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MLT-Pathogenicity
Mircrobiology
| Question | Answer |
|---|---|
| What is pathogens? | A microbe whose relationship with its host is parasitic and results in infection and disease. |
| What is pathogenicity? | The potential of an organism to cause infection or disease. |
| What is virulent factor? | Any characteristic or structure of the microbe that facilitates to establish itself in the host, and cause damage. |
| Example of True pathogens? | Influenza virus, Poliovirus, Neisseria gonorrhoeae, Rabies, Malarial parasite |
| Example of opportunistic pathogens? | Candidas albica, E.coli, Staphylococcus aureus, Pseudomonas |
| The infectious doesage of a pathogen? | Coxiella burnetii (Q fever) - 1 cell Mycobacterium tuberculosis (TB) - 10 cells Neisseria gonorrhoeae (Gonorrhoea) - 1,000 cells Salmonella typhi (Typhoid) - 10,000 cells Vibrio cholera (Cholera) - 1,000,000,000 cells |
| Anti-2nd line defence(1)? | -Killing Phagocyte -Produce leukocidins, causes the lysosomes of pahagocytes to lyse -self-destruction of WBC -Staphylococci and Streptococci |
| Anti-2nd line defence(2)? | -Inhibition of chemotaxis -Produce chemicals that can interfere the movement of phagocytes towards the bacteria -Staphylococci and Clostridia |
| Anti-2nd line defence(3)? | -Escape from phagocytes -Possess a capsule which favours the organisms to slip away from the phagocytosis, eg. Streptococcus pneumoniae -Some produce Coagulase, the clot act as the shield for the microbes from phagocytosis, eg. Staphylococcus aureus |
| Anti-2nd line defence(4)? | -Resistance to digestion in phagocyte -by producing antioxidants, catalase in Staphylococci -have waxy cell wall which is resistant to enzyme digestion, e.g. Mycobacteria |
| Anti-2nd line defence(5)? | -Inhibition of complement -deposit sialic acid residues on their surfaces which prevents opsonization by complement components and impedes recognition by phagocytes |
| Anti-3rd line defence(1)? | -Inactivation of Antibody -Streptococcus pneumoniae -> IgA protease -> cleaves the Fc portion from IgA, no phagocytosis Staphylococcus aureus -> Fc portion receptor (Protein A) -> bind the antibody “upside down” -> no opsonization and phagocytosis |
| Anti-3rd line defence(2)? | -Hiding -Malaria parasite in red cells, which cannot present the foreign antigen to T cells -where areas no Ab, like Salmonella in the bile duct, rabies the salivary gland |
| Anti-3rd line defence(3)? | -Modifying the surface antigen -Antigenic drift -Antigenic shift -eg.Influenza |
| Anti-3rd line defence(4)? | -Immunosuppession -Human Immunodeficiency Virus (HIV) target CD4+ T lymphocytes (T helper cells), causing lysis -no B cells and cytotoxic T cell activation. |
| How does pathogens causing diseases? | 1.Direct damage: -secrete extracellular enzyme -produce exotoxins, endotoxins 2.Indirect damage -induce excessive or inappropriate host respond |
| How do the extracellular enzymes work? | 1.To dissolve the host’s defence barriers and promote the spread of microbes to deeper tissues. eg: Mucinase, Keratinase 2.To protect the microbes from immune response. eg. Coagulase |
| How does Mucinase work? | Digests the protective coating on mucous membrane in the gut -> Dysentery |
| How does Keratinase work? | Digests the principle components of skin and hair, and is secreted by fungi -> sore and itchy skin |
| How does Coagulase work? | Catalyze the formation of blood clot, which serves as a shield for the microbes from being engulfed -> blockage of blood vessel. |
| What is an exotoxins? | A toxin molecule secreted by a living bacterial cell into the infected tissues. |
| Whats the examples of exotoxins? | Haemolysin: disrupt cell membrane of red blood cells e,g, Streptolysin (Streptococcus pyogenes), α and β toxin (Staphylococcus aureus) |
| What is the function of neurotoxin botulinum (Botox)? | Produced by Clostridium botulinum. The toxin prevents the transmission of nerve-muscle stimuli -> muscle paralysis |
| What is an endotoxin? | A toxin that is not actively secreted but shed from the outer membrane. |
| What is the example of endotoxin? | Lipopolysaccharide (LPS), a component of outer membrane of gram negative cell walls. |
| Whats the effect of endotoxin? | Cause fever, inflammation, haemorrhage and diarrhea. |
| What would happen if blood infection by gram-negative bacteria such as E. coli, Salmonella, shigella? | Fatal endotoxic shock |
| What is an excessive or inappropriate host respond? | The capsule of Streptococcus pneumoniae prevents the bacteria from phagocytosis ->continuous influx of fluid into lung space -> Pneumonia |
| What are Superantigens? | It is a bacterial secretion, capable of activating T-Cells at a rate 100 times greater than ordinary antigens -> overwhelming release of cytokines and cell death ->Toxic Shock syndrome |
| What is a mixed infection? | One microbe creates an environment that favours another microbe to invade. Rhinovirus (Primary infection)-> Streptococcus pyogenes(Secondary infection) |
Created by:
kencho
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