Week 3 - Bacterial Pathogenesis and Host Defenses Flashcards
Why is it possible for a small amount of bacteria to have the same damage as a large amount of virus?
Because it is possible for them to produce toxins that can have a ton of damage to the cell
Virulence definition?
Virulence – quantitative measure of pathogenicities measured by the number of bacteria required to cause disease
LD-50 and ID-50? Definition:
LD50 – number of bacteria necessary to kill half the host
ID50 – number of bacteria necessary to cause infection in half the hosts
What are virulence factors?
properties of a bacteria which assist in causing disease ex: pili, capsules, toxins, etc.
What kind of virulence factors are bacterial structures?
- Pili eg. N. gonorrhea to urinary tract epithelium
- Capsules eg. Strep. pneumonia
- Glycocalyx eg. Strep. viridans in heart valves
- Endotoxin eg. Gram negative bacteria
- Biofilms eg. Pseudomonas in cystic fibrosis patients
- Bacterial Secretion Systems eg. T3SS in Salmonella typhimurium
What kinds of secreated virulence factors do bacteria use?
- Collagenase & hyaluronidase eg. Strep. pyogenes cellulitis
- Coagulase eg. Helps coat Staph. aureus with fibrin to help protect from phagocytosis
- Immunoglobulin A protease eg. Degrades IgA allowing Strep. Pneumonia to adhere to mucous membranes
- Leukocidins Destroy neutrophilic leukocytes and macrophages eg. Staphylococci and group A Streptococci
What other kinds of virulence factors do bacteria have?
- M protein - antiphagocytic protein produced by Strep. pyogenes
- Protein A - binds to IgG and prevents activation of complement
- Invasins - bacterial molecules which promote bacterial entry or contact with host cells - eg. Heliobacter pylori
- Outer membrane proteins - produced by Yersinia species to inhibit phagocytosis and cytokine production
- Pathogenicity Islands (PAIs) – code for groups of virulence factors particularly in Gram negatives
What do exotoxins do?
Its a virulence factor that is secreted from bacteria
(A portion is toxic, b portion binds)
They can:
alter cell components, are superantigens, inhibit protein synthesis, increase cAMP synthesis, alter nerve impulses, form pores to mess stuff up
What are the effects of endotoxins, where aer they found?
Part of the polysaccharides found in gram NEGATIVE rod/cocci bacteria (lipid A)
Induce biological effects of FEVER and SHOCK through a few different biological pathways
List a few comonents of innate and acquired immunity:
Innate: macrophages to digest bad stuff up
Acquired: antibodies, cytotoxic t-cells
Passive vs ACitve Immunity
Passive Immunity
Administration of preformed antigen-specific antibodies to help protect from disease ex. Human rabies immune globulin
Active Immunity
Administration of specific antigens to stimulate an individual to develop immunity to help protect from a disease ex. Influenza vaccine
Influenza and diptherai have what kinds of vaccines?
Diptheria - toxoid vaccine
Influenza - has a live version (weakened form) an a whole virus form that is a killed virus
What tricky method does B. recurrentis Neisseria use to avoid acquired immunity?
It actually continuously changes the glycoprotein cassettes expressed on its surface to confuse the host defense
What tricky method does Staphyloccus Aureus use to avoid acquired immunity?
Protein A is factor that can bind immunoglobulins on the bottom side in order to actually look like just another host cell. DISGUISED!
It can also produce coagulase, which allows host firbin to clump on the bacterial surface.
What tricky method does Treponema pallidum use to avoid
It coats itself with host fibronectin
