Stability and viability of probiotic bacteria

The aim of this study was to determine if commercially available strains of probiotic bacteria belonging to the species Ent. faecalis and E. coli were able to survive passage through the human stomach and colonise the gastrointestinal tract (GIT). Survival of bacteria following exposure to gastric pH levels was assessed using a dynamic in vitro model resembling conditions in the stomach as well as the SHIME® model more closely mimicking the upper GIT environment (stomach and small intestine) during fed conditions.

Viability of both Ent. faecalis DSM 16431 and E. coli DSM 17257 decreased during acid exposure. However, subsequent exposure to simulated small intestine conditions resulted in no further decrease. A human volunteer took a single dose of probiotic Ent. faecalis, after which live bacteria were determined for 6 days in faeces by means of targeted cultivation and identification of colonies using species- and strain-specific PCR primers. Detection of the strain’s DNA by PCR in stool samples was positive for 4 days. This duration of colonisation was much shorter compared to previously determined human colonisation by E. coli DSM 17257.

In conclusion, probiotic E. coli and Ent. faecalis are susceptible to gastric pH, which reduces their viability with several logs. However, sufficient numbers survive to colonise the gut, so that the bacteria are detected in the stool for several days (Ent. faecalis) and multiple weeks (E. coli) following a single dose.

Publication language: English