Bile acids (BAs) play a crucial role in the human body’s defense against infections caused by bacteria, fungi, and viruses. BAs counteract infections not only through interactions with intestinal bacteria exhibiting bile salt hydrolase (BSH) activity but they also directly combat infections. Building upon our research group’s previous discoveries highlighting the role of BAs in combating infections, we have initiated an in-depth investigation into the interactions between BAs and intestinal microbiota. Leveraging the existing literature, we offer a comprehensive analysis of the relationships between BAs and 16 key microbiota. This investigation encompasses bacteria (e.g., Clostridioides difficile (C. difficile), Staphylococcus aureus (S. aureus), Escherichia coli, Enterococcus, Pseudomonas aeruginosa, Mycobacterium tuberculosis (M. tuberculosis), Bacteroides, Clostridium scindens (C. scindens), Streptococcus thermophilus, Clostridium butyricum (C. butyricum), and lactic acid bacteria), fungi (e.g., Candida albicans (C. albicans) and Saccharomyces boulardii), and viruses (e.g., coronavirus SARS-CoV-2, influenza virus, and norovirus). Our research found that Bacteroides, C. scindens, Streptococcus thermophilus, Saccharomyces boulardii, C. butyricum, and lactic acid bacteria can regulate the metabolism and function of BSHs and 7α-dehydroxylase. BSHs and 7α-dehydroxylase play crucial roles in the conversion of primary bile acid (PBA) to secondary bile acid (SBA). It is important to note that PBAs generally promote infections, while SBAs often exhibit distinct anti-infection roles. In the antimicrobial action of BAs, SBAs demonstrate antagonistic properties against a wide range of microbiota, with the exception of norovirus. Given the intricate interplay between BAs and intestinal microbiota, and their regulatory effects on infections, we assert that BAs hold significant potential as a novel approach for preventing and treating microbial infections.

Bile acids (BAs) play a crucial role in the human body's defense against infections caused by bacteria, fungi, and viruses. BAs counteract infections not only through interactions with intestinal bacteria exhibiting bile salt hydrolases (BSHs) activity but also directly combat infections. Building upon our research group's previous discoveries highlighting the role of BAs in combating infections, we have initiated an in-depth investigation into the interactions between BAs and microbiota. Leveraging existing literature, we offer a comprehensive analysis of the relationships between BAs and 16 key microbiota. This investigation encompasses bacteria (e.g., Clostridioides difficile, Staphylococcus aureus, Escherichia coli, Enterococcus, Pseudomonas aeruginosa, Mycobacterium tuberculosis, Bacteroides, Clostridium scindens, Streptococcus thermophilus, Saccharomyces boulardii, Clostridium butyricum, Lactic Acid Bacteria), fungi (e.g., Candida albicans), and viruses (e.g., Coronavirus SARS-CoV-2, influenza virus, norovirus). Our research underscores the critical role of the interplay between BAs and intestinal microbiota, including Bacteroides, Clostridium scindens, Streptococcus thermophilus, Saccharomyces boulardii, Clostridium butyricum, and Lactic Acid Bacteria, in maintaining intestinal homeostasis and combating infections. It is imperative to note that Primary bile acid (PBA) and Secondary bile acid (SBA) often exhibit distinct roles in the anti-infection process. In the antimicrobial action of BAs, SBA demonstrate antagonistic properties against a wide range of microbiota, with the exception of Norovirus. Given the intricate interplay between BAs and intestinal microbiota, and their regulatory effects on infections, we assert that BAs hold significant potential as a novel approach for preventing and treating intestinal microbial infections.

SUMMARY: The human gut microbiotas constitute a complex microecosystem essential for host homeostasis. Among its metabolites, short-chain fatty acids (SCFAs) act as key signaling molecules linking microbial activity to host immunity and barrier function. Based on existing literature, we conducted a comprehensive analysis of the interaction between SCFAs and 11 key gut pathogens. These pathogens include bacteria (i.e., Staphylococcus aureus , Clostridioides difficile, Salmonella spp. , Campylobacter jejuni, Klebsiella pneumoniae, Vibrio cholerae ), fungi (i.e., Candida albicans ), and viruses (i.e., SARS-CoV-2, influenza virus, respiratory syncytial virus, rotavirus). In terms of antibacterial effects, SCFAs exhibit antibacterial activity against most gut microorganisms, but they support the colonization of a few species (i.e., Campylobacter jejuni ). Given the complex interactions between SCFAs and the gut microbiota, as well as their regulatory roles in infection, further investigation of the microbiota-SCFA axis is essential for developing effective strategies to prevent and treat infectious diseases. This review systematically summarizes the mechanism and clinical evidence of SCFAs in microbial infections to provide novel ideas for infectious disease management.