streptococcus, pneumococci, listeria, anthrax

Question 1

What is the meaning of beta, alpha and gamma hemolysis?

Answer 1

Beta hemolysis: complete hemolysis
alpha hemolysis: partial hemolysis
gamma hemolysis: no hemolysis

Question 2

What is another name for group A strep? (GAS)

Answer 2

streptococcus pyogenes

Question 3

How would you distinguish between group A and group b strep?

Answer 3

Group A strep is sensitive to bacitracin while group B strep is not.

Question 4

What does the CAMP test identify? How does it work?

Answer 4

Identifies group B strep. Camp factor damages the RBC, which when combined with the enzyme secreted by S. aureus, creates a zone of hemolysis.

Question 5

What is another test to differentiate GBS?

Answer 5

Hippurate hydrolysis.

Question 6

What kind of hemolysis would you see with group A/B strep?

Answer 6

Group A and B strep both show alpha hemolysis. However, the field of clearance is larger with group A strep

Question 7

If strep tests positive for hydrolysis of esculin in bile salts, what species would you suspect?

Answer 7

Group D strep: Enterococcus faecalis will hydrolyze and turn the tube brown.

Question 8

Name all the species within Groups A, B, and D streptococci

Answer 8

Group A strep: streptococcus pyogenes
Group B strep: streptococcus agalactiae
Group D strep: 1. Enterococcus: E faecalis
2. Non-enterococcus: streptococcus bovis

Question 9

What are the main differences between enterococcus and non-enterococcus strep?

Answer 9

Enterococcus: Growth in high salt medium
Resistant to antibiotics
Causes UTI, bacteremia, and endocarditis
Non-enterococcus: Lack of growth in high salt medium
Sensitive to penicillin
Causes endocarditis

Question 10

What are the nontypeable streptococci species?

Answer 10

Strep pneumoniae

Strep viridans

Question 11

What is unique about the morphology of S. pneumoniae?

Answer 11

lancet-shaped diplococci

Question 12

What are two methods of distinguishing S. pneumoniae from S. viridans?

Answer 12

1. Strep pneumoniae is sensitive to optochin

2. Strep pneumoniae is lysed by bile

Question 13

Where is each species of strep localized to, normally?

Answer 13

group A strep: oral flora (less common) 
group B strep: vaginal flora (less common)
group D strep: colonic flora
S. pneumoniae: oral flora (less common)
S. viridans: oral flora

Question 14

What is the morphology of most strep species?

Answer 14

Gram + cocci in chains (exception is strep pneumoniae)

Question 15

Are most streptococci catalase positive or negative?

Answer 15

Catalase negative

Question 16

What kind of hemolysis will you observe with group A strep?

Answer 16

beta hemolysis

Question 17

What is the significance of the M protein for S pygenes?

Answer 17

Antiphagocytic molecule. Specific types cause rheumatic fever/glomerulonephritis

Question 18

Does Group A strep have a capsule? a pilus?

Answer 18

Yes, has a capsule composed of hyluronic acid

Also has a pilus for adhesion to pharyngeal cells

Question 19

What are the three types of diseases caused by GAS?

Answer 19

1. Pyogenic diseases
2. Toxigenic diseases
3. immunologic diseases

Question 20

Give an example of pyogenic diseases caused by GAS

Answer 20

pharyngitis
impetigo and cellulitis
necrotizing fasciitis
pneumonia,meningitis

Question 21

Give examples of toxigenic diseases caused by GAS

Answer 21

scarlet fever

toxic shock syndrome

Question 22

Which proteins in GAS help with adhesion to host cells?

Answer 22

M protein
Protein F
lipoteichoic acid

Question 23

Which proteins help with evasion of host defenses?

Answer 23

capsule, M protein

Question 24

Which toxins released by GAS are related to pyogenic inflammation?

Answer 24

hyaluronidase
streptokinase
streptodornase
streptolysin O
streptolysin S
exotoxin B

Question 25

Which toxins released by GAS are related to toxigenic disease?

Answer 25

``` erythrogenic toxin (scarlet fever) pyrogenic exotoxin (TSS) These are both superantigens ```

Question 26

Does isolation of group A strep in a nontoxic individual indicate infection?

Answer 26

No

Question 27

What does scarlet fever look like?

Answer 27

sandpaper like rash all over | Pastia's lines (red lines at the axillary and inguinal regions)

Question 28

How soon after a GAS pharyngeal infection would you see rheumatic fever?

Answer 28

2 weeks

Question 29

What is the cause of Rheumatic fever?

Answer 29

streptococcal M proteins react with antigens in the joint, heart, and brain tissues

Question 30

How can you prevent rheumatic fever?

Answer 30

By treating GAS within 8 days of onset.

Question 31

How soon after a GAS skin infection would you expect to see acute glomerulonephritis?

Answer 31

2-3 weeks

Question 32

What is the point of the ASO titer?

Answer 32

Confirmat previous/recent streptococcal infection

Question 33

What are the symptoms of acute glomerulonephritis?

Answer 33

hypertension, edema, smoky urine

Question 34

What are the four ways in which you could diagnose GAS?

Answer 34

1. culture skin/pharynx, grow, check for beta hemolysis and inhibition by bacitracin 2. rapid strep test 3. culture invasive tissue 4. elevated ASO titer

Question 35

How do you treat group A strep?

Answer 35

penicillin G or erythromycin

Question 36

What are the symptoms of GBS?

Answer 36

1. neonatal sepsis/meningitis | 2. postpartum endometritis/wound infection in adults

Question 37

How do you treat GBS?

Answer 37

penicillin or ampicillin

Question 38

What kind of hemolysis do you see with group D strep?

Answer 38

alpha or gamma hemolysis

Question 39

Where are Group D streptococci found? What unique property do they have that allows them to grow there?

Answer 39

Colonic bacterial flora | Has the ability to grow in bile

Question 40

How do you treat group D strep?

Answer 40

If enterococci: use vancomycin + aminoglycoside | If S. bovis, use penicillin

Question 41

You observe strep species that is lysed by bile and inhibited by optochin. What do you suspect? What kind of hemolysis would you expect?

Answer 41

Strep pneumoniae. Alpha hemolytic colonies.

Question 42

What kind of hemolysis does strep pneumoniae have?

Answer 42

alpha hemolysis

Question 43

What is the quellung reaction?

Answer 43

Rxn where antibody binds to bacterial capsule and allows the capsule to be visualized. Basis for typing reaction. If there is no quellung rxn, means bacteria has no capsule

Question 44

What are the pathogenic factors of S. pneumoniae?

Answer 44

lipoteichoic acid pneumolysin (alpha hemolysis) IgA protease (cleaves mucosal igA for better colonization)

Question 45

How do you treat S. pneumoniae?

Answer 45

Otitis media: amoxicillin pneumonia: fluoroquinolone and amox Meningitis: vancomycin + ceftriaxone

Question 46

What are the two pneumococcal vaccines? Which is more effective for whom?

Answer 46

Pneumococcal polyvalent: (T cell independent) better for elderly Pneumococcal conjugate: (T cell dependent): better for children under 2

Question 47

What kind of hemolysis does strep viridans produce?

Answer 47

alpha hemolysis

Question 48

What is the response of strep viridans to bile/optochin?

Answer 48

Not lysed by bile. Resistant to optochin

Question 49

What are the important species within strep viridans?

Answer 49

S. sanguis S. mutans S. mitis

Question 50

We know that strep viridans is an important part of the oral flora. What is it clinically relevant?

Answer 50

It can enter the blood stream after dental surgery to cause endocarditis Can also cause oral abscess that can lead to sinus/brain abscess after dental surgery

Question 51

How do you treat strep viridans?

Answer 51

Penicillin for abscess. Penicillin/vancomycin for endocarditis.

Question 52

What is the morphology of Bacillis anthracis?

Answer 52

Large gram positive rods, spore-forming, aerobic

Question 53

What would happen if the anthrax colonies were plated on blood agar?

Answer 53

no hemolysis

Question 54

What is unique about the anthrax capsule?

Answer 54

Made up of poly-glutamic acid

Question 55

What is a risk factor for developing anthrax?

Answer 55

Exposure to grazing animals or their products: hides

Question 56

What is unique about anthrax spores?

Answer 56

They are centrally located

Question 57

What are the important factors in the pathogenesis of anthrax?

Answer 57

1. Protective antigen: Forms pores in macrophages 2. Edema factor: Causes edema in association with PA adenylate cyclase 3. Lethal factor: Lethal in association with PA phosphokinase of MAPK pathway

Question 58

What are the clinical syndromes of anthrax?

Answer 58

1. cutaneous anthrax 2. inhalation anthrax 3. gastrointestinal anthrax

Question 59

How would you treat and prevent anthrax?

Answer 59

1. Cipro/doxycycline | 2. There is also a vaccine, which is not commonly used

Question 60

What are the properties of listeria monocytogenes?

Answer 60

Small aerobic gram + rod. Non spore forming

Question 61

Where is listeria monocytogenes commonly found?

Answer 61

animals, plants, unpasteurized milk and cheese. Commonly found in refridgerated foods because it grows well at low temperature.

Question 62

Is listeria motile?

Answer 62

Yes. tumbles!

Question 63

What happens if you plate listeria on a blood agar plate?

Answer 63

narrow zone of beta hemolysis

Question 64

Describe the pathogenesis of listeria

Answer 64

Invades mononuclear phagocytic cells (macrophage) - Grows intracellularly - Evades endosomes through listeriolysin O

Question 65

What are the clinical symptoms of listeria?

Answer 65

Neonatal sepsis and meningitis | or in immunocompromised host

Question 66

How do you treat listeria?

Answer 66

Ampicillin | trimethoprim-sulfamethoxazole

Question 67

What is the most important virulence factor of group A strep?

Answer 67

M protein. It determines whether the pt will later have rheumatic fever vs glomerulonephritis because it is an important antigen.

Question 68

What does steptolysin O do?

Answer 68

hemolysin it is oxygen-labile and an important antigen

Question 69

What is streptolysin S?

Answer 69

Oxygen stable hemolysin. NOT antigenic

Question 70

pyrogenic exotoxin A

Answer 70

Toxin responsible for streptococcal toxic shock syndrome. Similar to staphylococcal TSST. Also a superantigen

Question 71

Exotoxin B

Answer 71

Responsible for Strep A's "flesh eating behavior"

Question 72

What is the most common cause of bacterial pharyngitis?

Answer 72

Streptococcus pyogenes

Question 73

What bacteria can form impetigo--honey colored crusted lesions of the skin?

Answer 73

Either Staph aureus or GAS

Question 74

What is the most common cause of endocarditis?

Answer 74

Viridans strep. Common after dental surgery

Question 75

A patient has endocarditis. What are the possible organisms that could be responsible?

Answer 75

1. Strep viridans (think oral surgery) 2. Staphylococcus aureus 3. Staphylococcus epidermidis 4. Enterococcus 5. Group A strep Evidence of endocarditis=splinter hemorrhage and enlarged spleen