The gastrointestinal tract is a complex ecosystem that associates a resident microbiota and cells of various phenotypes lining the epithelial wall expressing complex metabolic activities. The resident microbiota in the digestive tract is a heterogeneous microbial ecosystem containing up to 1×1014 colony-forming units (CFUs) of bacteria. The intestinal microbiota plays an important role in normal gut function and maintaining host health. The host is protected from attack by potentially harmful microbial microorganisms by the physical and chemical barriers created by the gastrointestinal epithelium. The cells lining the gastrointestinal epithelium and the resident microbiota are two partners that properly and/or synergistically function to promote an efficient host system of defence. The gastrointestinal cells that make up the epithelium, provide a physical barrier that protects the host against the unwanted intrusion of microorganisms into the gastrointestinal microbiota, and against the penetration of harmful microorganisms which usurp the cellular molecules and signalling pathways of the host to become pathogenic. One of the basic physiological functions of the resident microbiota is that it functions as a microbial barrier against microbial pathogens. The mechanisms by which the species of the microbiota exert this barrier effect remain largely to be determined. There is increasing evidence that lactobacilli and bifidobacteria, which inhabit the gastrointestinal microbiota, develop antimicrobial activities that participate in the host's gastrointestinal system of defence. The objective of this review is to analyze the in vitro and in vivo experimental and clinical studies in which the antimicrobial activities of selected lactobacilli and bifidobacteria strains have been documented.

Antagonistic activities of lactobacilli and bifidobacteria against microbial pathogens

Kwashiorkor, an enigmatic form of severe acute malnutrition, is the consequence of inadequate nutrient intake plus additional environmental insults. To investigate the role of the gut microbiome, we studied 317 Malawian twin pairs during the first 3 years of life. During this time, half of the twin pairs remained well nourished, whereas 43% became discordant, and 7% manifested concordance for acute malnutrition. Both children in twin pairs discordant for kwashiorkor were treated with a peanut-based, ready-to-use therapeutic food (RUTF). Time-series metagenomic studies revealed that RUTF produced a transient maturation of metabolic functions in kwashiorkor gut microbiomes that regressed when administration of RUTF was stopped. Previously frozen fecal communities from several discordant pairs were each transplanted into gnotobiotic mice. The combination of Malawian diet and kwashiorkor microbiome produced marked weight loss in recipient mice, accompanied by perturbations in amino acid, carbohydrate, and intermediary metabolism that were only transiently ameliorated with RUTF. These findings implicate the gut microbiome as a causal factor in kwashiorkor.

http://www.humeco.m.u-tokyo.ac.jp/individuals/umezaki/PDF_files/Meeting/Malawi_Gutmicrobiome_Kwashiorkor_Science2013.pdf

Gut microbiomes of Malawian twin pairs discordant for kwashiorkor

Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host There is now mounting evidence that selected probiotic strains can provide health benefits to their human hosts Numerous clinical trials show that certain strains can improve the outcome of intestinal infections by reducing the duration of diarrhea Further investigations have shown benefits in reducing the recurrence of urogenital infections in women, while promising studies in cancer and allergies require research into the mechanisms of activity for particular strains and better-designed trials At present, only a small percentage of physicians either know of probiotics or understand their potential applicability to patient care Thus, probiotics are not yet part of the clinical arsenal for prevention and treatment of disease or maintenance of health The establishment of accepted standards and guidelines, proposed by the Food and Agriculture Organization of the United Nations and the World Health Organization, represents a key step in ensuring that reliable products with suitable, informative health claims become available Based upon the evidence to date, future advances with single- and multiple-strain therapies are on the horizon for the management of a number of debilitating and even fatal conditions

/pdf/potential-uses-of-probiotics-in-clinical-practice-1id3pis1h4.pdf

Potential Uses of Probiotics in Clinical Practice

B. K OS, J. SUSKOVIC ´ ,S. V U K O V I C´ ,M. SIMPRAGA, J. F RECE A ND S. M ATOSIC ´ . 2003. Aims: To investigate aggregation and adhesiveness of Lactobacillus acidophilus M92 to porcine ileal epithelial cells in vitro, and the influence of cell surface proteins on autoaggregation and adhesiveness of this strain. Methods and Results: Lactobacillus acidophilus M92 exhibits a strong autoaggregating phenotype and manifests a high degree of hydrophobicity determined by microbial adhesion to xylene. Aggregation and hydrophobicity were abolished upon exposure of the cells to pronase and pepsin. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of cell surface proteins revealed the presence of potential surface layer (S-layer) proteins, approximated at 45 kDa, in L. acidophilus M92. The relationship between autoaggregation and adhesiveness to intestinal tissue was investigated by observing the adhesiveness of L. acidophilus M92 to porcine ileal epithelial cells. Removal of the S-layer proteins by extraction with 5 mol l )1 LiCl reduced autoaggregation and in vitro adhesion of this strain. Conclusions: These results demonstrate that there is relationship between autoaggregation and adhesiveness ability of L. acidophilus M92, mediated by proteinaceous components on the cell surface. Significance and Impact of the Study: This investigation has shown that L. acidophilus M92 has the ability to establish in the human gastrointestinal tract, which is an important determinant in the choice of probiotic strains.

/pdf/adhesion-and-aggregation-ability-of-probiotic-strain-4ddzyk5p5a.pdf

Adhesion and aggregation ability of probiotic strain Lactobacillus acidophilus M92

The ability of probiotic bacteria to adhere to the intestinal epithelium play an important role in colonization of the gastrointestinal tract, preventing their elimination by peristalsis and providing a competitive advantage in this ecosystem. To identify bacterial traits related to adhesion the probiotic strain L. acidophilus M92 was examined for autoaggregation ability and cell surface hydrophobicity L. acidophilus M92 exhibits a strong autoaggregation phenotype and also coaggregation with some pathogen microorganisms that may form a barrier that prevents their colonization. The examined probiotic strain manifests a good degree of hydrophobicity determined by microbial adhesion to hydrocarbons. Aggregation and hydrophobicity were abolished upon exposure of the cells to pronase, which suggests the possible role of cell surface layer (S-layer) proteins, approximated at 45 kDa, in a L. acidophilus M92. The relationship between autoaggregation and adhesion ability to intestinal tissue was investigated by observing the adhesivity of L. acidophilus M92 to porcine ileal epithelial cells. Removal of the S-layer proteins by extraction with 5 M LiCl reduced autaggregation and in vitro adhesion of this strain.

Aims: The study of two human strains of Lactobacillus to be used as probiotics in the gastrointestinal tract.



Methods and Results: The Lactobacillus acidophilus UO 001 and Lact. gasseri UO 002, were resistant to the gastrointestinal conditions (pH 2 and 3, presence of pepsin, pancreatin or bile salts), the resistance was enhanced in the presence of skimmed milk. Additionally, adhered to Caco-2 cells through glycoproteins in Lact. gasseri and carbohydrates in the case of Lact. acidophilus. These strains are able to inhibit the growth of certain enteropathogens: Salmonella, Listeria and Campylobacter without interfering with the normal microbiota of the gastrointestinal tract, as stated by using the mixed culture and the spot agar test. Finally, strongly adherent Lact. gasseri were found to inhibit the attachment of Escherichia coli O111 to intestinal Caco-2 cells under the condition of exclusion.



Conclusions: These results indicate that the two strains of Lactobacillus from human origin present important properties for survival in, and colonization of, the gastrointestinal tract, that give them potential probiotic.



Significance and Impact of the Study: Two strains of Lactobacillus isolated from human vagina of healthy premenopausal women could be promising candidates to be used in the preparation of probiotic products and for their use as health-promoting bacteria.

Probiotic properties of human lactobacilli strains to be used in the gastrointestinal tract.

Three strains of Lactobacillus, identified as Lactobacillus acidophilus, Lactobacillus gasseri, and Lactobacillus jensenii, were selected from among 70 isolates from the vaginas of healthy premenopausal women for properties relevant to mucosal colonization or antagonism. All three self-aggregated and adhered to epithelial vaginal cells, displacing well-known vaginal pathogens, such as G. vaginalis, and inhibiting the growth in vitro of Escherichia coli and Streptococcus agalactiae. The surface components involved in self-aggregation appeared to be proteins for L. gasseri and lipoproteins for L. acidophilus and L. jensenii, as judged by susceptibility to treatment with appropriate degrading enzymes. The factors responsible for adherence to epithelial vaginal cells seemed to be glycoproteins (L. acidophilus and L. gasseri) and carbohydrate (L. jensenii). The receptors of the vaginal cells were glycolipids, which presumably were the targets of the competition observed between the lactobacilli and the pathogenic microbes.

Adherence of Human Vaginal Lactobacilli to Vaginal Epithelial Cells and Interaction with Uropathogens

Lactobacillus gasseri 2459, isolated from the human vagina, exhibits a strong autoaggregating phenotype. Filter-sterilized spent supernatants of this strain promote aggregation of Lact. plantarum LL441 and Enterococcus faecalis EF. Aggregation was abolished upon exposure of the cells to proteases and, in the case of Ent. faecalis, to metaperiodate, which suggests the involvement of cell-surface proteins and glycoproteins, respectively, in the aggregation phenotype. In accordance with this, a 75 kDa surface protein, and possibly another of approximately 94 kDa, appears in Lact. plantarum LL441 cultures incubated with Lact. gasseri culture supernatants. The diffusible aggregation promoting factor was purified from stationary phase culture supernatants and determined to be a 2 kDa hydrophilic peptide active at pH 3-4 and stable at neutral and acid pH. The activity was resistant to heat, chymotrypsin, chelating agents, triton X-100 and reducing agents, but sensitive to other proteases and SDS.

Characterization of the aggregation promoting factor from Lactobacillus gasseri, a vaginal isolate

The characteristics required of lactobacilli as probiotics are the following: beneficial function, easy cultivation, nonpathogenicity, adhesion, and population stability. Several studies have assessed the potential of lactobacilli in the prevention or treatment of certain genitourinary tract infections such as bacterial vaginosis, vaginitis, or urinary tract infections. The main goal of therapy with biotherapeutic agents should be to prevent overgrowth of a pathogen until such a time that the normal microbiota can be reestablished. The possibility of using lactobacilli is promising, especially in pregnant women and in the case of patients with recurrent genitourinary tract infections produced by strains with resistance to several antibiotics. In addition, probiotic therapy is considered as "natural" and without side effects in contrast with conventional pharmaceutical treatments, but there is a limited array of tested biotherapeutic agents and a lack of pharmacokinetic data.

Potential Role of Lactobacilli as Prophylactic Agents Against Genital Pathogens

Aims: The partial characterization of a bacteriocin produced by a human Lactobacillus delbrueckii isolate with probiotic potential.



Methods and Results: A bacterocin, UO004, was partially purified by cation exchange followed by a hydrophobic interaction column, biochemically characterized and the N-terminal region sequenced. Bacteriocin UO004 was found to be a hydrophobic, heat-stable polypeptide with an apparent molecular mass of 6 kDa. It was also stable and active over a wide pH range.



Conclusions: The active compound was proteinaceous, heat-stable, and had a bactericidal (and bacteriolytic) mode of action on a limited number of micro-organisms. Such a narrow spectrum of activity is typical for bacteriocins produced by intestinal Lactobacillus.



Significance and Impact of the Study: Bacteriocin UO004 from a probiotic strain is a new compound that does not share any homology with any other known lactic acid bacteria bacteriocin. Furthermore, Lact. delbrueckii is regarded as a suitable starter for the production of fermented milks.

https://sfamjournals.onlinelibrary.wiley.com/doi/epdf/10.1046/j.1365-2672.2001.01403.x

Soledad Boris

Papers

Probiotic properties of human lactobacilli strains to be used in the gastrointestinal tract.

Adherence of Human Vaginal Lactobacilli to Vaginal Epithelial Cells and Interaction with Uropathogens

Characterization of the aggregation promoting factor from Lactobacillus gasseri, a vaginal isolate

Potential Role of Lactobacilli as Prophylactic Agents Against Genital Pathogens

Partial characterization of a bacteriocin produced by Lactobacillus delbrueckii subsp. lactis UO004, an intestinal isolate with probiotic potential