Mechanisms of Infections Flashcards
What is normal flora?
Organisms that are found typically at specific body sites
What is skin flora?
It is generally colonized by gram positive bacteria, both bacilli and cocci
How does the genitourinary tract work?
The urine washes organisms from the urethra to maintain a sterile bladder
The vaginal flora changes with age (puberty means women get colonized by lactobacillus which drops pH to acidic) Sperm is basic and dies
Perturbing the normal flora
Normal flora usually provides protection against potential pathogens.
Antibiotics can wipe out all normal flora, which can cause a bacteria like C. diff to colonize the gut
What is C difficile?
Leading cause of antibiotic associated diarheaa
Associated with changes to GI tract
Can lead to death
What is a non specific host defence
They don’t specifically target something they just do
Like peeing-cleans out bladder
This could be enzymes and pH of the environment (stomach pH)
Cough reflex
What are some specific examples of non-specific host responses?
Urination-washes organisms out of
Muccocilary elevator-cough removes cells
Lysozyme-frees iron
Secretaory IgA-antibody secretions
Inflammation-toxic to cells
What are the 3 lines of defence in the body
1st-barriers at body surfaces-skin + muccous
2ns-inflammation + fever
Both these are non specific
Then 3rd is aquired-T cells, antibodies
What is biofilm?
Forms when an organism sticks to a surface and produces an extracellular matrix
Antibiotics can’t get into the biofilm
How does bacteria avoid phagocytosis?
A capsule (thick polysaccarharide layer), its like a shield (macrophage can’t kill it)
What does toxin production do?
Toxins destroy immune response so bacteria remains protected
What are the 2 types of toxins?
Endotoxin-structural component of gram negative bacteria
Exotoxin-excreted toxins
