17
Medical Microbiology (Subject) / Bacterial Pathogenesis (Lesson)
Advertisement
- Body defense 1.skin and mucosa (sebum, low pH, lysozme) 2.innate immunity (phagocytosis by neutrophiles and macrophages) 3.adaptive immunity (T-cells, B-cells, antibodies)
- Transmission 1.Contact: direct, indirect and droplet 2.vehicles: non animals waterborne,foodborne and airborne 3.vectors: animals, Arthropods, Mosquitos
- Portal of entry: Skin(Epidermis) defense 1.constant shedding of cells 2.antimicrobial chemicals 3.dendritic langerhans cells
- Portal of entry: Skin(Mucosa) defense 1.cell shedding 2.dendritic cells 3.secretion of mucus (trapping, transport, IgA)
- Parenteral Route lesion of skin allows entry
- Adhesion Adhesins bind to receptor proteins
- Adhesion: direct evidence 1.tissue tropism 2.limited host range 3.genetic specificity
- Adhesion: indirect evidence 1.Bacteria bind isolated receptor or receptor analogues 2.isolated adhesins bind to eukaryotic cells 3.Adhesion inhibited
- Adhesion inhibitors 1.isolated adhesin or receptor molecules 2.enzymes that destroy adhesin or receptor 3.antibodies specific to surface components
- Types of adhesins 1. polysacharides (capsule, biofilm) 2. fimbrae 3. non fimbral proteins
- Advertisement
- Capsule polysaccharide meshwork attached to cell wall may contain sialic acid or hyaluronic acid
- Biofilm: What is it? production of extracellular polysacharides polysacharides species specific: Dextran(poly alpha 1-6 glucose), Alginate (heteropolymer)
- Biofilm forming 1.induces attachement 2.colony sensing 3.release of microcolonies
- Biofilm advantages 1. Defense (physical stress, antibiotic sensitivity reduced, phagocytosis) 2. favourable environment 3. community (share extracellular enzymes, horizontal gene transfer)
- Biofilm: Diseases Urinary catheter infection by E.coli infection of artificial heart valves by S.epidermidis chronic lung infection in cystic fibrosis by P.aeruginosa chronic bladder infection by P.aeruginosa
- Fimbrial adhesins 2µm long 2-8nm thick one prot or major prot+tip
- Fimbrial adhesins special case EPEC Injects receptor(Tir) into cell, forms pedastal, attaches there