Catalase POSITIVE, Gram POSITIVE Cocci

Question 1

the most virulent of Staphylococcus

Answer 1

Staphylococcus aureus

Question 2

the 2 staphylococci that produces a polysaccharide capsule to inhibit phagocytosis

Answer 2

S. aureus

S. epidermidis

Question 3

S. aureus causes swelling and exacerbation of tissue damage due to

Answer 3

Protein A

• • bound to cytoplasmic membrane
• • high affinity for Fc receptor of IgG and complement

Question 4

Cytotoxin by S. aureus that is hemotoxic

Answer 4

Alpha toxin

Question 5

Cytotoxin that is a heat-labile sphingomyelinase that catalyzes the hydrolysis of membrane phhospholipids (will result to cell lysis)

Answer 5

Beta toxin

– works hand in hand with Alpha toxin

Question 6

Cytotoxin that is cytolytic to RBCs; demonstrates non-specific membrane toxicity to other mammalian cells

Answer 6

Delta toxin

Question 7

Cytotoxin associated to Panton-Valentine leukocidin (PVL)

Answer 7

Gamma toxin

Question 8

localized skin or soft tissue infections caused by S. aureus

Answer 8

folliculitis, furuncles (boils), carbuncles, impetigo

Question 9

staphylococci that causes Rittter’s disease (aka scalded skin syndrome) usually in neonates

Answer 9

S. aureus

– serine protease

Question 10

staphylococci usually isolated in the urine of sexually active femles

Answer 10

S. saprophyticus

Question 11

the strain of S. aures that is knon to produce the Panton Valentine Leukocidin toxin (PVL toxin)

Answer 11

MRSA

– methicillin resistant Staphylococcus aureus

Question 12

common diseases caused by S. aureus

Answer 12

Toxic Shock Syndrome: caused by TSST-1 aka PYROGENIC EXOTOXIN C

Ritter’s Disease: Scalded skin syndrome; usually affects neonates

Question 13

most common coagulase-negative staphyloccci

Answer 13

S. epidermidis

Question 14

microscopic arrangement of Staphylococcus

Answer 14

gram-positive cocci in clusters

Question 15

gene that encodes for methicillin resistance in S. aureus

Answer 15

mecA gene

Question 16

SELECTIVE media for Staphylococci

INCUBATION: 48 to 72 hours

Answer 16

PhenylEthyl Alcohol (PEA)
Columbia colistin-nalidixic acid (CNA)

— eliminates contamination by gram negative organisms in heavily contaminated specimens like feces

Manitol Salt Agar (MSA)
— 10% salt, sugar mannitol and phenol red (will turn yellow in the presence of staph bc it will ferment manitol to acidic pH)

Question 17

selective and differential medium for MRSA

Answer 17

CHROMAgar

– contains CEFOXITIN; MRSA is RESISTANT to cefoxitin; grow MAUVE colonies

Question 18

incubation conditions of Staphylococcus

Answer 18

ambient– 35C in carbon dioxide for 24 hrs

5% blood agar medium or CAM

Question 19

test that will differentiate Micrococcus spp. and Staphylcoccus spp.

Answer 19

Micrdase test

– Mirococcus will turn blue in 2 minutes