A new study from the Quadram Institute and Jiangnan University has highlighted how different strains of probiotic bacteria differed in their ability to restore the microbiota of mice that had received antibiotics.
Antibiotics are administered to combat disease-causing bacteria, but their effects are indiscriminate and they can damage the populations of microbes that make up a healthy microbiome. This can drastically change the balance of microbes in the microbiome, putting it into a state known as dysbiosis. Dysbiosis has been linked to a number of conditions in both mice-models of disease and humans. Dysbiosis can also be characterised by inflammation and damage to the gut lining. It changes the profile of metabolites released by the bacteria, limiting the benefits of compounds such as short chain fatty acids (SCFAs), that are believed to play a role in maintain the gut lining.
In this new study, published in the Journal of Functional Foods, the researchers induced dysbiosis in the gut microbiome of mice using a therapeutic dose of the antibiotic ampicillin. Having confirmed the dysbiosis, they then treated mice with three different strains of Lactobacillus bacteria. There are over 150 different species of Lactobacillus bacteria, and they make up an important component of a healthy microbiome. They also occur in fermented foods, such as yogurt, and there has been a lot of interest in using them as probiotics to boost health.
The study compared three Lactobacillus strains (L. plantarum L. casei and L. rhamnosus) derived from fermented foods. These have been previously studied and characterised for their potential use as probiotics. The researchers measured how effective they were at restoring a diverse, healthy microbiome. They also analysed the metabolite profile, and combining this with the microbial composition data allowed a functional analysis of the restored microbiome. They also assessed measures of inflammation and permeability of the gut lining.
As expected from previous studies, the antibiotic treatment reduced the microbial diversity in the mice. The disturbed microbiomes had enhanced levels of bacteria that are also enhanced in humans suffering from gastroenteritis, irritable bowel syndrome and inflammation.
The findings of the study showed that although all three Lactobacillus strains restored the microbiome more quickly than without any probiotics, Lactobacillus casei was particularly effective. Combining the evidence from analysing the microbes and their metabolites, it could be seen that this strain was restoring microbial families that produce SCFAs, especially acetate and butyrate. There was also a reduction in inflammation-promoting compounds, either because of the SCFAs or through the restored microbiome.
Clinical trials in people will be needed before the results of this study can be extrapolated to humans, but it does highlight the importance of understanding the contributions of individual strains of bacteria and microbes to any health effects associated with the microbiome. Fermented foods usually have a mixture of different bacteria, so in assessing their effects we must be sure to know which specific strains are present. And as this study highlights, we need to combine knowledge of not just the species, but also how they function to fully appreciate how they may benefit our health.
The Quadram Institute is strategically supported by the Biotechnology and Biological Sciences Research Council (BBSRC). This study was supported by the National Natural Science Foundation, the National Natural Science Foundation of China Key Program, National First-Class Discipline Program of Food Science and Technology, BBSRC Newton Fund Joint Centre Award, the National Natural Science Foundation of China, National Natural Science Foundation of Jiangsu Province, National Natural Science Foundation of China and Collaborative innovation center of food safety and quality control in Jiangsu Province.
Reference: The divergent restoration effects of Lactobacillus strains in antibiotic-induced dysbiosis, Ying Shi Lee Kellingray, Gwenaelle Le Gall, Jianxin Zhao, Hao Zhang, Arjan Narbad, Qixiao Zhai, Wei Chen Journal of Functional Foods 51 (142-152) doi: 10.1016/j.jff.2018.10.011