Staph Skin disease Checkpoint

Question 1

I. In the lab, how are S. aureus, epidermidis, and haemolyticus ID?

Answer 1

I. S. aureus is gram post coag pos gold agar, mannitol salt agar
II. Epidermidis- gamma hemolytic, coag neg
III. Haemolyticus- beta hemolytic, coag neg

Question 2

II. Where are the staphylococci commonly found?

Answer 2

I. Anterior nares

Question 3

III. What types of infections are S. epidermidis and haemolyticus commonly associated with?

Answer 3

I. Epidermidis- foreign body colonization (shunts, catheters, joint prostheses)
II. Haemolyticus- similar to epidermidis, both have biofilms

Question 4

IV. Which bacteria is the most common cause of false positive in patient blood samples?

Answer 4

I. S. epidermidis

Question 5

V. What is the major virulence factor used by S. epidermidis and haemolyticus and how does it help the bacteria avoid the host immune response?

Answer 5

I. Biofilm formation and secreting extracellular polysaccharides (glycocalyx)

Question 6

VI. Why are TLRs important in the early modulation of the innate immune response? Which type of ligands do they detect in general?

Answer 6

I. Major surface antigen to start off immune response, techoic acid

Question 7

VII. What is the mechanism of protein A?

Answer 7

I. Interferes with opsonizationand complement activation

II. Antibody binds fc portion to protein A

Question 8

VIII. What is the function of Panton-Valentine leukocidin and how do strains of S. aureus obtain this virulence factor?

Answer 8

I. Kills PMN and macrophages only, channel forming, bacteriophage

Question 9

IX. Which bacteria causes bullous impetigo? Do all strain of this bacteria cause this disease?

Answer 9

I. Staph aureus, no can do non-bullae as well

Question 10

X. What is the mechanism of TSST-1 and what are the clinical manifestations?

Answer 10

I. Super antigen

I. Fever; rash, desquamation, hypotension, multisystem involvement (3 or more)

Question 11

XI. Which two diseases are associated with exfoliative toxin-producing strains of S. aureus?

Answer 11

I. Impetigo, ritter’s disease

Question 12

XII. What are the symptoms of scalded skin syndrome?

Answer 12

I. Rash on extremities, then desquamation