Staphylococci

Question 1

Protein A

Answer 1

Major protein in cell wall. Binds to Fc portion of IgG at complement binding site and prevents complement activation; no C3b produced so phagocytosis of organisms is greatly reduced

Question 2

Mediate adherence of staph to mucosal cells

Answer 2

Teichoic acids

Question 3

induces IL-1 and TNF from macrophages

Answer 3

Lipotechoic acid

Question 4

Stimulates macrophages to produce cytokines, activates complement/coagulation cascades

Answer 4

Peptidoglycan

Question 5

Forms holes in host cells

Causes necrosis of skin and hemolysis

Answer 5

alphatoxin/hemolysin

Question 6

Enhances pathogenicity by inactivating microbicidal effect of superoxides and other reactive oxygen species within neutrophils

Answer 6

Staphyloxanthin

Question 7

Causes plasma to clot by activating prothrombin to form thrombin which catalyzes activation of fibrinogen to form fibrin clot
Serves to wall off infected site, delaying migration of neutrophils to the site

Answer 7

Coagulase

Question 8

How can Staphylococcus aureus be distinguished from other staphylococci in the lab?

Answer 8

S. aureus produces coagulase and beta hemolysis

Question 9

Cell content leak out of a pore which the toxin forms
Causes severe skin/soft tissue infections as well as severe necrotizing pneumonia
Produced by MRSA strains, typically community-acquired

Answer 9

Panton Valentine (P-V) leukocidin

Question 10

Lyses phagocytes/RBCs

Answer 10

Gamma-toxin/leukotoxin (membrane-damaging hemolytic toxin)

Question 11

Acts as a protease that cleaves desmoglein in desmosomes, leading to separation of epidermis at the granular cell layer

Answer 11

Exfoliatin/Exfoliative toxins A and B - scalded skin syndrom

Question 12

causes prominent vomiting and watery, non-bloody diarrhea. Acts as superantigen in GI tract, stimulates IL-1 and IL-2 from macrophages and helper T cells.

Answer 12

Enterotoxin A

Question 13

Stimulates release of large amounts of IL-1, IL-2, and TNF.

Answer 13

TSST from S. Aureus - blood cultures negative

Question 14

Fever
Hypotension
Dizziness/syncope
Diffuse macular erythroderma that desquamates 1-2 weeks after onset
Vomiting/diarrhea
Severe myalgias with CPK elevation
Renal failure
Transaminitis or hyperbilirubinemia
Thrombocytopenia

Answer 14

Toxic Shock Syndrome

Question 15

What are some treatment options for MRSA infection?

Answer 15

Vancomycin
Ceftaroline
Linezolid

Question 16

Resistance mechanism of MRSA?

Answer 16

Changes in PBP in their cell membranes. MecA genes on the bacterial chromosome encode these altered PBPs

Question 17

Resistance mechanism of VRSA?

Answer 17

Genes encode enzymes that substitute D-lactate for D-alanine in the peptidoglycan

Question 18

Tx TSS

Answer 18

Vanc/Oxacillin (MRSA/MSSA) PLUS Clindamycin

Question 19

Intranasal mupirocin to reduce colonization, combined with Hibiclens (chlorhexidine gluconate) for bathing +/- antibiotics (Doxy, Bactrim)

Answer 19

Staph Aureus prevention

Question 20

Catalase positive, coagulase negative, non-hemolytic, urease positive, does not ferment mannitol, novobiocin resistant

Answer 20

Staph saprophyticus

Question 21

Catalase positive, coagulase negative, non-hemolytic, urease positive, does not ferment mannitol, novobiocin sensitive

Answer 21

Staph Epi

Question 22

Catalase positive, coagulase positive, beta hemolytic, ferments mannitol

Answer 22

Staph Aureus

Question 23

bubbles

Answer 23

catalase positive

Question 24

Staph Epi Tx

Answer 24

Vancomycin (if MSSE, can use oxacillin/nafcillin). Rifampin or Gent should be added for prosthetic valve endocarditis. Remove the device if possible

Question 25

Staph Sapro UTI tx

Answer 25

Bactrim or Cipro