Survival of the probiotic, L. plantarum 299v and its effects on the faecal bacterial flora, with and without gastric acid inhibition

Abstract

Introduction.

Probiotic bacteria have to survive passage through the gastrointestinal tract. In this placebo-controlled double-blind study, the effect of Lactobacillus plantarum 299v on the faecal flora was studied with and without gastric acid inhibition.

Methods.

Thirty-two healthy volunteers were given pantoprazole (40 mg/day) or placebo for 3 weeks from week 2 until week 4. In addition, from week 3 until week 4, L. plantarum 299v in an oatmeal-fermented drink (10⁹ CFU/ml) was given twice daily to both groups. From each healthy volunteer, faecal samples were collected at the end of week 1, 2, 4 and 8 (4 weeks after cessation of L. plantarum 299v and pantoprazole/placebo). Several aerobically and anaerobically growing bacteria were counted and short chain fatty acid concentrations were determined.

Results.

In both the pantoprazole and the placebo group, median lactobacilli counts increased significantly in week 4 compared to week 1 (from log 4.5 to 8.0 CFU/g faeces in pantoprazole and from log 4.2 to 7.7 CFU/g faeces in placebo group) and decreased significantly in week 8 (to log 4.5 CFU/g faeces in pantoprazole and log 4.3 CFU/g faeces in placebo group). These lactobacilli were identified as L. plantarum 299v. No significant differences were observed in all other bacterial counts and short chain fatty acid concentrations.

Conclusions.

The comparable increase of faecal lactobacilli counts in both the pantoprazole and the placebo-treated group demonstrates that L. plantarum 299v survives passage through the gastrointestinal tract irrespective of gastric acidity. The increment of the intra-gastric pH in combination with L. plantarum 299v did not modulate bacterial composition and/or the production of short chain fatty acids.

Introduction

Probiotics as defined by Havenaar et al. [1] are “mono- or mixed cultures of live micro-organisms which, when applied to animal or man, beneficially affect the host by improving the properties of the indigenous microflora”. Probiotics such as lactobacilli have been reported to effect positively, gastrointestinal disorders such as diarrhoea (rotavirus-associated and antibiotic-associated), inflammatory bowel disease, pouchitis, irritable bowel syndrome, colorectal cancer, lactose absorption, Helicobacter pylori infection and constipation and are increasingly used as a treatment modality [2], [3], [4], [5], [6], [7], [8], [9].

For therapeutic purposes, probiotics are restricted by certain selection criteria: probiotics have to be of human origin, have to be safe for the host and genetically stable [8]. Furthermore, it is important that probiotics are able to survive passage through the gastrointestinal tract irrespective of gastric acidity, pancreatic enzymes and bile acids so that they may reach the ileum and colon and can colonize the intestinal mucosa [10]. Furthermore, because of the complexity of the intestinal flora and the high bacterial load, as high as possible numbers of probiotic bacteria reaching the large intestine, being able to be metabolically active seem to be warranted.

The healthy stomach contains relatively small numbers of bacteria (0–10³ colony forming units per ml gastric content) due to the intra-gastric acidity [10], [11]. In healthy volunteers, the median 24-h intra-gastric pH is below 3 in about 80% of time [12]. Most of the ingested bacteria cannot be metabolically active at pH values below 4, and 99.9% of the bacteria are killed at pH less than 4.0 within 30 min [13], [14]. The survival of lactobacilli in acid environments has been tested by in vitro studies: after 4 h, Lactobacillus GG showed no loss of viability in gastric juice within a pH range 3.0–7.0, but there was a rapid loss in viability at pH 1.0 [15]. L. plantarum 299v was able to survive at least 4 h incubation at pH 2.5 in vitro, but no growth or replication could occur [14].

In healthy volunteers, the median 24-h intra-gastric pH has been found to be 1.7 [12]. This may affect survival and/or metabolic activity of probiotic bacteria. An increase in the intra-gastric pH, for instance, by use of gastric acid inhibitors, may theoretically improve the survival of lactobacilli and may increase the metabolic activities of probiotics such as the production of short chain fatty acids.

In this double-blind placebo-controlled study, the effect of L. plantarum 299v on the faecal flora was studied with and without gastric acid inhibition. Special attention was paid to the recovery of L. plantarum 299v in the faeces.