staphylococcus- Daniels Flashcards
general overview of staphylococcus
Gram + cocci
- Non-motile
- Non-spore forming
- Predominantly facultative anaerobes
Basic phenotype of staphylococcus pneumoniae
1) Gram positive cocci
2) positive catalase test
3) ability to grow in 7.5% NaCl
The coagulase test
A) add bacteria to rabbit plasma
B) Differentiates S. aureus and 6 other species
(S. aureus causes the highest burden of disease in people)
T/F- coagulase negative staph are of considerable concern for humans
FALSE- only coagulase positive staph pose a serious threat
CoNS= coagulase negative staph
infections caused by S. aureus
1) Integumentary and wounds
2) Bacteremia - internal infections
3) Aspiration pneumonia
4) UTI
5) Toxic shock syndrome
6) scalded skin syndrome
Encounter
-Live on and around people
- Skin, mucosal surfaces
- Usually behave commensally
(Opportunistic in right conditions)
Entry of staph
Damage to skin/follicles
- Wounds
- Burns
- Insect bites
Damage to mucosal surface
multiplication/spread
Variable with
1) Bacterial inoculum (more is worse)
2) Host immunocompetence
3) Location of infection
Bacteremia + immune compromise = trouble
Populations at elevated risk for severe infections from staphylococcus
Young children/Elderly Diabetics Individuals on immunosuppressive therapy HIV+ Dialysis patients IV drug users
Factors that enhance the ability to colonize and invade
MSCRAMMs = Microbial Surface Components Recognizing Adhesive Matrix Molecules”
1) Fibronectin binding proteins (FnbpA and FnbpB)
2) Collagen binding protein (CNA)
3) Clumping factors bind fibrinogen
Clumping factors that bind fibrinogen are key in the pathogenesis of what?
bacterial endocarditis
Acute suppurative inflammation =
accumulation of pus
Pus = neutrophils (a.k.a Polymorphonuclear WBCs or “PMNs”)
the formation of Abscesses
1) WBCs :The first ones to show up
2) Phagocytosis of foreign invaders
3) release ROS- reactive oxygen species
4) Release signaling molecules to call more WBCs to the area (cytokines)
what is the effect of the Polysaccharide capsule
blocks phagocytosis
what does Protein A block?
blocks antibody function
Panton-Valentine Leukocidin
a potent cytotoxin. acts as beta-pore-forming toxin.
very effective against PMN’s (neutrophils)
SSSS – Staphylcoccal Scalded Skin Syndrome
caused by release of exfoliative toxins A and B
toxins cause the outer layers of epidermis to separate
what is TSST-1?
A) its a Superantigen
B) cause an unregulated inflammatory response by activating high #s of CD4+ T cells
C) Cross link T-cell receptor with the MHC-II surface molecule of antigen presenting cells
what type of molecules cause toxic shock syndrome?
Cytokines
TSS= “cytokine storm”
what effect does IL-1 have on the body?
fever
what does a large amount of TNF-alpha and beta cause?
Hypotension, leaky capillaries
what do IFN-gamma and IL-2 causes?
Rash
Staphylococcal Food Poisoning
A) Toxin is pre-formed in contaminated food
B) Not an INFECTION –> INTOXICATION
C) Enterotoxins A,B,C,D,E
D) Superantigens, Cause intense peristalsis
HEAT STABLE TOXINS
what category of drugs are effective against staph
beta-lactam’s –> break up peptidoglycan layer
what are the 2 penicillin binding proteins?
Transpeptidases and transglycosylases
β-lactam antimicrobial agents are inhibitory substrates for what?
Penicillin binding proteins
what extra protein does MRSA contain?
PBP2a
why is MRSA a serious concern?
normal beta-lactam drugs are not effective against it
what drug is used to treat MRSA?
Vancomycin
what is Vancomycin?
A glycopeptide class antimicrobial drug
what are the colonization site for MRSA?
Axilla, groin and Nares
