Section 2 GRAM POSITIVE COCCI

Question 1

What are the leading cause of infections?

Answer 1

Staphylococci

Question 2

Where are Staphylococci found?

Answer 2

Part of normal flora

Question 3

What do the Staphylococci on the skin do?

Answer 3

• Function as competitors to prevent pathogens from colonizing skin
• Produce antimicrobial substances that are active against other G+

Question 4

Is the normal flora in the GI in higher number in the upper or lower intestine?

Answer 4

In higher numbers in lower intestine, due to flushing of gastric juices through
upper intestine

Question 5

Which exotoxin is the most potent membrane damaging toxin?

Answer 5

Alpha (α) toxin

Question 6

Which toxin is a sphingomyelinase which damages membranes rich in lipids?

Answer 6

Beta (β) toxin

Question 7

Which toxin lyses erythrocytes (RBCs)

Answer 7

Gamma toxin (γ)

Question 8

Which exotoxin destroys leukocytes (WBCs)

Answer 8

Leukocidins

*Causes release and rupture of lysosomes (contain hydrolytic enzymes) resulting in further tissue damage

Question 9

What is a Toxic Shock Syndrome Toxin (TSST) and what does it do?

Answer 9

A superantigen causing massive release of cytokines which cause a drop in blood pressure and kidney failure

• Powerful exotoxin that stimulates tumor necrosis factor (TNF) leading to necrosis
• Also stimulates interleukin leading to fever, rash
• Originally associated with tampon use, also affects men and non-menstruating women

Question 10

What is the name for Exotoxins that destroy material the binds together the layers of skin?

Answer 10

Exfoliatin

Question 11

Which toxin is being described?
“Unlike most exotoxins S. aureus enterotoxin is heat-stable, cooking food will not destroy it
-If present in food when consumed causes nausea and vomiting”

Answer 11

Enterotoxin

Question 12

Which extracellular enzyme breaks down proteoglycans in connective tissue?

Answer 12

Hyaluronidase

Question 13

What is the extracellular enzyme that converts hydrogen peroxide to oxygen and water?

Answer 13

Catalase

Question 14

Which extracellular enzyme reacts with prothrombin in blood resulting in
staphylothrombin causing blood to clot?

Answer 14

Coagulase

Question 15

Which extracellular enzyme lyses clots?

Answer 15

Fibrinolysin

Question 16

What are the characteristics of Staphylococcus aureus?

Answer 16

*Mannitol fermentation = Golden pigment
(only staph aureus can ferment mannitol)
*Coagulase positive

Question 17

What are some of the pathogenesis of Staphylococcus aureus?

Answer 17

Osteomyelitis (bone infection)
Toxic shock syndrome
Wound infections
Enteritis
Catheter and shunt infections
Furuncles and carbuncles
Impetigo
Folliculitis
Scalded skin syndrome

Question 18

What type of Staphylococcus aureus occurs following a long course of antibiotics or following surgery?

Answer 18

MRSA (methicillin resistant S. aureus

Question 19

Are staph epidermidis and staph saprolyticus coagulase positive or negative?

Answer 19

Negative

Question 20

Which type of staphylococcus is a leading cause of UTI’s?

Answer 20

Staph saprolyticus

Question 21

What are the differences/similarities in Staphylococcus sp. and Streptococcus sp. as far as lab diagnosis?

Answer 21

Both are Gram positive cocci

• Catalase test
• Staphylococcus sp. is positive
• Streptococcus sp. is negative

Question 22

Are Streptococci gram positive or negative?
What is streptococci’s shape?
Are they motile or non-motile
Are they endospore or non-endospore forming?

Answer 22

Gram positive
Spherical shape - cocci
Non-motile
Non-endospore forming

Question 23

What are used to type Streptococci?

Answer 23

Hemolysins

Question 24

Which hemolysin (used to classify streptococci) is a partial hemolysis with greenish cast around colonies?

Answer 24

α-hemolysis

Question 25

Which hemolysin (used to classify streptococci) is a complete lysis of blood cells creating clear area around colonies?

Answer 25

β-hemolysis

Question 26

Which hemolysin (used to classify streptococci) has no lysis of blood cells?

Answer 26

γ-hemolysis

Question 27

Which serological testing proposed by Rebecca Lancefield for establishing classification of streptococci includes Enterococcus faecalis, abscess, UTI, endocarditis?

Answer 27

Group D

Question 28

Which serological testing proposed by Rebecca Lancefield for establishing classification of streptococci are found colonizing the female genital tract and can cause infection in newborn, neonatal sepsis, and meningitis?

Answer 28

Group B