Sodium butyrate inhibits Staphylococcus aureus internalization in bovine mammary epithelial cells and induces the expression of antimicrobial peptide genes

Antimicrobial peptide elicitors: New hope for the post-antibiotic era

Antimicrobial peptides or host defense peptides are fundamental components of human innate immunity. Recent and growing evidence suggests they have a role in a broad range of diseases, including cancer, allergies and susceptibility to infection, including HIV/AIDS. Antimicrobial peptide elicitors (APEs) are physical, biological or chemical agents that boost human antimicrobial peptide expression. The current knowledge of APEs and their potential use in the treatment of human infectious diseases are reviewed, and a classification system for APEs is proposed. The efficient use of APEs in clinical practice could mark the beginning of the urgently needed post-antibiotic era, but further trials assessing their efficacy and safety are required.

Cholecalciferol (vitamin D) differentially regulates antimicrobial peptide expression in bovine mammary epithelial cells: implications during Staphylococcus aureus internalization

Vitamin D has immunomodulatory functions regulating the expression of host defense genes. The aim of this study was to determine the effect of cholecalciferol (vitamin D3) on S. aureus internalization into bovine mammary epithelial cells (bMEC) and antimicrobial peptide (AP) mRNA expression. Cholecalciferol (1-200 nM) did not affect S. aureus growth and bMEC viability; but it reduced bacterial internalization into bMEC (15-74%). Also, bMEC showed a basal expression of all AP genes evaluated, which were induced by S. aureus. Cholecalciferol alone or together with bacteria diminished tracheal antimicrobial peptide (TAP) and bovine neutrophil β-defensin (BNBD) 5 mRNA expression; while alone induced the expression of lingual antimicrobial peptide (LAP), bovine β-defensin 1 (DEFB1) and bovine psoriasin (S100A7), which was inhibited in the presence of S. aureus. This compound (50 nM) increased BNBD10 mRNA expression coinciding with the greatest reduction in S. aureus internalization. Genes of vitamin D pathway (25-hydroxylase and 1 α-hydroxylase) show basal expression, which was induced by cholecalciferol or bacteria. S. aureus induced vitamin D receptor (VDR) mRNA expression, but not in the presence of cholecalciferol. In conclusion, cholecalciferol can reduce S. aureus internalization and differentially regulates AP expression in bMEC. Thus, vitamin D could be an effective innate immunity modulator in mammary gland, which leads to a better defense against bacterial infection.

Destructive effects of butyrate on the cell envelope of Helicobacter pylori

Helicobacter pylori can be found in the oral cavity and is mostly detected by the use of PCR techniques. Growth of H. pylori is influenced by various factors in the mouth, such as the oral microflora, saliva and other antimicrobial substances, all of which make colonization of the oral cavity by H. pylori difficult. In the present study, we analysed the effect of the cell supernatant of a representative periodontal bacterium Porphyromonas gingivalis on H. pylori and found that the cell supernatant destroyed the H. pylori cell envelope. As P. gingivalis produces butyric acid, we focused our research on the effects of butyrate and found that it significantly inhibited the growth of H. pylori. H. pylori cytoplasmic proteins and DNA were detected in the extracellular environment after treatment with butyrate, suggesting that the integrity of the cell envelope was compromised and indicating that butyrate has a bactericidal effect on H. pylori. In addition, levels of extracellular H. pylori DNA increased following treatment with the cell supernatant of butyric acid-producing bacteria, indicating that the cell supernatant also has a bactericidal effect and that this may be due to its butyric acid content. In conclusion, butyric acid-producing bacteria may play a role in affecting H. pylori colonization of the oral cavity.

The influence of Staphylococcus aureus on gut microbial ecology in an in vitro continuous culture human colonic model system

An anaerobic three-stage continuous culture model of the human colon (gut model), which represent different anatomical areas of the large intestine, was used to study the effect of S. aureus infection of the gut on the resident faecal microbiota. Studies on the development of the microbiota in the three vessels were performed and bacteria identified by culture independent fluorescence in situ hybridization (FISH). Furtheremore, short chain fatty acids (SCFA), as principal end products of gut bacterial metabolism, were measured along with a quantitative assessment of the predominant microbiota. During steady state conditions, numbers of S. aureus cells stabilised until they were washed out, but populations of indigenous bacteria were transiently altered; thus S. aureus was able to compromise colonisation resistance by the colonic microbiota. Furthermore, the concentration of butyric acid in the vessel representing the proximal colon was significantly decreased by infection. Thus infection by S. aureus appears to be able to alter the overall structure of the human colonic microbiota and the microbial metabolic profiles. This work provides an initial in vitro model to analyse interactions with pathogens.