Bile salt biotransformations by human intestinal bacteria.

Polyphasic taxonomy, a consensus approach to bacterial systematics.

Summary: Bacteroides species are significant clinical pathogens and are found in most anaerobic infections, with an associated mortality of more than 19%. The bacteria maintain a complex and generally beneficial relationship with the host when retained in the gut, but when they escape this environment they can cause significant pathology, including bacteremia and abscess formation in multiple body sites. Genomic and proteomic analyses have vastly added to our understanding of the manner in which Bacteroides species adapt to, and thrive in, the human gut. A few examples are (i) complex systems to sense and adapt to nutrient availability, (ii) multiple pump systems to expel toxic substances, and (iii) the ability to influence the host immune system so that it controls other (competing) pathogens. B. fragilis, which accounts for only 0.5% of the human colonic flora, is the most commonly isolated anaerobic pathogen due, in part, to its potent virulence factors. Species of the genus Bacteroides have the most antibiotic resistance mechanisms and the highest resistance rates of all anaerobic pathogens. Clinically, Bacteroides species have exhibited increasing resistance to many antibiotics, including cefoxitin, clindamycin, metronidazole, carbapenems, and fluoroquinolones (e.g., gatifloxacin, levofloxacin, and moxifloxacin).

Bacteroides: the Good, the Bad, and the Nitty-Gritty

Commensal and pathogenic microorganisms must resist the deleterious actions of bile in order to survive in the human gastrointestinal tract. Herein we review the current knowledge on the mechanisms by which Gram-positive and Gram-negative bacteria contend with bile stress. We describe the antimicrobial actions of bile, assess the variations in bile tolerance between bacterial genera and examine the interplay between bile stress and other stresses. The molecular mechanisms underlying bile tolerance are investigated and the relationship between bile and virulence is examined. Finally, the potential benefits of bile research are briefly discussed.

The interaction between bacteria and bile

Probiotics are usually defined as microbial food supplements with beneficial effects on the consumers. Most probiotics fall into the group of organisms' known as lactic acid-producing bacteria and are normally consumed in the form of yogurt, fermented milks or other fermented foods. Some of the beneficial effect of lactic acid bacteria consumption include: (i) improving intestinal tract health; (ii) enhancing the immune system, synthesizing and enhancing the bioavailability of nutrients; (iii) reducing symptoms of lactose intolerance, decreasing the prevalence of allergy in susceptible individuals; and (iv) reducing risk of certain cancers. The mechanisms by which probiotics exert their effects are largely unknown, but may involve modifying gut pH, antagonizing pathogens through production of antimicrobial compounds, competing for pathogen binding and receptor sites as well as for available nutrients and growth factors, stimulating immunomodulatory cells, and producing lactase. Selection criteria, efficacy, food and supplement sources and safety issues around probiotics are reviewed. Recent scientific investigation has supported the important role of probiotics as a part of a healthy diet for human as well as for animals and may be an avenue to provide a safe, cost effective, and 'natural' approach that adds a barrier against microbial infection. This paper presents a review of probiotics in health maintenance and disease prevention.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2672.2006.02963.x

Probiotics and their fermented food products are beneficial for health.

There are several potential health or nutritional benefits possible from some species of lactic acid bacteria. Among these are: improved nutritional value of food, control of intestinal infections, improved digestion of lactose, control of some types of cancer, and control of serum cholesterol levels. Some potential benefits may result from growth and action of the bacteria during the manufacture of cultured foods. Some may result from growth and action of certain species of the lactic acid bacteria in the intestinal tract following ingestion of foods containing them. In selecting a culture to produce a specific benefit it is necessary to consider not only the wide variation among species of the lactic acid bacteria but also that among strains within a given species. With the possible exception of improving lactose utilization by persons who are lactose maldigestors, no specific health or nutritional claims can yet be made for the lactic acid bacteria.

Health and nutritional benefits from lactic acid bacteria

Importance of Bile Tolerance of Lactobacillus acidophilus Used as a Dietary Adjunct

Factors to consider when selecting a culture of Lactobacillus acidophilus as a dietary adjunct to produce a hypocholesterolemic effect in humans.

Objective: Two controlled clinical studies were performed to examine effects of consumption of one daily serving of fermented milk (FM) (yogurt) on serum lipids.Methods: In the first study, subjects were randomly allocated to FM containing Lactobacillus acidophilus L1 of human origin or to FM containing L. acidophilus ATCC 43211 of swine origin. In this single-blind study, subjects consumed one 200 ml serving of FM daily for 3 weeks. The second study was a double-blind, placebo-controlled, cross-over study. Subjects completed a 4-week first treatment, had a 2-week washout, and completed a second 4-week treatment. In the second study subjects consumed FM containing L. acidophilus L1 or placebo FM over 4 weeks.Results: In the first study, FM containing L. acidophilus L1 was accompanied by a 2.4% (p<0.05) reduction of serum cholesterol concentration. In the second study, strain L1 reduced serum cholesterol concentration by 3.2% (p<0.05) in the first treatment period. In the second treatment period there were...

Effect of fermented milk (yogurt) containing Lactobacillus acidophilus L1 on serum cholesterol in hypercholesterolemic humans.

Direct-fed microbials (DFM) have been shown to increase daily gain and feed efficiency in feed- lot cattle, enhance milk production in dairy cows, and improve health and performance of young calves. How- ever, their effects on performance have been mixed, and the mode of action remains unclear. Bacteria used as DFM have been defined as single or mixed cultures of live organisms, which, when fed to animals, beneficially affect the host. The original concept of feeding DFM to man and livestock was based primarily on the potential for beneficial intestinal effects, including the establish- ment of a desirable gut microflora and/or prevention of the establishment of pathogenic organisms. More re- cently, however, there has been some indication that certain bacterial DFM might have beneficial effects in the rumen, such as decreasing the potential for ruminal acidosis. In several experiments, supplementing feedlot cattle with lactate-utilizing and/or lactate-producing bacteria has been shown to improve feed efficiency and daily gain (approximately 2.5%), with little change in DMI. In addition, increased milk yield (0.75 to 2.0 kg/

Stanley E. Gilliland

Papers

Health and nutritional benefits from lactic acid bacteria

Importance of Bile Tolerance of Lactobacillus acidophilus Used as a Dietary Adjunct

Factors to consider when selecting a culture of Lactobacillus acidophilus as a dietary adjunct to produce a hypocholesterolemic effect in humans.

Effect of fermented milk (yogurt) containing Lactobacillus acidophilus L1 on serum cholesterol in hypercholesterolemic humans.

Bacterial direct-fed microbials in ruminant diets: Performance response and mode of action