staphylococcus aureus Flashcards
Staph aureus is coagulase? and catalase?
catalase and coagulase +
how do colonies of stap aureus look like?
yellow colonies in mannitol salt agar
Staph aureus can tolerate high concentration of what substance?
salt
where does stap aureus ferment?
in mannitol
Staph aureus is resistant to what?
1) penicillin
2) methicillin
3) vancomycin
why is stap aureus resistant to penicillin?
it has penicillinase
what is used for treatment when there is resistance to penicillin?
oxacillin
why is staph aureus resistant to methicillin (MRSA)?
it modifies PBP which has low affinity for beta lactam drugs
how do you treat methicillin resistant staph aureus?
vancomycin
how does staph aureus become resistant to vancomycin (VRSA)?
converts D-Ala-D-Ala to D-Ala-D-Lac
what is used to treat VRSA?
quinupristin and dalfopristin
what illnesses are related to toxins from staph aureus? (3)
staph scalded skin syndrome = exfoliate toxin
food poisoning = enterotoxin
Toxic Shock Syndrome = TSST-1
what enzymes does staph aureus produce?
catalase
coagulase
protein A
cytolytic toxins
enterotoxins
exfoliative
toxic shock syndrome toxin-1 (TSST-1)
what is toxic shock syndrome toxin-1?
what is its onset?
what symptoms are seen?
it is a superantigen where there is non-specific activation of T lymphocytes and consequent release of a large number of cytokines
it has an acute onset
fever, hypotension, multiple system organ failure
what do the exfoliative enzymes of staph aureus cause?
what is seen with this?
what age must people have for this to happen?
what is a complication that can happen with the disease caused by exfoliative enzymes of staph aureus?
Staph scalded skin syndrome (SSSS),
A-B toxin targets epithelial cells and breaks it (targets tight junctions and desmosomes)
on children 6 or below
bullous impetigo (localized SSSS), will have impetigo but with fever
what will cytolytic toxins do?
will destroy cell membranes
what will protein A do?
inhibit phagocytosis by binding to Fc portion
what will coagulase secreted by staph aureus cause?
abcesses
what will secreted enterotoxins by staph aureus cause?
what time does it take to incubate? how long until it resolves?
what foods can have staph aureus secreting enterotoxins
food poisoning (nausea, vomit, no poop)
incubation: 2-6 hrs
resolves: 24 hrs
foods: potato salad, custards, ham, ice cream
what infections or diseases can be caused by staph aureus?
1) skin lesions
2) acute endocarditis
3) osteomyelitis
4) septic arthritis
5) pneumonia
6) nococomial infections
what skin infections are caused by staph aureus?
abcesses, folliculitis, impetigo-> (superficial skin infections in kids)
how does staph aureus cause acute endocarditis?
who is most at risk?
what part of the heart is most at risk with acute endocarditis?
by being prolonged to staph bacteremia
IV drug users
tricuspid valve
what is the most common cause of septic shock in children and young adults?
staph aureus
what is the most common cause of septic shock in sexually active individuals?
Nisseria gonorrhea
what will osteomyelitis from staph aureus cause in adults?
flat bones
what will osteomyelitis from staph aureus cause in children?
affect elongation of long bones
what is the most common cause of osteomyelitis in people with sickle cell or thalassemia?
salmonella
what is the most common cause of osteomyelitis?
staph aureus
who gets pneumonia due to staph aureus?
predisposed people with diseases like: CGD (chronic granulomatous disease), CF (C. Fibrosis)
if a patient has lobular pneumonia due to staph aureus, what will there be a high rate of?
abcess formation
for Toxic shock syndrome, a blood culture will be + or -?
negative
how do you distinguish between bullous impetigo and staph scalded syndrome?
bullae from impetigo will have the bacteria as staph scalded s. will not have the bacteria present in lesions
