Staph Flashcards
What is the gram stain of staph?
Gm + clusters
What pattern of hemolysis does Staph show?
B hemolysis
Why is it called Staph aureus?
-grows yellow on culture Aureus = gold
Is S. aureus coagulase positive or negative?
Positive
What are the three layers of the staph capsule?
-microcapsule -capsule -slime (most external)
What layer of the staph capsule is used to serotype them?
-microcapsule
What are microbial surface components recognizing adhesive matrix molecules? (MSCRAMMS)
-structural features on staph held in common between surface proteins
What is protein A in staph?
-incorporated covalently into outer peptidoglycan layer -binds to Fc component of antibodies, except IgG3 -Antiphagocytic
What does coagulase do?
-interacts with fibrinogen D fragment to produce clumping, protects from phagocytosis -used in diagnostic tests to discriminate between S. aureus (+) and coagulase (-) staph in clinical specimens
What toxins are produced by staph?
-alpha, beta, gamma, and delta hemolysin toxins -Enterotoxins A, B, C1-2, D & E -Toxic Shock Syndrome Toxin I (TSST-1) -exofoliatins
What do alpha, beta, gamma, and delta toxins of staph do?
disrupt cell membranes =hemolysin -destroy RBCs, PMNs, and platelets
What are exofoliatins produced by staph do?
-scalded skin syndrome -act on stratum granulosum to produce rash, blisters, & exfoliation -act as superantigens
What do Enterotoxins A, B, C1-2, D & E produced by staph do?
-food poisoning -vomiting
What does Toxic Shock Syndrome Toxin I (TSST-1): produced by staph do?
-Superantigen that causes clonal expansion of resting T-cells & results in massive cytokine release
Who is at greater risk for staph colonization?
-Needle users -skin breaks -diabetics injecting insulin -allergy patients -dialysis -IV drug users
What are Clinical Clues That May Help Determine if a S. aureus Bacteremia is Due to a Complicated Infection and/or Endocarditis?
Younger patient without underlying illnesses; -Community-acquired (e.g., illicit drugs); -No recognizable primary infections; -Skin evidence of systemic infection; -(+) echocardiogram (Transesophageal Echo); -Failure to defervesce (fever break) by 72 hours on therapy; -(+) blood cultures at 48-96 hours on therapy.
What is Staphylococcal Scalded Skin Syndrome?
Characterized by the appearance of large bullae & separation of large areas of the epidermis due to effects of the exfoliatin toxin at the stratum granulosum level of the skin. -more common in newborns
Which of the following individuals is most likely to be chronically colonized with Staphylococcus aureus? a. Allergy patient taking Benadryl b. Diabetic on oral metformin/glipizide c. Hemodialysis patient d. Drug addict that snorts cocaine
c. Hemodialysis patient
A 35-year-old woman who is menstruating presented to the ER with hypotension and the following physical findings: -strawberry tongue -conjunctivitss -blanching rash What toxin is responsible for this? a. TSST-1 b. Panton-Valentine leukocidin c. Enterotoxin C1 d. delta toxin
a. TSST-1
What is true about antibiotic therapy in this woman with toxic shock syndrome? a. Because it is a toxin-induced disorder, caused by colonization and not infection, antibiotics are not beneficial. b. Appropriate antibiotic therapy should be provided in order to attempt to prevent recurrent episodes. c. Antibiotic therapy should not be provided because it may prevent the development of an appropriate humoral immune response. d. Both a & c.
b. Appropriate antibiotic therapy should be provided in order to attempt to prevent recurrent episodes