Physical properties of lactic acid bacteria influence the level of protection against influenza infection in mice.

Takumi Watanabe,Isao Takahashi,Kyoko Hayashi,Makoto Ohwaki,Tatsuhiko Kan,Toshio Kawahara,Wenke Feng

doi:10.1371/journal.pone.0251784

Takumi Watanabe, Isao Takahashi + Show 5 more

Open Access

https://doi.org/10.1371/journal.pone.0251784

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Abstract

We evaluated whether the water dispersibility of lactic acid bacteria (Enterococcus faecalis KH2) affects their efficacy. When cultured lactic acid bacteria are washed, heat-killed, and powdered, adhesion occurs between results in aggregation (non-treated lactic acid bacteria, n-LAB). However, dispersed lactic acid bacteria (d-LAB) with a lower number of aggregates can be prepared by treating them with a high-pressure homogenizer and adding an excipient during powdering. Mice were administered n-LAB or d-LAB Peyer's patches in the small intestine were observed. Following n-LAB administration, a high amount of aggregated bacteria drifting in the intestinal mucosa was observed; meanwhile, d-LAB reached the Peyer's patches and was absorbed into them. Evaluation in a mouse influenza virus infection model showed that d-LAB was more effective than n-LAB in the influenza yield of bronchoalveolar lavage fluids on day 3 post-infection and neutralizing antibody titers of sera and influenza virus-specific immunoglobulin A in the feces on day 14 post-infection. Therefore, the physical properties of lactic acid bacteria affect their efficacy; controlling their water dispersibility can improve their effectiveness.

Highlights

Lactic acid bacteria (LAB) play an important role in various fermentation processes
The particle sizes of approximately 55 and 0.7 μm were found to be more abundant for non-treated LAB” (n-LAB) and dispersed lactic acid bacteria (d-LAB), respectively size
The mean particle size of d-LAB was smaller than that of n-LAB [0.679 vs. 35.454 μm; the median was 0.633 μm for d-LAB compared with 40.761 μm for n-LAB (Table 1)]

Summary

Introduction

In the book “Essais Optimistes [1],” by the Russian microbiologist Metchnikov, he advocated the consumption of yogurt to increase life expectancy. This led to a flurry of research on the health benefits of LAB. The isolation and cultivation of LAB has rendered its consumption convenient. The active ingredients present in LAB, including lipoteichoic acid [10] and nucleic acid [11], are involved in modulating the immune response. LAB are used in food supplements, beverages, confectionery, cereals, and others.

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