POM 11 - Staphylococcus Aureus Flashcards
where does s aureus come from and how has it transmitted
human pathogen that has transmitted to domestic animals
what are the 2 types of nasal carriers for staph aureus
what do they mean and what is their risk of acquiring the disease
persistent carriers = always have staph in their nose = increased risk
persistent non carriers = dont get colonised by staph = low risk
how does staph affect the heart and how is this different from rheumatic fever
in rheumatic fever the antibodies from the immune repsonse cause heart problems
staph binds to heart connective tissue on valve structures and erode through the structures via bacteria - the pumping heart then delivers staph around the body
what happens when staph bacteria is trapped in the hair follicle what is the immune response - 4 stages
bacteria attempt to invade in hair follicle but only some will have ability to interact/bind with/damage human cells
damaged tissue cells release chemicals - cytokines - that recruit immune cells to site via chemotaxis
adjacent capillaries allow WBC diapedesis and move to infection
bacteria ingested by neutrophil and enzymes release chemicals and free radicals to kill bacteria
how does bacteria in hair follicle cause pain and swelling
the cytokines released from the immune response irritate the nerve fibers causing pain and blood flow changes which lead to swelling, warmth and redness
what are the 3 mechanisms that staph aureus has evolved to avoid the human immune system
catalase enzyme
staph protein PVL
CHIPS
how does the catalase enzyme help staph to avoid the human immune system
breaks down the free radicals from the neutrophils to make water
how does the staph protein PVL help staph to avoid the human immune system
destroys WBC
how does CHIPS help staph to avoid the human immune system
stops neutrophils from following chemotaxis gradient
how does staph aureus use protein A to evade the human immune system
protein A binds heavy chain of IgG and masks Staph from the immune system so staph has antibody facing outwards
how does staph aureus use clotting factor to evade the human immune system
staph binds to fibrinogen and coats itself in fibrinogen to escape the immune system
what are the 3 steps of staph treatment
stabilise person
drain pus
antibiotics
how does penicillin treat staph aureus
it inhibits transpeptidase which cross links the peptidoglycan sugars
thus it takes away the structural integrity of the bacterial cell wall and causes the bacteria to explode
what does MRSA stand for
methicillin resistance staph aureus
how has the MRSA Staph strain become resistant
it changed its transpeptidase so that it no longer binds to penicillin
