Oversight pathogens

Question 1

Stages of infection

Accepted Answer

Encounter --> Colonisation/attachment --> Penetration --> Spread --> Damage --> Resolution

Question 2

Causes of disease in infection (3)

Accepted Answer

1. Damage caused directly by the virus (cytolytic viruses), bacteria (toxins) or parasite 2. Damage mediated via overreactive innate immune response 3. Damage mediated via overreactive acquired immune mechanisms ("hypersensitivity")

Question 3

Gell and Coomber Hypersensitivity

Accepted Answer

1. Type I (Allergy) - anaphylatctic/immediate type - atrophy, asthma, anaphylaxis - mediated by IgE 2. Type II (Antibody-mediated cytotoxicity) - Blood transfusions: host antibodies react with foreign antigens on the incompatible transfused blood cells and mediate destruction of these cells by activating the complement system to create pores in the membrane of the foreign cell or by mediating cell destruction by antibody-dependent cell-mediated cytotoxicity (ADCC). In this process, cytotoxic cells with Fc-receptors bind to the Fc-region of antibodies on target cells and promote killing of the cells. 3. Type III (Immune complexes induced inflammation) - antigen-antibody complexes (immune complexes) are deposit into tissues and organs where they cause inflammations (activation complement system, mast cells,...) --> tissue damage --> e.g. rheumatoid arthritis 3. Type IV (Delayed type of hypersensitivity) - Helper T cells are activated by an APC. When the antigen is presented again in the future, the memory T cells will activate macrophages --> chronic inflammatory response - e.g. Tuberculosis

Question 4

Routes of transmission and reservoirs

Accepted Answer

1. Direct - person to person 2. Vector-vertebrate (e.g. yellow fever, plague) 3. Vector: biting arthropod (e.g. malaria)

Question 5

Mechanisms enabling bacteria to colonise the host

Accepted Answer

1. Pili 2. Adhesin proteins (virulence factors) 3. Biofilms - Aggregate of microorganisms in which cells that are frequently embedded within a self-produced matrix of extracellular polymeric substances (EPSs) adhere to each other and/or to a surface

Question 6

How do bacteria evade the host immune response?

Accepted Answer

1. Secreted factors that enable free movement in the host: Hyaluronidase - destroys CT, Coagulase - conversion of fibrinogen into fibrin leading to protection from phagocytosis, Streptokinase - liquifies pus and aids spread,... 2. Evasion of the immune system: resist lysis of antibody and complement by the anti-opsonising protein (e.g. Protein A - antobody bound to bacteria by Fc instead antigen-binding site which prevents phagocytosis), Catalase (enzyme whic breaks down H2O2), Leukocidin (pore-forming toxin which kill leucocytes)

Question 7

Common bacterial pathogens and causes diseases

Accepted Answer

1. Staphylococci a) S. aureus - causes abscesses/pus and erodes overlying skin (Folliculitis). Can also invade deeper tissues (Cabuncle) and cause the skalded skin syndrome (epidermolytic toxin destroys cellular connections in epidermis) 2. Streptococci a) alpha-haemolytic - (Pneumococci) b) beta-haemolytic (S. pyogenes, S. agalactiae) --> can cause streptococcal pharyngitis and impetigo (non-evasive), but can also be more invasive 3. Clostridia - C. botulinum, C. tetani, C.perfringens (all anaerobes, create spores, found in soil and animal faeces, killed by O2) --> can cause Tetanus, gas gangrene

MCB (Fach) / Oversight pathogens (Lektion)