Microbiology (Gram positives)

Question 1

Staphlococcus aureus:

1. G+ or G-?
2. is it normally on body?
3. is it normally found in wounds?
4. Catalase+ or catalase-?
5. Coagulase+ or coagulase-?
6. What are its virulence factors?

Answer 1

1. Gram positive cocci, grape-like clusters
2. Yes, normally colonizes external nares and skin
3. Yes, normally found in wounds
4. Catalase positive
5. Coagulase positive (distinguishes it from other staphylococci such as Staph epidermidis, grows yellowish-cream colored on blood agar instead of clear/white of coagulase negative Staphs)
6. Protein A (binds to constant region (Fc) of IgG Ab, preventing Ag binding, which means it’s invisible to the immune system), capsule to avoid phagocytosis, fibronectin binding protein and receptors for Type IV collagen lets bacteria adhere to CT including joints, Antibiotic resistance bc of beta-lactmase enzyme (penicillin) or penicillin binding protein (methicillin and vancomycin).

Question 2

Streptococcus agalactiae (Group B strep):

1. G+ or G-?
2. How do infants get osteomyelitis from it?
3. virulence factors
4. What type of hemolysis on blood agar?
5. What Lancefield System group?
6. catalase+ or catalase-?
7. other facts

Answer 2

1. Gram positive cocci in chains
2. vaginal birth, get it from mom
3. anti-phagocytic capsule (inefficient phagocytosis bc little opsonization
4. Beta hemolytic
5. Group B
6. Catalase negative
7. Beta hemolysis, hydrolyzes hippurate, bacitracin resistant (discs on agar, group B so can grow)

Question 3

What are the three types of hemolysis?

Answer 3

Alpha= partial hemolysis
Beta= complete hemolysis
Gamma= no hemolysis

Question 4

Streptococcus pyogenes (group A strep):

1. leads to what?
2. Virulence factor
3. what type of hemolysis?
4. Is it normally found in human body? if so, where?

Answer 4

1. osteomyelitis in CHILDREN
2. capsule
3. Beta hemolytic
4. yes, normal flora of respiratory tract

Question 5

Streptococcus viridans:

1. What type of hemolysis?

Answer 5

not an actual species name, but written like that (pseudo-taxonomic term)
1. Alpha hemolysis, usually commensals

Question 6

Streptococcus pneumoniae:

1. what form is it in?
2. virulence factor:
3. what type of hemolysis?

Answer 6

1. diplococci or short chains
2. bigger capsule
3. Alpha hemolytic

Question 7

Enterococcus species (formerly Group D Strep):

1. Gram+ or gram-?
2. virulence factor

Answer 7

1. Gram+ cocci

2. antibiotic resistance is common (treatment implications)