Persistence of lactic acid bacteria from fermented foods in the oral cavity of rats, potential links with oral microbiota, salivary composition and taste perception

Les aliments fermentés constituent une part importante de notre alimentation. Certains d’entre eux ont montré un effet bénéfique au niveau intestinal pouvant être lié à la persistance de certaines de leurs bactéries, principalement des bactéries lactiques. La persistance de ces bactéries lactiques dans la cavité orale suite à leur consommation a été peu étudiée. Pour cette raison, le premier objectif de cette thèse était de déterminer si les bactéries lactiques présentes dans les aliments fermentés persistent dans la cavité orale. Pour répondre à cette question, un modèle de fromage contenant 3 espèces bactériennes (Streptococcus thermophilus, Lactococcus lactis, et Lacticaseibacillus paracasei) communément présentes dans les aliments fermentés a été développé. Les effets de la consommation de ce fromage ont été étudiés sur un modèle rat. Pour cela, plusieurs groupes de rats ont été soumis à différents protocoles, en plus de leur régime standard. Ces protocoles consistaient à administrer quotidiennement un morceau de fromage supplémentaire soit ionisé (fromage avec des bactéries lactiques mortes), soit non ionisé (avec des bactéries lactiques vivantes). Suite à ce régime, des échantillons de salive et de fèces ont été prélevés sur chaque rat. Sur l'ensemble des rats ayant reçu le fromage non-ionisé, les résultats ont montré qu’un tiers présentait des bactéries lactiques dans leur cavité buccale de manière transitoire. Ces résultats ont mis en évidence une importante variabilité interindividuelle dans la persistance des bactéries lactiques du fromage. Afin de déterminer quels sont les facteurs à l’origine de cette variabilité, le deuxième objectif de la thèse était de définir l'impact de de facteurs endogènes comme le microbiote oral et le protéome salivaire sur la persistance des bactéries du fromage dans la cavité orale. Ces résultats ont montré que le microbiote oral endogène était modifié suite à la consommation de fromage, mais sans corrélation avec la persistance des bactéries lactiques. De plus, l’analyse du protéome salivaire lors du pré-régime suggère que la persistance des bactéries lactiques exogènes pourrait être liée à la réponse au stress oxydant. Finalement, le troisième objectif était de répondre à la problématique suivante: Est-ce que des individus présentant des sensibilités gustatives différentes peuvent-ils réagir différemment à la consommation d'un même aliment ? Les résultats montrent que le microbiote intestinal est différent chez des animaux de sensibilité gustative différente, alors que leur microbiote oral est similaire. Ils montrent aussi que la persistance des bactéries lactiques diffère en fonction de la sensibilité gustative aussi bien au niveau oral, qu’au niveau intestinal.Cette thèse montre pour la première fois les relations entre la consommation de bactéries lactiques et l’environnement oral (salive et microbiote) ainsi que les relations avec la sensibilité gustative.Fermented foods are an important part of our diet. Some of them have shown a beneficial effect at the intestinal level, which may be linked to the persistence of some of their bacteria, mainly lactic acid bacteria (LAB). The persistence of these LAB in the oral cavity after their consumption has been little studied. For this reason, the first objective of this thesis was to determine whether LAB present in fermented food persists in the oral cavity. To answer this question, a cheese model containing 3 bacterial species (Streptococcus thermophilus, Lactococcus lactis, and Lacticaseibacillus paracasei) commonly present in fermented foods was developed. The effects of consuming this cheese were studied in a rat model. For this purpose, several groups of rats were subjected to different protocols, in addition to their standard diet. The protocols involved giving an extra piece of cheese daily, which could either be ionised (cheese containing dead LAB) or non-ionised (containing live LAB). Following the diet, saliva and feces samples were collected from each rat. The results showed that approximately one-third of the rats that ingested non-ionized cheese present their LAB transiently in their oral cavity. These data showed a significant inter-individual variability in the persistence of LAB. To determine which factors were responsible for this variability, the second objective of the thesis was to define the impact of endogenous factors such as the oral microbiota and the salivary proteome on the persistence of cheese bacteria in the oral cavity. These results showed that the endogenous oral microbiota was modified after cheese consumption, but without correlation with the persistence of LAB. Furthermore, the analysis of the salivary proteome during the pre-diet suggests that the persistence of exogenous LAB may be related to the oxidative stress response. Finally, the third objective was to answer the following question: Can individuals with different taste sensitivities react differently to the consumption of the same food? The results show that the gut microbiota is different in animals with different taste sensitivities, while their oral microbiota is similar. They also show that the persistence of LAB differs according to taste sensitivity at both, oral and intestinal levels.This thesis shows for the first time the relationship between the consumption of LAB and the oral environment (saliva and microbiota), as well as, the relationship with taste sensitivity

Chapter 17 - Relationship between fermented food, oral microbiota, and taste perception

International audienceThe oral cavity hosts an important amount of microorganisms characterized by an important diversity. This diversity is partly due to the presence of various ecological niches in the oral cavity with different physicochemical and biochemical properties. The totality of these microorganisms constitutes the oral microbiota. The oral microbiota has been studied for years, especially for its implication in various oral pathologies including dental caries and periodontal disease. However, its implication in other physiological functions has started to be studied recently. Among them, we can mention taste perception. The implication of the oral microbiota in this perception appears highly credible since the surface of the tongue, which is at the interface between the oral cavity and the taste receptors, is covered by a rich and diverse microbial biofilm. Similarly, saliva, which is the fluid where sapid compounds are diluted before reaching taste receptors, is also a medium where planktonic bacteria are strongly represented. Besides the potential role of this oral microbiota, the implication of food microbiota and particularly fermented foods microbiota to taste perception is poorly known although the consumption of these products leads to the introduction of billions of exogenous microorganisms in the oral cavity. The aim of this chapter is then, in the first part, to give an overview of the characteristics of the oral microbiota. A second part will focus on the fermented food microbiota and the products of their metabolism having a potential impact on taste perception. Finally, the last part will review the potential implications of the oral microbiota in taste perception

Oral microbiota modulation by fermented food; impact of salivary proteome

International audienc

Impact of consumption of a cheese containing three Lactic Acid Bacteria on the oral microbiota of rats

National audienceFermented food consumption is recommended for health and environmental purposes. While it is known to impact gut microbiota, further investigation is needed to establish connections with the oral microbiota. For this purpose, we investigated the effect of daily consumption of a model cheese containing three Lactic Acid Bacteria (LAB) species on the oral microbiota of rats following a 3-weeks diet. Cheese consumption transiently modifies the oral microbiota and leads to a transient persistence of LAB in the oral cavity of 1/3 of the animals. While we found no differences in salivary microbiota composition between rats with and without LAB persistence before cheese exposure, salivary proteome was found different in these two groups. Particularly, an overrepresentation of salivary proteins involved in the response to oxidative stress was observed in animals without LAB persistence, which may partly explain the variability in terms of bacteria persistence. These findings highlight the significance of fermented foods in shaping the diversity of the oral microbiota. Additionally, they suggest that variations in the salivary proteome among individuals may influence the permissiveness of the oral microbiota towards exogenous microorganisms

Oral microbiota modulation by fermented food; impact of salivary proteome

International audienc

Fermented food consumption modulates the oral microbiota

International audienceFermented food consumption is recommended for health and environmental purposes. While it is known to impact gut microbiota, further investigation is needed to establish connections with the oral microbiota. For this purpose, we investigated the effect of daily consumption of a model cheese containing 3 Lactic Acid Bacteria (LAB) species on the oral microbiota of rats following a 3-week diet. Cheese consumption transiently modifies the oral microbiota and leads to a transient persistence of LAB in the oral cavity of 1/3 of the animals. The origin of this variability was partly explained by an overrepresentation of salivary proteins involved in the response to oxidative stress in animals without LAB persistence. These findings highlight the significance of fermented foods in shaping the diversity of the oral microbiota. Additionally, they suggest that variations in the salivary proteome among individuals may influence the permissiveness of the oral microbiota towards exogenous microorganisms

Fermented food consumption modulates the oral microbiota

International audienceFermented food consumption is recommended for health and environmental purposes. While it is known to impact gut microbiota, further investigation is needed to establish connections with the oral microbiota. For this purpose, we investigated the effect of daily consumption of a model cheese containing 3 Lactic Acid Bacteria (LAB) species on the oral microbiota of rats following a 3-week diet. Cheese consumption transiently modifies the oral microbiota and leads to a transient persistence of LAB in the oral cavity of 1/3 of the animals. The origin of this variability was partly explained by an overrepresentation of salivary proteins involved in the response to oxidative stress in animals without LAB persistence. These findings highlight the significance of fermented foods in shaping the diversity of the oral microbiota. Additionally, they suggest that variations in the salivary proteome among individuals may influence the permissiveness of the oral microbiota towards exogenous microorganisms

[Thu-P1-055] Influence of fermented food consumption on taste and oral microbiota of rats

International audienceOral microbiota varies throughout the individual’s life. These changes are due to several factors (environmental, physiological, lifestyle...) that shape its diversity and composition. However, little is known about the physiological impact of this persistence. Taste perception is one of the possible targeted functions. Indeed, our team has recently established relationships between oral microbiota and taste sensitivity in humans. The objective of this work was to see if fermented food bacteria were able to persist in the oral cavity and consequently influence the oral microbiota and the taste by using a rodent experimental design: two groups of rats (n=27/group) were fed for 3 weeks with experimental cheeses containing live or dead bacteria. Rat saliva was collected weekly for bacterial composition analysis (qPCR and 16S rRNA sequencing). Taste sensitivity was evaluated using the 2 bottles test method with 4 decreasing sucrose concentrations. First results, we found that 1/3 of the rats who consumed cheese with alive bacteria have these bacteria transiently in their oral cavity. However, their sucrose taste sensitivity was not significantly affected by comparing with rats without cheese bacteria persistence. This work shows that fermented food can modulate temporarily the composition of rat oral microbiota without leading to changes in the sucrose perception. However, this work needs to be reinforced by performing a longer exposure and by investigating the sensitivity to other tastes

Persistence of fermented food bacteria in the oral cavity of rats after one week of consumption

International audienceFermented foods constitute a wide source of exogenous lactic acid bacteria (LAB) which could modify the endogenous microbiota of the consumer's digestive tract. This assumption depends on the ability of LAB to persist, at least transiently, in the oral cavity. The aim of this study was to evaluate the persistence of 3 LAB species, Streptococcus thermophilus, Lactococcus lactis, and Lacticaseibacillus paracasei in the oral cavity of rats by feeding them with a daily portion of model cheese containing the three bacteria for one week. Saliva samples were collected 16 h and one week after the last daily cheese intake. Their cheese bacteria contents were quantified by qPCR. When 16 h after cheese consumption, cheese bacteria were detected in the oral cavity of about ⅓ of the rats ranging from 10−3% to 10−1% of the total bacteria. One week after the last cheese intake, 1/8 LAB remains in the oral cavity. This study is a proof of concept showing that LAB can remain in the oral cavity several days after fermented food consumption with variability depending on individuals

Influence of fermented food consumption on oral microbiota and taste perception

International audienc