title: Evaluation of capsular and acapsular strains of S. aureus in an experimental brain abscess model.
abstract: Brain abscesses are mainly caused by either direct or indirect inoculation of gram positive bacteria including Stapylococcus aureus (S. aureus) or Streptococcus species into the central nervous system. In the present study, we aimed to compare potential changes in brain abscess pathogenesis induced by two different strains of S. aureus, namely the laboratory strain RN6390 and the clinical isolate Reynolds. Although the Reynolds strain was expected to be more resistant to eradication by the host, due to the existence of a polysaccharide capsule, and subsequently to be more virulent, instead we found parenchymal damage and mortality rates to be more prominent following RN6390 infection. In contrast, the Reynolds strain proliferated faster and induced early expression of the chemokine CXCL2, matrix metalloproteinase-9 (MMP-9), and complement 3a and C5. Furthermore, there were early and more abundant infiltration of PMNs, T cells and erythrocyte extravasation in brain abscesses induced by the Reynolds strain. However, several immune parameters were not different between the two strains during the later stages of the disease. These results suggest that capsular S. aureus can modulate innate immunity and complement system activation differently than the acapsular strain RN6390, and the early changes induced by Reynolds strain may have an important impact on survival.
authors.affiliation: Department of Neurology, Holtom-Garrett Program in Neuroimmunology, University of Michigan Medical School, Ann Arbor, MI 48109, United States. nilufer@med.umich.ed
authors.forename: Nilufer
authors.initials: N
authors.lastname: Esen
authors.forename: Gail
authors.initials: G
authors.lastname: Wagoner
authors.forename: Napoleon
authors.initials: N
authors.lastname: Philips
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000276:immunology*; D015153:Blotting, Western; D001922:Brain Abscess / Q000276:immunology* / Q000382:microbiology*; D054426:Chemokine CXCL2 / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D020780:Matrix Metalloproteinase 9 / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D020556:Neutrophil Infiltration / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013203:Staphylococcal Infections / Q000276:immunology* / Q000382:microbiology*; D013211:Staphylococcus aureus
chemical_list: D054426:Chemokine CXCL2; D020780:Matrix Metalloproteinase 9