Viability assessment of the probiotic spore former B. Subtilis: An investigation into the effect of in-vitro pig gastric condiitons

Bowe, Catherine (2015) Viability assessment of the probiotic spore former B. Subtilis: An investigation into the effect of in-vitro pig gastric condiitons. Doctoral thesis, Northumbria University.

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Abstract

Probiotics are bacteria which have the capacity to exert a beneficial effect upon the host when consumed in sufficient numbers. However, in order for these bacteria to colonise the gut, they need to survive the harsh conditions of the upper gastrointestinal tract (GIT). In this project, the probiotic spore former Bacillus subtilis has been investigated upon exposure to simulated pig gastric conditions. The main aim of this work was to elucidate what phenomena influence the perceived decline in viable count observed in gastric conditions by exploring the impact of acidified medium on the physiological state and viability of spores. It was anticipated that the main cause of spore death would either be a germination-induced death, or a direct sporicidal effect.

The findings of this work highlight the need to find better methods to assess bacterial numbers, as current methods may give misleading data into probiotic survival in the host. The advantage of using a method such as FCM is also highlighted, given its ability to assess sub-populations of bacteria, rather than being limited to assessing culturability. Furthermore, the need for precise dosing instructions with regards to probiotics should also be considered.

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