TMAO and L-carnitine could predict heart disease risk, which they learned by collecting blood samples from 2,595 patients and tracking their health for three years.

Molecules proposed as biomarkers for heart disease often look promising in initial studies but fizzle out clinically. “We’ve been down this road so many times before.”

Unfortunately, when laboratory methods rely solely on cultivation of pathogens and traditional phenotypic methods of pathogen characterization, physicians are forced to deduce the presence of BSI based on clinical symptoms, which are often nonspecific. Subsequently, antibiotic therapy is initiated based on clinical and epidemiologic profiles (28) rather than on laboratory evidence. Typically, within 1 to 3 days a microscopic Gram stain category (Gram-positive bacteria, Gram-negative bacteria, or fungi) provides physicians with a general direction for antibiotic therapy. Definitive results that eliminate the need for broad-spectrum therapy and enable de-escalation and the tailoring of treatment to the most effective antibiotic regimen often require more than 3 to 5 days. This gap has been implicated as one reason for high mortality and the emergence of drug-resistant microbes.

“In 15 years, we will all be drinking specific, personalized probiotic cocktails. I suggest that every healthy person freezes a fecal sample now so they will be able to treat themselves in the future.”