Staph and Strep

Question 1

Gram\_\_\_\_
Shape?
Motile?
oxidative respiration?
Salt tolerant?

Answer 1

gram positive 
cocci (round), grows in clusters
nonmotile
no, facultative anaerobe
yes, facultative halophiles

Question 2

How do you differentiate staphylococcus strains vs. streptococcus? What test is used to differentiate staph aureus? What test is used to differentiate coagulase-negative staph species?

Answer 2

Use a catalase test. If it bubbles, it is catalase positive, indicating staphylococcus.

2. Coagulase test will check specifically for staph aureus
3. Novobiocin test determines epidermidis (sensitive) vs. saprophyticus (resistant)

Question 3

Which staph species has a structure that causes pathogenicity? Describe it.

Answer 3

S. aureus has Protein A on its surface, which inhibits the complement cascade. Other staph species do not have protein a

Question 4

What role does coagulase play in S. aureus and S. lugdunensis?

Answer 4

triggers blood clotting, which surrounds the cell and protects it (will not be detected by the immune system). Fibrinolysis (staphylokinse) dissolves fibrin threds in the blood clots so that S. aureus can be released.

Question 5

Novobiocin is important for distinguishing between____

Answer 5

staph epidermidis (sensitive to novobiocin, doesn’t ferment mannitol) vs. staph sarophyticus (resistant to novobiocin)

Question 6

_______breaks down hyaluronic acid, enabling the bacteria to spread between cells

Answer 6

hyaluronidase

Question 7

______Dissolves fibrin threads in blood clots, allowing S.aureus to free itself from clots

Answer 7

staphylokinase/fibrinolysin

Question 8

MRSA is resistant because___

Answer 8

it produces beta lactamase, which breaks down the beta lactam ring in penicillin

Question 9

Describe color results seen on a blood agar plate

Answer 9

1- hemolytic- partial lysis of rbcs greenish color
2- hemolytic- complete lysis of rbc yellow color, staph aureus
3- hemolytic-RBC lysis (can’t lyse the rbcs)

Question 10

What are two main toxins given off by staphylococcus? What three forms of disease do staph bring about?

Answer 10

-Toxic shock syndrome toxin
Enterotoxins
-noninvasive, cutaneous, systemic

Question 11

what is used to treat staphylococcal infections?

Answer 11

Methicillin- not activated by beta lactamase

Question 12

describe streptococcus

Answer 12

gram positive, cocci, in chains or pairs, facultative anaerobes, have lancefield antigens to determine group

Question 13

If a bacteria is gram positive, tests negative for catalase, and positive for bile esculin it is ____

Answer 13

enterococcus faecalis

Question 14

if a bacteria is gram positive, tests negative for catalase, and is sensitive to bacitracin it is ____

Answer 14

strep pyogenes

Question 15

If a bacteria is gram positive, tests negative for catalase, has beta hemolysis and is resistant to bacitracin it is _____

Answer 15

strep agalactiae

Question 16

The only Group A Strep species is____

Answer 16

strep pyogenes–> strep throat, makes protein M that inhibits opsonization (so cells not phagocytosed), pyrogenic toxins- release cytokines

Question 17

The viridans group of strep can be described as ____ hemolytic and causes these medical problems____, _____, ____

Answer 17

alpha hemolytic

dental problems, meningitis, endocarditis

Question 18

Strep pneumo is _____cellular and causes four diseases

Answer 18

pneumococcal pneumonia, ear infection, bacteremia/endocarditis, pneumococcal meningitis

Question 19

What is a Quellung reaction?

Answer 19

Used to diagnose strep pneumo, is a test in which proteins associate in capsule and antibodies are bound to those proteins; clumping occurs so there is visual swelling of capsule which can be seen in microscope

Question 20

Describe Group B Strep and its diseases

Answer 20

S. agalactiae, gram positve, beta hemolytic, colonizes in GI and GU tracts, causes sepsis in baby, can detect the bacterial colonization in the mother near time of birth to prevent infection of baby