Lecture 51 - Gram + Pyogenic Cocci (Staphylococci)

Question 1

A good way to differentiate between Staph and Strep is morphologically. _______ appears as clusters of cocci, while _______ appears as pairs or chains of cocci. Also, you can use a ______ test, because ______ produce it and ______ do not. The reaction with this enzyme and H2O2 produces bubbles.

Answer 1

Staph

Strep

Catalase

Staph

Strep

Question 2

Staph can grow in high _____ media and are resistant to drying/heat as well as many antibiotics.

Answer 2

high Salt (7.5% NaCl)

Question 3

Staph aureus typically causes skin infections, ______, toxic shock syndrome, and _____ poisoning.

Staph epidermidis typically causes septicemia and ______ (usually results from implanted device).

Staph saprophyticus typically causes _____ _____ infections.

Answer 3

Osteomyelitis

Food poisoning

Endocarditis

Urinary tract

Question 4

Staph _____ produces coagulase, while the other two Staphs do not. This is another good way to differentiate. It also produces Staphyloxanthin, a caretinoid which is an antioxidant that helps it defend against ROS. Given that it’s a caretinoid, what color might the colonies appear when plated?

Answer 4

Aureus

The colonies would appear Golden –> “Golden Staph”

Question 5

When Staph _____ is plated with blood, it will appear with a zone of clearing around the colonies due to Beta-hemolysis carried out by its ___ toxin.

Answer 5

Staph aureus

Alpha toxin

Question 6

Staph Aureus produces Clumping factor that binds ______ and promotes aggregation of the bacteria (hence “Clumping” factor”) and Protein ___ that is linked to peptidoglycan and binds the ____ region of IgG.

What do these two things help Staph aureus avoid?

Answer 6

Fibrinogen

Protein A

Fc

Clumping factor and Protein A both help Staph aureus avoid Phagocytosis.

Question 7

Staph aureus also produces _______, which is the enzyme responsible for degrading the class of drugs penicillin belongs to, inducing resistance to them.

Answer 7

Beta-lactamase

Question 8

Staph aureus produces a desmosomal ______ (an A-B toxin) that can lead to Scalded skin syndrome in young children (usually < 4 years old). Keep in mind this syndrome results from the toxin, NOT an infection!

Answer 8

Protease

Question 9

Staph aureus produces an _______ that causes food poisoning. Keep in mind this toxin-induced food poisoning occurs rapidly, between ___ to ____ hrs after ingestion –> this is a good way to distinguish it from an infection-induced food poisoning.

Answer 9

Enterotoxin

1 to 6 hrs

Question 10

A way to distinguish between Staph epidermidis and saprophyticus is via treatment with ______. Staph saprophyticus is inherently resistant.

Answer 10

Novobiocin

Question 11

Staph epidermidis colonies form biofilms and are difficult to treat. They should be treated with ______ (last line for Staph aureus).

Answer 11

Vancomycin

Question 12

Staph saprophyticus should be treated with _______-sulfamethoxazole.

Answer 12

Trimethoprim-Sulfamethoxazole.