Aerobic gram +ve cocci - strep

Question 1

What is the shape and staining status of streptococci?

Answer 1

Gram positive, spherical

Question 2

Strep do not use oxygen but are not anaerobes. Explain.

Answer 2

Strep do not utilize oxygen since they have no cytochromes, but can tolerate oxygen. Thus, they are not anaerobes

Question 3

Strep tend to organize how?

Answer 3

in chains (they also stain in chains)

Question 4

How are streptococci differentiated from staphylococci?

Answer 4

Strep have colonial morphology and lack catalase enzyme

Question 5

What are the different ways to classify streptococci?

Answer 5

By hemolytic reaction
By Lancefield grouping
By phenotypical characteristics (biochemical tests)

Question 6

What is the classification based on hemolytic reaction?

Answer 6

Can be:
alpha hemolytics - partial hemolysers
Beta hemolytic - completely lyse
Gamma hemolytic - not hemolytic at all

Question 7

What is lancefield grouping?

Answer 7

serotyping of C carbohydrate from cell wall

Question 8

What is the best way to distinguish different strep species?

Answer 8

Through biochemical tests

Question 9

Describe strep pyogenes by its hemophylic group, lancefield group and antibiotic susceptibility.

Answer 9

Beta hemophylic
Lancefield group A
Penicillin susceptible

Question 10

Describe what happens when strep pyogenes infects soft tissues.

Answer 10

Produces necrotizing fasciitis with no gas produced.

Question 11

What are S. pyogenes virulence factors?

Answer 11

Capsule of hyaluronic acid
Fimbria - M protein
Protein F - (fibronectin binding protein)
Exotoxins

Question 12

What to S. pyogenes M proteins do? What are they proportional to?

Answer 12

M proteins on fimbriae help stick to host cells - levels are proportional to virulence

Question 13

What are different diseases causes by S. pyogenes?

Answer 13

Acute suppurative infections
Toxin-mediated syndromes
Post-streptococcal disease

Question 14

What are the different diseases that fall under acute suppurative infections caused by S. pyogenes?

Answer 14

Pharyngitis
Skin and soft tissue infections
Sepsis

Question 15

What is the difference between a primary and secondary sore throat?

Answer 15

Primary sore throat is when that is the focus of the issue and no other symptoms accompany it.
A secondary sore throat is when someone has many other symptoms along with the sore throat

Question 16

What is done with primary sore throats?

Answer 16

Swab the throat and culture to see if it is strep (most likely not)

Question 17

Why do we treat strep throat with antibiotics?

Answer 17

To prevent rheumatic fever.

By and large, treating with antibiotics will not do much to soreness of the throat

Question 18

What is a key characteristic of impetigo?

Answer 18

amber crusts

Question 19

Which type of patients are predisposed to S. pyogenes sepsis?

Answer 19

Splenectomized patients

Question 20

What is the hallmark of erysipelas?

Answer 20

Line of demarcation between involved and uninvolved skin is very apparent.
Texture is like that of an orange (peau d’orange skin)

Question 21

What is very important for any circumscribed lesion with potential to become larger?

Answer 21

Draw a line around it

Question 22

What is a difference between erysipelas and cellulitis?

Answer 22

cellulitis is not as well demarcated

Question 23

What are the toxin-mediated syndromes caused by S. pyogenes?

Answer 23

Scarlett fever

Streptococcal Toxic shock syndrome

Question 24

What are some symptoms of Scarlet Fever?

Answer 24

Pharyngitis with erythematous skin eruption, strawberry tongue and Pastia’s lines

Question 25

What are Pastia's lines due to?

Answer 25

Pyrogenic exotoxin

Question 26

What are Pastia's lines?

Answer 26

Line of hemorrhage along the crease line of the antecubital fossa

Question 27

How is Scarlet fever treated?

Answer 27

with penicillin

Question 28

What is streptococcal toxic shock syndrome due to?

Answer 28

Due to pyrogenic exotoxin acting as a superantigen

Question 29

What are the different post-streptococcal diseases?

Answer 29

Acute glomerulonephritis Rheumatic fever Erythema nodosum

Question 30

Immunologically-mediated diseases triggered by strep infections but the symptoms are not directly caused by the bacterium

Answer 30

Post-streptococcal diseases

Question 31

When does acute GN occur? | Where did the strep need to infect prior?

Answer 31

1-3 weeks post strep infection | Strep could have infected anywhere in the body

Question 32

What strep strains cause acute GN?

Answer 32

small number of nephritogenic strains - defined by M protein and T antigen

Question 33

What are acute GN symptoms?

Answer 33

hematuria, high blood pressure and edema - due to KIDNEY issues

Question 34

Acute GN is a huge reason for what? | Describe the prognosis.

Answer 34

Kidney failure | Good prognosis

Question 35

Will treating the strep infection quickly help with preventing acute GN?

Answer 35

no, prompt treatment of the strep infection is not preventative

Question 36

How long after strep infection does rheumatic fever manifest? Where must the infection originate from?

Answer 36

2-4 weeks | Occurs after S. pyogenes pharyngitis only

Question 37

What are some major differences between acute GN and RF from strep?

Answer 37

acute GN can only be caused by a subset of strep pyogenes, but can be due to an infection from any location - prompt treatment is not preventative RA - can be caused by any strep pyogenes (except M4), but must be from a strep pyogenes pharyngitis, prompt treatment of strep is preventative

Question 38

What is the main factor in developing RF?

Answer 38

Host factors - i.e. whether or not your CT and endocardial antigens cross react with strep pyogenes

Question 39

What are some symptoms/signs of rheumatic fever?

Answer 39

fever, migratory polyarthritis, carditis and other signs

Question 40

What are characteristics of erythema nodosum?

Answer 40

(caused by S. pyogenes) Multiple tender nodules on front of lower legs (below knee) and face NOT only caused as post-strep - can be due to drugs and other infections

Question 41

Most common cause of bacterial pneumonia in communities.

Answer 41

Streptococcus pneumoniae

Question 42

Although classified as cocci, what is the actual shape of Streptococcus pneumoniae?

Answer 42

lancet-shaped (elongated) diplococci

Question 43

What is the hemolytic classification of S. pneumoniae? | Lancefield?

Answer 43

Alpha hemolytic | no lancefield antigen

Question 44

What are the two morphological variants of S. pneumoniae? Which is more virulent?

Answer 44

Rough and smooth | Smooth is encapsulated and thus more virulent

Question 45

S. pneumoniae is part of the normal flora where? | It being carried by people is dependent on what?

Answer 45

Normal throat flora, carried by up to half the population, depending on the season

Question 46

S. pneumoniae is often (~20% of strains) resistant to what?

Answer 46

penicillin

Question 47

What are S. pneumoniae virulence factors?

Answer 47

Autolysin | Pneumolysin

Question 48

Describe autolysin.

Answer 48

Present in S. pneumoniae cell wall and causes colonies to be dime-shaped (tend to digest itself)

Question 49

Describe pneumolysin.

Answer 49

Present in S. pneumoniae cytosol. | Released by autolysin and damages mammalian cell membranes

Question 50

What are diseases caused by S. pneumoniae?

Answer 50

Lower RT infections Upper RT infections Bacterial meningitis Sepsis

Question 51

What are the different LRT infections caused by S. pneumoniae?

Answer 51

community-acquired pneumonia, acute exacerbations of chronic bronchitis

Question 52

What are the different URT infections caused by S. pneumoniae?

Answer 52

pediatric otitis media and sinusitis

Question 53

What type of patients are predisposed to S. pneumoniae sepsis?

Answer 53

Splenectomized patients

Question 54

What disease of RBCs if fatal to people without spleens?

Answer 54

malaria

Question 55

What are the different vaccines for S. pneumoniae?

Answer 55

Pneumovax | Prevnar

Question 56

What type of vaccine is pneumovax? Who is it for?

Answer 56

Polysaccharide vaccine for the elderly and splenectomized

Question 57

What type of vaccine is Prevnar? Who is it used for?

Answer 57

Heptavalant conjugate vaccine | Used for children

Question 58

What is an issue with polysaccharide vaccines?

Answer 58

Very sensitive to lapses in cold-chain - have to be refrigerated, else they spoil rapidly