Session 7: Pathogenicity Flashcards
Opportunistic pathogens
A microorganism that may cause disease if given right circumstances
Primary pathogens
Cause diseases in healthy immunocompetent individuals.
Virulence
A measure of the amount to which the microorganism is pathogenic
Virulence factor
Something that helps the virus (ex: a capsule)
Portal of entry
Chlamydia and mucous membrane
Salmonella and GI system
Tropism (type of cell they infect)
Influenza virus and respiratory epithelium with sialic acid
E. coli and urinary tract epithelium with D mannuse residues
Microbes that produce toxins that get into cells
Corynebacterium diphtheriae ( icky membrane in the back of throat and suck down into lungs)
Cholerae, pertussis
Skin as portal of entry
One of the largest organs in body (SA)
- few organism can breach the intact skin (hookworms)
- most organisms need a break in skin to enter (S. Pyogenes-flesh eating)
- some bacteria enter through sweat and hair follicles and skin (scenes and aureus)
Adherence
1st step towards establishment of infection, organism gets a foothold
- penetration of cell walls/membranes occurs
- facilitated by adhesions or ligands and receptor that bind and recognize structures.
- include lipoprotein and glycoproteins
N. Gonorrhoae
Pilli or fimbriae contain adhesions
S. Mutons
Glycocalyx
Capsules
Glycocalyx- presents C3b from binding and the phagocyte from recognizing and ingesting the Bacteria. Also aids in adherence to host cells. Antibiotics produced in the capsule enables phagocytes to ingest organism.
Ex: pneumonioe, ecoli, gonorrhoea
M. Protein: streptococcus pyogenes
Heat and acid resistant protein in cell wall that allows attachment of bacteria to epithelial cells and inhibits phagocytosis
Mycolic acids
Tuberculosis
-waxy substance in cell walls make the bacterium resistant to digestion, inside the phagocyte
Fc receptors
With Fc receptors in cell wall, then it binds the Fc area of the antibody
-prevents macrophages from biding due to the inability to bind to Fab area
Bacteria without Fc receptor in cell wall is….
Phagocytosis happens
Exoenyzmes
released from bacterial cells
- Leucocldin: destroys blood cells ( S. aureus)
- Kinase: break down fibrin and dissolve clots, forms by body to isolate infection
- Hemolysin: breaks down RBC (includes staph, strep, listeria)
Coagulase
clots; coverts fibrinogen (soluble) to fibrin ( insoluble). Clot can wall off from the host defenses: convert real protein strands that cause the clot
collagenase
breaks down collagen, connective tissues (clostridium)
Lecithinase
destroys plasma membranes
proteases
inactivates antibodies and other body proteins ( breaks down proteins), IgA
coagulase test
- take rabbit plasma ( contains all the blood clotting proteins that haven’t been activated yet) and bacteria
- incubate it
- Positive means clot, fibrin is solid (coagulase produced aureus)
Negative means no clot, no fibrin, liquid (epidermis)