Part 1 Flashcards
(18 cards)
Example of opportunistic pathogen
Staphylococci - commensals of skin and mucous membranes but pathogens through broken skin.
E.Coli - commensals in Colon but pathogens in urinary tract
How do bacteria cause disease?
Invasion, toxigenicity (production of microbial toxins), immunopathology (host damage from body’s response to infection)
What’s a nosocomial infection?
Hospital acquired
Where is clostridium tetani found?
Faeces and soil- environmental source
Where is the source of streptococcus equi infections?
Another animal (upper respiratory trAct of horses.
What’s an endogenous infection?
When source on body already- commensals
How does Bordatella Bronchiseptica avoid ‘flushing’ action of body fluids?
Sticks to ciliated epithelium in trachea- stops mucociliary escalator moving. End of fimbriae recognise receptors.
What does moraxella bovis cause?
Conjunctivitis of cows.
What are K88 fimbriae, what bacteria has them and why are they important?
E.Coli use them to adhere to mucosal surface of small intestine by K88 receptor binding. Important in clearance- antibody blocks receptor and stops binding.
How to pathogenic bacteria acquire iron?
Siderophores - put out into environment, bind iron and bring back.
Transferin- binding proteins - binds to iron and steals it from other molecules in body
What are siderophores?
Put out into environment to acquire iron.
What’s endotoxin?
Lipopolysaccharide only. Found in gram -ve cell walls
Obligate intracellular pathogens?
Chlamydia, lawsonia
How is antibody mediated opsonophagocytosis avoided?
Molecular mimicry - surface components which appear to be self. Eg. K1 antigen of E.Coli is sialic acid.
Hyaluronic capsule of beta-haemolytic streptococci
Examples of exotoxins produced by gram positive bacteria
Gram positive digest surroundings for nutrition:
Phospholipase, protease, collagenase, hyaluronidase
Clostridial toxins
Tetanus toxin
Botulinum toxin
Leucocidin, haemolysin, antichrmotaxins, C5a protease
Exotoxins produced by gram negative bacteria
Cholera toxins, LT, ST, shiga-like toxin of E. Coli etc
What does endotoxin cause?
LPS- initial fever,
Thrombosis Leucopaenia Compliment activation Hypotension Circulatory collapse Death
How does Mycobacterium in TB cause injury?
Immune-mediated - invade but no known toxin secreted. Tissue destruction and cytokine damage
