Streptococci

Question 1

Nutritional requirement

Answer 1

Complex, need blood or serum enrich media for isolation

Question 2

group A

S. Pyogeny

Answer 2

G+
Facultative anaerobe
Capsule (HA)
Beta-hemolytic on blood agar 
M protein 
F protein bind fibronectin - helps establish infection

Question 3

Difference between Streptolysin O and S

Answer 3

O is immunogenic

Question 4

What contributes to spread of free dna from local site

Answer 4

DNase

Question 5

Important marker of cutaneous group A streptococcal infections

Answer 5

Anti-DNase B

Question 6

Function of streptokinase

Answer 6

Catalyzes activation of plasmin to lyse blood clots

Question 7

Suppurating Streptococcal Disease

Answer 7

Pharyngitis
Scarlet fever
Skin infection: impetigo, purulent with crusting 
Cellulitis
Erysipelas
Necrotizing Faciitis

Question 8

Nonsuppurative Streptococcal Disease

Acute glomerular nephritis

Answer 8

No GAS present

After pharyngitis or skin infection

Symptoms: facial edema, blood in urine (smoky urine)

Question 9

AGN is due to

Answer 9

Immune complex deposition on the glomerular basement membrane

Question 10

Acute Rheumatic Fever (ARF)

Answer 10

No GAS present

After pharyngitis only

Symptoms: migratory arthritis, subcutaneous nodules, carditis and erythema marginatum

May proceed to rheumatic fever

Question 11

ARF is due to

Answer 11

Cross reactivity of anti-M protein antibody with human cardiac tissue

Question 12

Sources of GAS

Answer 12

Normal flora of skin

Oropharynx

Question 13

GAS causes infection upon ______ of _______

Transmission

Answer 13

Upon penetration of tissue

Person to person

Question 14

What test is used in RF for Ab detection?

GAS

Answer 14

ASO test

Question 15

Ag detection?

GAS

Answer 15

Throat swabs

Question 16

Treatment

GAS

Answer 16

Penicillin

Oxacillin or vancomycin in mixed culture

Question 17

Culture

GAS

Answer 17

Blood agar

Specialized selective agar

Question 18

What is GAS sensitive to?

Answer 18

Bacitracin

Question 19

GBS

which test differentiates a. Galactiae from other streps?

Answer 19

CAMP +

Increased zone of hemolysis

CAMP factor produced by GBS that enhances beta-hemolysis of S. Aureus

Question 20

Clinical problems associated with GBS

Answer 20

Threat to infants infected perinatally (meningitis, bacteremia (sepsis), pneumonia)

Post-partum endometritis, esp after C section

Question 21

GBS

Source

Transmission

Answer 21

Normal flora of GI and Vagina

Vertical transmission: either at birth or via ascension in utero

Question 22

GBS

Virulence factors

Answer 22

Capsule (resist phagocytosis) 
Sialic acid (inhibits alternate pathway of complement)

Question 23

Which is Bacitracin resistant?

Answer 23

GBS

Question 24

Treatment for GBS

Answer 24

Penicillin G
Alone or in combination with Aminoglycosides

Passive immunizations

Question 25

Groups C and G

Answer 25

Non rheumatic | Otherwise like group A

Question 26

Viridans Streptococci

Answer 26

Normal flora of mouth and teeth Alpha hemolytic Resistant to optochin Sub-acute endocarditis Central role in dental carries No Lancefield antigens

Question 27

Treatment of streptococcal endocarditis

Answer 27

Penicillin and antibiotic prophylaxis

Question 28

Streptococcus pneumoniae (SP) Alpha or beta hemolytic?

Answer 28

Alpha - aerobically | Beta - anaerobically

Question 29

SP - bile solubility ?

Answer 29

Positive

Question 30

What disease is SP resistant ?

Answer 30

Chronic granulomatous disease

Question 31

Two distinct characteristics of Streptococcus:

Answer 31

- non motile | - catalase negative

Question 32

Virulence factors for SP

Answer 32

Capsules Biofilm IgA protease (IgA --> Fab and Fc fragments. Prevents opsonization) Adhesins Pneumolysin (destroys the ciliated epithelial cell)

Question 33

SP infections:

Answer 33

Lobar pneumonia (esp sickle cell disease) Meningitis Sinusitis Otitis media

Question 34

Diagnosis of SP:

Answer 34

Quelling rxn - polyvalent anti-capsular Ab are mixed with the bacteria -- inc in refractive mass around the bacteria Bile / optochin sensitive

Question 35

Treatment of SP:

Answer 35

Penicillin G Vancomycin (if P allergy) Vaccines for over 60 and compromised host

Question 36

Enterococcus

Answer 36

Normal flora of large bowel and feces Antibiotic resistance common Nosocomial infection

Question 37

Virulence factors for Enterococci :

Answer 37

Aggregation substance and carbohydrate adhesins: helps in colonization Cytolysin Gelatinase Antibiotic resistance: resistant to aminoglycosides, beta-lactams, vancomycin

Question 38

Cytolysin

Answer 38

Inhibit G+ bacteria and induce local tissue damage

Question 39

Enterococci diagnosis:

Answer 39

Resistant to optochin Doesnt dissolve when exposed to bile

Question 40

Treatment of Enterococci

Answer 40

Ampicillin | Combo of Aminoglycoside and vancomycin for resistant strain

Question 41

Which AA seq does Vancomycin resistant Enterococci have a substitute for?

Answer 41

D-Ala-D-Ala Target for vancomycin