Characterization of the Effects of a Novel Probiotic on Salmonella Colonization of a Piglet-Derived Intestinal Microbiota Using Improved Bioreactor

The carriage of Salmonella in pigs is a major concern for the agri-food industry and for global healthcare systems. Humans could develop salmonellosis when consuming contaminated pig products. On the other hand, some Salmonella serotypes could cause disease in swine, leading to economic losses on farms. The purpose of the present study was to characterize the anti-Salmonella activity of a novel Bacillus-based probiotic using a bioreactor containing a piglet-derived intestinal microbiota. Two methods of probiotic administration were tested: a single daily and a continuous dose. Salmonella enumeration was performed using selective agar at T24h, T48h, T72h, T96h and T120h. The DNA was extracted from bioreactor samples to perform microbiome profiling by targeted 16S rRNA gene sequencing on Illumina Miseq. The quantification of short-chain fatty acids (SCFAs) was also assessed at T120h. The probiotic decreased Salmonella counts at T96 for the daily dose and at T120 for the continuous one. Both probiotic doses affected the alpha and beta diversity of the piglet-derived microbiota (p < 0.05). A decrease in acetate concentration and an increase in propionate proportion were observed in the continuous condition. In conclusion, the tested Bacillus-based product showed a potential to modulate microbiota and reduce Salmonella colonization in a piglet-derived intestinal microbiota and could therefore be used in vivo.

A short-term bioreactor assay to assess the effect of essential oils on a microbiota derived from piglet's intestinal content

BACKGROUND

Modulating the microbiota is an emerging way to improve pig health. In-vitro bioreactor systems can be used to reproduce intestinal microbiota to study modulating avenues. In this study, a continuous feeding system to support a microbiota derived from piglet colonic contents, over 72 h, was developed. The microbiota from piglets was collected and used as inoculum. The culture media was derived from an artificial digestion of piglet feed. The microbiota diversity in time, the reproducibility between replicates and the diversity of the bioreactor microbiota compared to the inoculum was assessed. Essential oils were used as a proof of concept to assess the in vitro microbiota modulation. The microbiota diversity was assessed by 16S rRNA amplicon sequencing. Quantitative PCR was also used for total bacteria, lactobacilli and Enterobacteria.

RESULTS

At the start of the assay, the bioreactor microbiota diversity was similar to the inoculum. Time and replication affected the bioreactor microbiota diversity. Between 48 and 72 h, no statistical variation of the microbiota diversity was observable. After a 48 h running period, thymol and carvacrol were added at 200 ppm or 1000 ppm for 24 h. No microbiota modification was observed by sequencing. Quantitative PCR results showed a significant growth of lactobacilli when thymol was used at 1000 ppm, where only a trend was observed with the 16S analysis.

CONCLUSIONS

This study presents a bioreactor assay that can be used as a tool for rapid screening of additives and suggests that the effects of essential oils on the microbiota are subtle, acting against a few bacterial genera.

Effect of the carrier material, drying technology and dissolution media on the viability of Lactobacillus fermentum K73 during simulated gastrointestinal transit

The goal of this study was to determine the effect of the carrier material, drying technology and dissolution media during the passage of L. fermentum K73 through a dynamic in vitro digestion system (IViDiS). The carrier materials were (i) culture medium with growing micro-organisms and (ii) culture medium with maltodextrin : sweet whey [0.6 : 0.4]. The carrier materials were dried by spray-drying and freeze-drying to obtain four types of powders. The dissolution media consisted of water and 1% fat milk. The powders were tested using an in vitro dynamic digestion system (IViDiS). The results showed that powders derived from culture medium had the highest protective effect on the viability of L. fermentum K73 in both dissolution media and that survival increased when the powders were tested in milk. The modified Gompertz model was used to model L. fermentum K73 behaviour during the digestion process. The model showed that cells entrapped in culture medium had the longest lag phase and the slowest inactivation rate when evaluated in milk.

Impact of a yogurt matrix and cell microencapsulation on the survival of Lactobacillus reuteri in three in vitro gastric digestion procedures

The goal of this study was to assess the interaction between microencapsulation and a yogurt food matrix on the survival of Lactobacillus reuteri NCIMB 30242 in four different in vitro systems that simulate a gastric environment. The four systems were: United States Pharmacopeia (USP) solutions, a static two-step (STS) procedure which included simulated food ingredients, a constantly dynamic digestion procedure (IViDiS), as well a multi-step dynamic digestion scheme (S’IViDiS). The pH profiles of the various procedures varied between systems with acidity levels being: USP > STS > IViDiS = S’IVIDiS. Addition of a food matrix increased the pH in all systems except for the USP methodology. Microencapsulation in alginate-based gels was effective in protecting the cells in model solutions when no food ingredients were present. The stability of the probiotic culture in the in vitro gastric environments was enhanced when (1) yoghurt or simulated food ingredient were present in the medium in sufficient quantity, (2) pH was higher. The procedure-comparison data of this study will be helpful in interpreting the literature with respect to viable counts of probiotics obtained from different static or dynamic in vitro gastric systems.

The impact of meals on a probiotic during transit through a model of the human upper gastrointestinal tract

Commercial literature on various probiotic products suggests that they can be taken before meals, during meals or after meals or even without meals. This has led to serious confusion for the industry and the consumer. The objective of our study was to examine the impact of the time of administration with respect to mealtime and the impact of the buffering capacity of the food on the survival of probiotic microbes during gastrointestinal transit. We used an in vitro Digestive System (IViDiS) model of the upper gastrointestinal tract to examine the survival of a commercial multi-strain probiotic, ProtecFlor®. This product, in a capsule form, contains four different microbes: two lactobacilli (Lactobacillus helveticus R0052 and Lactobacillus rhamnosus R0011), Bifidobacterium longum R0175 and Saccharomyces cerevisiae boulardii. Enumeration during and after transit of the stomach and duodenal models showed that survival of all the bacteria in the product was best when given with a meal or 30 minutes before a meal (cooked oatmeal with milk). Probiotics given 30 minutes after the meal did not survive in high numbers. Survival in milk with 1% milk fat and oatmeal-milk gruel were significantly better than apple juice or spring water. S. boulardii was not affected by time of meal or the buffering capacity of the meal. The protein content of the meal was probably not as important for the survival of the bacteria as the fat content. We conclude that ideally, non-enteric coated bacterial probiotic products should be taken with or just prior to a meal containing some fats.

Growth of probiotic bacteria and bifidobacteria in a soy yogurt formulation

Soy beverage and cows' milk yogurts were produced with Steptococcus thermophilus (ATCC 4356) and Lactobacillus delbrueckii subsp. bulgaricus (IM 025). The drop in pH during fermentation was faster in the soy beverage than in cows' milk, but the final pH values were similar. Yogurts were prepared with a yogurt starter in conjunction with either the probiotic bacteria Lactobacillus johnsonii NCC533 (La-1), Lactobacillus rhamnosus ATCC 53103 (GG) or human derived bifidobacteria. The presence of the probiotic bacteria did not affect the growth of the yogurt strains. Approximately 2 log increases in both L. rhamnosus GG and L. johnsonii La-1 were observed when each was added with the yogurt strains in both cows' milk and the soy beverage. Two of the five bifidobacteria strains grew well in the cows' milk and soy beverage during fermentation with the yogurt bacteria. High pressure liquid chromatography (HPLC) analyses showed that the probiotic bacteria and the bifidobacteria were using different sugars to support their growth, depending on whether the bacteria were growing in cows' milk or soy beverage.

Polyphasic characterization of the lactic acid bacteria in kefir

The lactic acid bacteria of kefir were isolated and characterized using phenotypical, biochemical, and genotypical methods. Polyphasic analyses of results permitted the identification of the microflora to the strain level. The genus Lactobacillus was represented by the species Lb. kefir and Lb. kefiranofaciens. Both subspecies of Lactococcus lactis (lactis and cremoris) were isolated. Leuconostoc mesenteroides subsp. cremoris was also found. The kefir studied contained few species of lactic acid bacteria but showed a high number of different strains. We found that the polyphasic analysis approach increases the confidence in strain determination. It helped confirm strain groupings and it showed that it could have an impact on the phylogeny of the strains.

A dynamic model that simulates the human upper gastrointestinal tract for the study of probiotics

A dynamic model of the human upper gastrointestinal (GI) tract was designed to better simulate conditions of ingestion and digestion, by including a food matrix as part of the model design. The dynamic model consisted of two reactors maintained at 37 degrees C, one simulating stomach conditions and the other simulating duodenum conditions. The model was tested by comparing survival of bacteria isolated from humans (Bifidobacterium infantis, Lactobacillus johnsonii, Lactobacillus rhamnosus, and Lactobacillus acidophilus) animals (Bifidobacterium animalis, 2 strains), and fermented dairy products (Bifidobacterium longum, Lactobacillus kefir, Lactobacillus kefirgranum, and Leuconostoc mesenteroides) with their survival as determined by conventional methods. Five strains were not able to survive (>3 log reduction) 15 min in a medium acidified at pH 2.0 using the conventional testing method, but survival was improved significantly for some strains in the dynamic model. Two strains (Bifidobacterium animalis ATCC 25527 and Lactobacillus johnsonii La-1 NCC 533) showed good survival with both methods. The dynamic model was shown to better represent the events during upper GI tract transit than the conventional methods, by incorporation of a food matrix to buffer the gastric acidity and therefore expose bacteria to pH levels found in vivo before, during, and after a meal.