[2] When grown on general anaerobic medium, B. longum forms white, glossy colonies with a convex shape.

[3] This number gradually drops to 3% in an adult's gastrointestinal tract as other enteric bacteria such as Bacteroides and Eubacterium begin to dominate.

[12] B. longum is considered to be a scavenger, possessing multiple catabolic pathways to use a large variety of nutrients to increase its competitiveness among the gut microbiota.

[3] This is necessary as mono- and disaccharides have usually been consumed by the time they reach the lower gastrointestinal tract where B. longum resides.

These are primarily cases in preterm infants that are undergoing probiotic treatment,[16][17][18] although there are also reports of infection in adults.

[19][20][21] Infection in preterm infants manifests as bacteremia or necrotizing enterocolitis,[22] while in adults there have been reports of sepsis and peritonitis.

The use of B. longum was shown to shorten the duration and minimize the severity of symptoms associated with the common cold with a similar effect to that of neuraminidase inhibitors for influenza.

[24] Large scale clinical trials have shown that the strain is effective in controlling the symptoms of IBS including bloating, diarrhoea, abdominal pain and discomfort.