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MVST 1B (Subject) / BOD - Microbiology (Lesson)
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- Bacterial immune evasion Hostile environment lack of iron → siderophores stomach acid → urease reaction, e.g. shigella, H. pylori Macrophages prevent uptake: a) paralyse; b) inhibit chemotaxis (C5a peptidase); c) antiphagocytic capsule; d) kill survive inside Complement: LPS-O antigen Antibody Evade recognition: a) host mimickry; b) phase variation; c) antigenic variation inactivate: a) cleave IgA; b) bind Fc component Examples !?
- Bacterial virulence factors General specialised, regulated extrachromosomal plasmids / bacteriophages; PathoGenicity Island's exported, secreted, or delivered Colonalisation adhesins, e.g. pili pedestals biofilms Invasion Zipper - RME; invasins, e.g. fibronectin Trigger - needles After invasion Spread through cells, e.g. Shigella, Listeria) Shigella stays in vacuole? extracellular, e.g. pyogeniic cooci: enzymes (collagenase, hyaluronidase, staphylokinase, coagulase, DNAse) Evasion of host defence Exotoxins
- Mutations in cancer proliferation death signalling x4 movement adhesion repair Oncogenes vs TSG's, examples?
- Oncogene activation retrovirus - carrying vs promoter/enhancer insertion point mutation - K-Ras, Gly → Val amplification -- EGFR truncation - (APC), EGFR inapropriate regulation of expression - myc transposition - bcr/abl 9-22 Ph+ CML
- DNA repair Mismatch repair: MLH1/MSH2 → HNPPC Nucleotide excision repair → xeroderma pigmentosum Strand break repair: brca-1/2 → breast/ovarian cancer Fanconi anaemia DNA repair → Fanconi anaemia
- Viruses as causes of cancer How to implicate Epidemiology: case-control, prospective Prophylactic vaccination? viral genes in tumour cells? Mechanisms Chronic damage and repair Oncogene activation TSG inactivation Example: Cervical cancer & HPV 16 & 18
- Systemic pathogenic fungi Histoplasma: dimorphic
- Systemic opportunistic fungi --
- Superficial viral infections Common cold influenza gastroenteritis (rota virus)
- Systemic viral infections smallpox measles chickenpox foot and mouth disease varicella zoster
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- Acute viral infections Variola Rotavirus Picornaviruses Influenza measles rubella
- Thrombosis Structure: lines of Zahn; arterial vs venous Virchow's triad: changes in blood flow / constituents / vessel wall fate embolus: routes of spread
- Food-borne diseases E.coli 0157 Staph aureus Salmonella spp
- Autoimmune diseases Mechanisms Direct antibody-mediated ~ HS type II myasthenia gravis rheumatic fever Immune complex mediated ~ HS type II; SLE T cell mediated ~ HS type IV Type I diabetes rheumatoid arthritis multiple sclerosis Animal models Genetic (MHC, sex) vs environmental factors Initiation and perpetuation
- Hyperplasia Nuclear pleiomorphism increased nucleus:cytopalsm ratio hyperchromatic nuclei extension of proliferating compartment anaplasia?
- HPV16 Causes cervical cancer E6 → degrades p53 E7 → sequesters Rb
- Tumour suppressor genes Rb p53 Bcl-2 DNA repair: MLH-1/MSH-2, XP, AT, FA Gene product, function, how deactivated
- Vaccination (bacteria) Live (attenuated) Killed (inactivated) Toxoid DPT = toxoid / dead / toxoid BCG = live typhoid, cholera = killed pneumonia, meningits = subunits
- Macrophages Kuppfer cells microglia epithelioid cell osteoclasts