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Micro and Immunology > Aerobic gram +ve cocci - strep > Flashcards

Aerobic gram +ve cocci - strep Flashcards

1
Q

What is the shape and staining status of streptococci?

A

Gram positive, spherical

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2
Q

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

A

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

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3
Q

Strep tend to organize how?

A

in chains (they also stain in chains)

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4
Q

How are streptococci differentiated from staphylococci?

A

Strep have colonial morphology and lack catalase enzyme

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5
Q

What are the different ways to classify streptococci?

A

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

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6
Q

What is the classification based on hemolytic reaction?

A

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

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7
Q

What is lancefield grouping?

A

serotyping of C carbohydrate from cell wall

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8
Q

What is the best way to distinguish different strep species?

A

Through biochemical tests

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9
Q

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

A

Beta hemophylic
Lancefield group A
Penicillin susceptible

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10
Q

Describe what happens when strep pyogenes infects soft tissues.

A

Produces necrotizing fasciitis with no gas produced.

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11
Q

What are S. pyogenes virulence factors?

A

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

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12
Q

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

A

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

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13
Q

What are different diseases causes by S. pyogenes?

A

Acute suppurative infections
Toxin-mediated syndromes
Post-streptococcal disease

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14
Q

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

A

Pharyngitis
Skin and soft tissue infections
Sepsis

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15
Q

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

A

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

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16
Q

What is done with primary sore throats?

A

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

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17
Q

Why do we treat strep throat with antibiotics?

A

To prevent rheumatic fever.

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

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18
Q

What is a key characteristic of impetigo?

A

amber crusts

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19
Q

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

A

Splenectomized patients

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20
Q

What is the hallmark of erysipelas?

A

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

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21
Q

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

A

Draw a line around it

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22
Q

What is a difference between erysipelas and cellulitis?

A

cellulitis is not as well demarcated

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23
Q

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

A

Scarlett fever

Streptococcal Toxic shock syndrome

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24
Q

What are some symptoms of Scarlet Fever?

A

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

25
Q

What are Pastia’s lines due to?

A

Pyrogenic exotoxin

26
Q

What are Pastia’s lines?

A

Line of hemorrhage along the crease line of the antecubital fossa

27
Q

How is Scarlet fever treated?

A

with penicillin

28
Q

What is streptococcal toxic shock syndrome due to?

A

Due to pyrogenic exotoxin acting as a superantigen

29
Q

What are the different post-streptococcal diseases?

A

Acute glomerulonephritis
Rheumatic fever
Erythema nodosum

30
Q

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

A

Post-streptococcal diseases

31
Q

When does acute GN occur?

Where did the strep need to infect prior?

A

1-3 weeks post strep infection

Strep could have infected anywhere in the body

32
Q

What strep strains cause acute GN?

A

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

33
Q

What are acute GN symptoms?

A

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

34
Q

Acute GN is a huge reason for what?

Describe the prognosis.

A

Kidney failure

Good prognosis

35
Q

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

A

no, prompt treatment of the strep infection is not preventative

36
Q

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

A

2-4 weeks

Occurs after S. pyogenes pharyngitis only

37
Q

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

A

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

38
Q

What is the main factor in developing RF?

A

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

39
Q

What are some symptoms/signs of rheumatic fever?

A

fever, migratory polyarthritis, carditis and other signs

40
Q

What are characteristics of erythema nodosum?

A

(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

41
Q

Most common cause of bacterial pneumonia in communities.

A

Streptococcus pneumoniae

42
Q

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

A

lancet-shaped (elongated) diplococci

43
Q

What is the hemolytic classification of S. pneumoniae?

Lancefield?

A

Alpha hemolytic

no lancefield antigen

44
Q

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

A

Rough and smooth

Smooth is encapsulated and thus more virulent

45
Q

S. pneumoniae is part of the normal flora where?

It being carried by people is dependent on what?

A

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

46
Q

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

A

penicillin

47
Q

What are S. pneumoniae virulence factors?

A

Autolysin

Pneumolysin

48
Q

Describe autolysin.

A

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

49
Q

Describe pneumolysin.

A

Present in S. pneumoniae cytosol.

Released by autolysin and damages mammalian cell membranes

50
Q

What are diseases caused by S. pneumoniae?

A

Lower RT infections
Upper RT infections
Bacterial meningitis
Sepsis

51
Q

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

A

community-acquired pneumonia, acute exacerbations of chronic bronchitis

52
Q

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

A

pediatric otitis media and sinusitis

53
Q

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

A

Splenectomized patients

54
Q

What disease of RBCs if fatal to people without spleens?

A

malaria

55
Q

What are the different vaccines for S. pneumoniae?

A

Pneumovax

Prevnar

56
Q

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

A

Polysaccharide vaccine for the elderly and splenectomized

57
Q

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

A

Heptavalant conjugate vaccine

Used for children

58
Q

What is an issue with polysaccharide vaccines?

A

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

Micro and Immunology (38 decks)

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