Survival and retention of the probiotic Lactobacillus casei LAFTI® L26 in the gastrointestinal tract of the mouse

Aims: This study aimed to develop methods for the detection of the probiotic Lactobacillus casei LAFTI (R) L26 (L26) from mouse faeces, and to determine the survival and retention time of L26 in the mouse gastrointestinal tract. Methods and Results: A selective medium, de Man Rogosa Sharpe (MRS) + bromocresol green + vancomycin (MGV), was designed for the isolation and enumeration of L26 from faecal samples of mice. PCR primers were designed to confirm the identity of L26-like colonies on MGV. These primers did not produce PCR products from related organisms that grew on MGV. Following the administration of L26 to BALB/c mice, faecal samples were collected and analysed using the designed methods. Survival studies showed viable L26 cells to be present in the faeces of mice for > 48 h. Conclusions: Our results suggest that L26 is able to survive and be retained within the digestive tract of mice for at least 48 h following oral administration. Significance and Impact on the Study: MGV allows effective recovery of L26 from the background microbiota, including lactobacilli of mice. PCR was used to confirm that L26-like colonies were correctly identified as L26. Given the long retention time of L26 in the gastrointestinal tract of mice, it would appear that this probiotic strain may survive in the human gastrointestinal tract.