Chapter 5: Gram-positive Bacteria: Staphylococci Flashcards
Staphylococci - Gram stain?
Gram-positive
What are the 3 major pathogenic species of staphylococci?
1) S. aureus
2) S. epidermidis
3) S. saprophyticus
Staphylococci - morphology?
grape-like clusters of cocci
Staphylococci - catalase?
catalase-positive
all staph are catalase positive
Staphylococcus aureus displays what pattern of hemolysis when grown on blood agar?
beta-hemolytic
forms golden pigment on blood agar
How can Staphylococcus aureus be differentiated from other beta-hemolytic cocci?
S. aureus forms a yellow gold pigment on sheep blood agar (aurei = golden)
What beta hemolytic cocci forms yellow gold colonies on blood agar?
Staphylococcus aureus
Staphylococcus aureus - coagulase?
coagulase-positive
Which staphylococci species are coagulase positive?
Staph aureus
Which staphylococci species are coagulase negative?
S. epidermidis or S. saprophyticus
How can Gram-positive cocci be differentiated from each other?
catalase: Staphylococci are positive; Streptococci are negative
How can staphylococci species be differentiated from each other?
S. aureus is coagulase positive; S. epidermidis and S. saprophyticus are coagulase negative
What virulence factors (protective proteins) does Staphylococcus aureus express? (5)
1) Protein A
2) Coagulase
3) Hemolysins
4) Leukocidins
5) Penicillinase
What is the major virulence factor for Staphylococcus aureus?
Protein A
binds the Fc region of IgG to prevent opsonizatin/phagocytosis and complement fixation
What is Protein A?
binds the Fc portion of IgG to prevent opsonization/phagocytosis and complement fixation
(major virulence factor for Staphylococcus aureus)
What protein binds the Fc portion of IgG to prevent opsonization/phagocytosis and complement fixation?
(major virulence factor for Staphylococcus aureus)
Protein A
Protein A is a major virulence factor for which organism?
Staphylococcus aureus
What is coagulase?
enzyme which activates prothrombin to thrombin, causing blood to clot
What enzyme which activates prothrombin to thrombin, causing blood to clot?
(major virulence factor for S. aureus)
coagulase
How does coagulase act as a virulence factor for Staphylococcus aureus?
coagulase, by activating prothrombin, leads to fibrin formation around the bacteria, protecting it from phagocytosis
What are hemolysins?
enzymes expressed by Staphylococcus aureus that destroy RBCs, neutrophils, macrophages, and platelets. alpha, beta, gamma, and delta types.
What enzymes expressed by Staphylococcus aureus destroy RBCs, neutrophils, macrophages, and platelets; and have alpha, beta, gamma, and delta types?
hemolysins
What are leukocidins?
cytotoxin that destroys leukocytes (WBCs), expressed by S. aureus
What are cytotoxins that destroy leukocytes (WBCs), expressed by S. aureus?
leukocidins
Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) produces which particular leukocidin?
Panton-Velentine Leukocidin (PVL)
Panton-Valentine Leukocidin (PVL) is produced by which microbe?
CA-MRSA: community-acquired methicillin resistant Stapylococcus aureus
What is penicillinase?
secreted form of beta-lactamase, which disrupts the beta-lactam portion of the penicillin molecule, thereby inactivating the antibiotic
What enzyme is essentially a secreted form of beta-lactamase, which disrupts the beta-lactam portion of the penicillin molecule, thereby inactivating the antibiotic?
penicillinase
What virulence factors (tissue-destroying proteins) does Staphylococcus aureus produce? (3)
1) Hyaluronidase
2) Staphylokinase
3) Lipase
What is staphylokinase?
expressed by S. aureus, activates plasmin to break up fibrin clots (like streptokinase)
What enzyme, expressed by S. aureus, activates plasmin to break up fibrin clots?
staphylokinase
How is lipase a virulence factor for S. aureus?
Lipase degrades fats and oils, which often accumulate on the surface of our body. This degradation facilitates S. aureus’ colonization of sebaceous glands.
What is hyaluronidase?
breaks down proteoglycans of extracellular matrix. Expressed by Group A strep (S. pyogenes) and S. aureus
What protein breaks down proteoglycans of extracellular matrix, and is expressed by Group A strep (S. pyogenes) and S. aureus?
hyaluronidase
What superantigen produced by Staphylococcus aureus causes shock?
Toxic shock syndrome toxin (TSST-1)