Shaping the Future of Probiotics and Prebiotics.

Recent and ongoing developments in microbiome science are enabling new frontiers of research for probiotics and prebiotics. Novel types, mechanisms, and applications currently under study have the potential to change scientific understanding as well as nutritional and healthcare applications of these interventions. The expansion of related fields of microbiome-targeted interventions, and an evolving landscape for implementation across regulatory, policy, prescriber, and consumer spheres, portends an era of significant change. In this review we examine recent, emerging, and anticipated trends in probiotic and prebiotic science, and create a vision for broad areas of developing influence in the field.

Criteria to Qualify Microorganisms as "Probiotic" in Foods and Dietary Supplements.

Still relevant after 19 years, the FAO/WHO definition of probiotics can be translated into four simple and pragmatic criteria allowing one to conclude if specific strains of microorganisms qualify as a probiotic for use in foods and dietary supplements. Probiotic strains must be (i) sufficiently characterized; (ii) safe for the intended use; (iii) supported by at least one positive human clinical trial conducted according to generally accepted scientific standards or as per recommendations and provisions of local/national authorities when applicable; and (iv) alive in the product at an efficacious dose throughout shelf life. We provide clarity and detail how each of these four criteria can be assessed. The wide adoption of these criteria is necessary to ensure the proper use of the word probiotic in scientific publications, on product labels, and in communications with regulators and the general public.

Viral Infections, the Microbiome, and Probiotics.

Viral infections continue to cause considerable morbidity and mortality around the world. Recent rises in these infections are likely due to complex and multifactorial external drivers, including climate change, the increased mobility of people and goods and rapid demographic change to name but a few. In parallel with these external factors, we are gaining a better understanding of the internal factors associated with viral immunity. Increasingly the gastrointestinal (GI) microbiome has been shown to be a significant player in the host immune system, acting as a key regulator of immunity and host defense mechanisms. An increasing body of evidence indicates that disruption of the homeostasis between the GI microbiome and the host immune system can adversely impact viral immunity. This review aims to shed light on our understanding of how host-microbiota interactions shape the immune system, including early life factors, antibiotic exposure, immunosenescence, diet and inflammatory diseases. We also discuss the evidence base for how host commensal organisms and microbiome therapeutics can impact the prevention and/or treatment of viral infections, such as viral gastroenteritis, viral hepatitis, human immunodeficiency virus (HIV), human papilloma virus (HPV), viral upper respiratory tract infections (URTI), influenza and SARS CoV-2. The interplay between the gastrointestinal microbiome, invasive viruses and host physiology is complex and yet to be fully characterized, but increasingly the evidence shows that the microbiome can have an impact on viral disease outcomes. While the current evidence base is informative, further well designed human clinical trials will be needed to fully understand the array of immunological mechanisms underlying this intricate relationship.

Antimicrobial susceptibility testing of lactic acid bacteria and bifidobacteria by broth microdilution method and Etest.

We applied two methods of broth microdilution and Etest for measuring minimal inhibition concentration (MIC) of lactic acid bacteria and bifidobacteria for 15 antimicrobial agents to compare the feasibility, reproducibility, and equivalence of the two methods. Both methods were originally described by the European projects PROSAFE and ACE-ART. In 84% combinations of strains and antimicrobial agents MIC differences between the two methods were within one Log(2) dilution. In the case of rifampicin the difference between the two methods was more than ten-fold. We further determined MICs of 70 strains (14 strains of Lactobacillus delbrueckii ssp. bulgaricus, 16 strains of Lactococcus lactis, 30 strains of Streptococcus thermophilus, and 10 strains of Bifidobacterium longum) by the broth microdilution method. In most cases, MIC distributions were uni-modal and within 5 Log(2) dilutions except for the MIC distribution of L. lactis to the aminoglycoside group which was broader. These data are a good basis for improving knowledge of antimicrobial susceptibility of lactic acid bacteria and bifidobacteria, and can be used to revise tentative epidemiological cut-off values.

Osmoregulation in Lactococcus lactis: BusR, a transcriptional repressor of the glycine betaine uptake system BusA.

The busA (opuA) locus of Lactococcus lactis encodes a glycine betaine uptake system. Transcription of busA is osmotically inducible and its induction after an osmotic stress is reduced in the presence of glycine betaine. Using a genetic screen in CLG802, an Escherichia coli strain carrying a lacZ transcriptional fusion expressed under the control of the busA promoter, we isolated a genomic fragment from the L. lactis subsp. cremoris strain MG1363, which represses transcription from busAp. The cloned locus responsible for this repression was identified as a gene present upstream from the busA operon, encoding a putative DNA binding protein. This gene was named busR. Electrophoretic mobility shift and footprinting experiments showed that BusR is able to bind a site that overlaps the busA promoter. Overexpression of busR in L. lactis reduced expression of busA. Its disruption led to increased and essentially constitutive transcription of busA at low osmolarity. Therefore, BusR is a major actor of the osmotic regulation of busA in L. lactis.