Bacterial Pathogenesis Flashcards
Name Koch’s postulates and describe what they are
criterial that must be met to prove that a specific microorganism causes a specific disease.
1) microbe must be present in ALL cases of the disease
2) the pathogen can be isolated from the diseased host and grown in pure culture
3) the pathogen from the pure culture causes the disease when inoculated into a healthy, susceptible animal
4) the pathogen can be re-isolated from the new host and shown to be the same as the original pathogen
What is a facultative aerobe?
organism that makes ATP by aerobic respiration when O2 is present but can switch to fermentation or anaerobic respiration if O2 is absent
what is an obligate aerobe
cannot make ATP in the absence of oxygen
What is an obligate anaerobe?
dies in presence of O2
What is an overt/strict pathogen?
only associated with human disease. not found in normal healthy microbial flora
what is an opportunistic pathogen?
present in normal flora but only causes disease when introduced into unprotected sites (e.g. when someone is immunocompromised)
what is a facultative pathogen?
can grow and survive in environment as well as in a host
List 5 bacterial virulence factors
1) adhesins
2) flagella
3) toxins
4) capsule
5) type III secreted molecules (factors secreted by bacterial directly into host cell)
Name as many diseases as you can that can be caused by a Streptococcus pneumoniae infection
pneumonia, septicaemia, meningitis, otitis media (inflammation of the middle ear), sinusitis
What is an endotoxin and what general symptoms does it cause?
part of the outer membrane (LPS) of the cell wall of gram- bacteria. cell bound, heat stable.
Symptoms: fever, diarrhoea, vomiting
what is an exotoxin?
proteins produced extracellularly by certain bacteria. heat unstable, usually highly toxic
What is an enterotoxin
group of exotoxins that act on small intestine. cause change in intestinal permeability leading to diarrhoea
What is a toxoid and what is it used for?
inactivated toxin. used as a vaccine
what bacteria causes botulism and is it gram+ or gram-
Clostridium botulinum. Gr+
List 4 strategies bacteria use to evade the immune system
1) hide
2) antigenic variation and phase variation - changing immunogenicity at a high f to avoid establishing immune response
3) molecular mimicry - decorate outside with molecules similar to host
4) modify or block host immune response
