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Bugs and Drugs > Gram Positive Bacteria > Flashcards

Gram Positive Bacteria Flashcards

1
Q

What are the antigenic structure on G+ cell walls?

A

teichoic acid and lipoteichoic acid that stick out of the peptidoglycan cell wall

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2
Q

What color do G+ stain on a gram stain? Why?

A

They stain purple because the crystal violet does not get washed away with alcohol.
The more crosslinking of the peptidoglycan affects the stain

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3
Q

Gram positive bacteria can be broken into two large categories. What are they?

A

Cocci (round) and Bacilli (rod shaped)

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4
Q

Cocci bacteria can be subdivided into two groups. What are they?
What two families of bacteria does this separate?

A

Catalase + and Catalase -

Catalase + are Staphylococcus
Catalase - are streptococus and enterococcus

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5
Q

Are staphylococci catalase + or -? How do they grow?

A

They are catalase + and grow in clusters

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6
Q

Are streptococcus catalase + or -? How do they grow?

A

They are catalase - and grow in chains

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7
Q

Staphylococcus can be further differentiated based on what feature?

A

S. aureus is coagulase positive

S. saprophyticus and S. epidermis are coagulase negative

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8
Q

What does catalase do? What disease would exacerbate due to the catalase production?

A

Catalase breaks down hydrogen peroxide which allows staphylococcus to utilize oxygen and avoid phagocytic killing.

Catalase + organisms are dangerous in chronic granulomatous disease because they form phagolysosomes but can’t degrade product. Catalase would remove the remaining H2O2

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9
Q

Gram + Bacilli can be subdivided based on what characteristic?

A

Spore-forming and non-spore forming

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10
Q

G+ rods that are spore forming can be divided into what two categories? What is an example of a bacteria in each category?

A 
Aerobic = Bacillus
Anaerobic= Clostridium
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11
Q

G+ rods that are NOT spore forming can be divided based on what characteristic? What is an example of a bacteria in each category?

A 
Filamentous = Nocardia
Non-filamentous = actinomyces
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12
Q

What is the diagnostic test that would show you that a G+ cocci was Staphylococcus?

A

Catalase test (can it break down H2O2?– drop peroxide on the bacterial colony. If it bubbles, it is catalase positive)

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13
Q

Describe the oxygen consumption, gram staining, shape and arrangement of staphylococcus?

A

They are aerobic, G+ cocci that are organized in clusters

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14
Q

S. aureus produces __________ which differentiates it from S. saprophyticus and S. epidermis.

A

Coagulase which contributes to virulence by acting as a factor for spreading in tissue.

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15
Q

Because of the coagulase, what must you do to an abscess that involves staphylococcus?

A

You must lance the abscess and drain it so the antibiotics can get to it

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16
Q

In addition to coagulase, what other diagnostic factor is unique to staph?

A

Clumping factor- a fibrinogen-binding protein

When you add S. aureus to human plasma, it will clump the plasma

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17
Q

What is the major site of disease for S. epidermis?

A

on medical devices

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18
Q

S. epidermis is catalase _______ and coagulase ______. It causes disease on _______.

A

catalase + and coagulase -

It causes disease on medical devices

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19
Q

S. saprophyticus is a cause of ______________________.

A

urinary tract infections in young women

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20
Q

What are the two major reservoirs of S. aureus?

A
  1. Nose

2. Skin

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20
Q

What are the two major reservoirs of S. aureus?

A
  1. Nose

2. Skin

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21
Q

What percent of people will have s. aureus colonize in their noses?

A

60-90%

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21
Q

What percent of people will have s. aureus colonize in their noses?

A

60-90%

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22
Q

What kinds of Staph colonize the skin?

A

S. aureus- intermittent

Coagulase negative staph- everyone

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22
Q

What kinds of Staph colonize the skin?

A

S. aureus- intermittent

Coagulase negative staph- everyone

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23
Q

What are the staph syndromes of the skin?

A
  1. folliculitis
  2. Furuncles and carbuncles
  3. Impetigo, cellulitis, gas gangrene, necrotizing fasciitis, wound infection
  4. Mastitis
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23
Q

What are the staph syndromes of the skin?

A
  1. folliculitis
  2. Furuncles and carbuncles
  3. Impetigo, cellulitis, gas gangrene, necrotizing fasciitis, wound infection
  4. Mastitis
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24
Q

What toxicities are associated with S. aureus?

A
  1. Scalded skin syndrome/bollus impetigo

2. Toxic Shock Syndrome

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24
Q

What toxicities are associated with S. aureus?

A
  1. Scalded skin syndrome/bollus impetigo

2. Toxic Shock Syndrome

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25
Q

What toxins are associated with scalded skin/bollus impetigo? What bacteria are they associated with?

A

Exfoliative Toxin A and B

S. Aureus

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25
Q

What toxins are associated with scalded skin/bollus impetigo? What bacteria are they associated with?

A

Exfoliative Toxin A and B

S. Aureus

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26
Q

What toxin is associated with S. aureus toxic shock syndrome? Where is the toxicity apparent?

A

TSS is associated with TSST-1.

There is an inapparent site of infection for TSS

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26
Q

What toxin is associated with S. aureus toxic shock syndrome? Where is the toxicity apparent?

A

TSS is associated with TSST-1.

There is an inapparent site of infection for TSS

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27
Q

When s. aureus infections become systematic, where will it end up?

A

Just about anywhere. It can cause:

bacteremia, osteomyelitis, endocarditis, septic arthritis

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27
Q

When s. aureus infections become systematic, where will it end up?

A

Just about anywhere. It can cause:

bacteremia, osteomyelitis, endocarditis, septic arthritis

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28
Q

What are the layers of the skin from out to in?

A 
epidermis
dermis
subcutaneous fascia
deep fascia
muscle
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28
Q

What are the layers of the skin from out to in?

A 
epidermis
dermis
subcutaneous fascia
deep fascia
muscle
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29
Q

What layer of skin is affected by impetigo and erysipelas?

A

epidermis and outer dermis

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29
Q

What layer of skin is affected by impetigo and erysipelas?

A

epidermis and outer dermis

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30
Q

What layers of skin are affected by cellulitis?

A

Dermis and subcutaneous fascia

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30
Q

What layers of skin are affected by cellulitis?

A

Dermis and subcutaneous fascia

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31
Q

What layers of skin are affected by necrotizing fasciitis?

A

deep fascia (below subcut. fat)

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31
Q

What layers of skin are affected by necrotizing fasciitis?

A

deep fascia (below subcut. fat)

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32
Q

What layer of the skin is affected by myelitis?

A

muscle

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32
Q

What layer of the skin is affected by myelitis?

A

muscle

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33
Q

What are the five major virulence factors of s. aureus?

A
  1. capsule - antiphagocytic
  2. Protein A- binds Ig to evade immune system
  3. Clumping factor- permits attachment to ECM
  4. Coagulase- matrix attachment
  5. Secreted factors
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33
Q

What are the five major virulence factors of s. aureus?

A
  1. capsule - antiphagocytic
  2. Protein A- binds Ig to evade immune system
  3. Clumping factor- permits attachment to ECM
  4. Coagulase- matrix attachment
  5. Secreted factors
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34
Q

What is protein A? What bacteria is it associated with?

A

Protein A a virulence factor associated with S. aureus that allows it to bind Ig and evade immune response

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34
Q

What is protein A? What bacteria is it associated with?

A

Protein A a virulence factor associated with S. aureus that allows it to bind Ig and evade immune response

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35
Q

What are the secreted virulence factors of S. aureus?

A
  1. protease, lipase, hyaluronidase

2. Panton-Valentine leukocidin- kills phagocytic cells

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35
Q

What are the secreted virulence factors of S. aureus?

A
  1. protease, lipase, hyaluronidase

2. Panton-Valentine leukocidin- kills phagocytic cells

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36
Q

What bacteria secrete Paton-Valentine leukocidin?

How do they provide virulence?

A

S. aureus secretes Paton-Valentine leukocidin which kills phagocytic cells

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36
Q

What bacteria secrete Paton-Valentine leukocidin?

How do they provide virulence?

A

S. aureus secretes Paton-Valentine leukocidin which kills phagocytic cells

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37
Q

What are the two ways S. aureus avoids being phagocytosed?

A
  1. Capsule

2. secreting Paton-Valentine leukocidin

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37
Q

What are the two ways S. aureus avoids being phagocytosed?

A
  1. Capsule

2. secreting Paton-Valentine leukocidin

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38
Q

What percent of patients have MRSA? What percent at Parkland?

A

60-70 worldwide

50% at parkland

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38
Q

What percent of patients have MRSA? What percent at Parkland?

A

60-70 worldwide

50% at parkland

39
Q

How do Streptococci gram stain? What is the shape? What tests allow you to know that it is strep?

A

They are gram + cocci that organize in chains

They are catalase negative which differentiates them from staph

39
Q

How do Streptococci gram stain? What is the shape? What tests allow you to know that it is strep?

A

They are gram + cocci that organize in chains

They are catalase negative which differentiates them from staph

40
Q

Strep can be divided based on hemolysis. What are the three categories of hemolysis and how would each look on a blood agar?

A
  1. B- hemolysis would have complete clearing around the bacteria
  2. Alpha hemolysis would appear greenish (partial hemolysis)
  3. Gamma- hemolysis would have no clearing (no hemolytic capabilities)
40
Q

Strep can be divided based on hemolysis. What are the three categories of hemolysis and how would each look on a blood agar?

A
  1. B- hemolysis would have complete clearing around the bacteria
  2. Alpha hemolysis would appear greenish (partial hemolysis)
  3. Gamma- hemolysis would have no clearing (no hemolytic capabilities)
41
Q

What are examples of B- hemolytic strep?

A
  1. S. pyogenes (Group A)- bacitracin sensitive

2. S. agalacitae (Group B)- bacitracin resistant

41
Q

What are examples of B- hemolytic strep?

A
  1. S. pyogenes (Group A)- bacitracin sensitive

2. S. agalacitae (Group B)- bacitracin resistant

42
Q

What bacteria is group A B-hemolytic? What drug is it sensitive to that differentiates it from other B-hemolytic bacteria?

A

S. pyogenes- is GABHS and it is sensitive to bacitracin

42
Q

What bacteria is group A B-hemolytic? What drug is it sensitive to that differentiates it from other B-hemolytic bacteria?

A

S. pyogenes- is GABHS and it is sensitive to bacitracin

43
Q

What bacteria is group B B-hemolytic? What drug is it resistant to which differentiates it from group A?

A

S. agalactiae is group B beta hemolytic strep. It is resistant to bacitracin which differentates it from S. pyogenes

43
Q

What bacteria is group B B-hemolytic? What drug is it resistant to which differentiates it from group A?

A

S. agalactiae is group B beta hemolytic strep. It is resistant to bacitracin which differentates it from S. pyogenes

44
Q

What bacteria are alpha hemolytic?

A
  1. S. pneumonia- encaspulated, optochin sensitive

2. Viridians Streptococci- no capsule, optichin resistanth

44
Q

What bacteria are alpha hemolytic?

A
  1. S. pneumonia- encaspulated, optochin sensitive

2. Viridians Streptococci- no capsule, optichin resistanth

45
Q

What test can determine whether an alpha hemolytic strep is S. pneumonia and viridians strep?

A

Optochin test

S. pneumonia is sensitive and viridians is resistant

45
Q

What test can determine whether an alpha hemolytic strep is S. pneumonia and viridians strep?

A

Optochin test

S. pneumonia is sensitive and viridians is resistant

46
Q

What is different structurally between the alpha hemolytic streps?

A

S. pneumonia is encapsulated and viridians has no capsule

46
Q

What is different structurally between the alpha hemolytic streps?

A

S. pneumonia is encapsulated and viridians has no capsule

47
Q

What are examples of gamma hemolytic strep?

A
  1. Enterococcus

2. Peptostreptococcus

47
Q

What are examples of gamma hemolytic strep?

A
  1. Enterococcus

2. Peptostreptococcus

48
Q

B- hemolytic strep are further classified into Lancefield groups. What are the groups and give the major bacteria in each group.

A 
A- S. pyogenes
B- S. agalactiae
C- S. equisimilis
D- S. bovis
G- S. dysgalactiae
48
Q

B- hemolytic strep are further classified into Lancefield groups. What are the groups and give the major bacteria in each group.

A 
A- S. pyogenes
B- S. agalactiae
C- S. equisimilis
D- S. bovis
G- S. dysgalactiae
49
Q

What disease is caused by S. pyogenes?

A

Pharyngitis

49
Q

What disease is caused by S. pyogenes?

A

Pharyngitis

50
Q

What beta hemolytic strep is associated with colon cancer?

A

Lancefield group D - S. bovis

50
Q

What beta hemolytic strep is associated with colon cancer?

A

Lancefield group D - S. bovis

51
Q

You would use the Bacitracin Test to determine if a bacteria is what?

A

GABHS- S. agalactiae is resistant to bacitracin so there is no zone of inhibition around the bacitracin soaked disk

51
Q

You would use the Bacitracin Test to determine if a bacteria is what?

A

GABHS- S. agalactiae is resistant to bacitracin so there is no zone of inhibition around the bacitracin soaked disk

52
Q

You have a blood agar plate smeared with two bacterial strains. Both appear to be beta-hemolytic and leave clear areas on the blood agar. You place a bacitracin soaked disk on the plate. Which bacteria would you suspect if there was still complete clearing?
What would you expect if there was no blood hemolyzed around the disk?

A

If there was complete hemolysis, you would assume S. agalactiae because it is resistant to bacitracin

If there was non-hemolyzed blood around the bacitracin disk, that means the bacteria was sensitive to the bacitracin and was not able to hemolyze the blood. This is S. pyogenes

52
Q

You have a blood agar plate smeared with two bacterial strains. Both appear to be beta-hemolytic and leave clear areas on the blood agar. You place a bacitracin soaked disk on the plate. Which bacteria would you suspect if there was still complete clearing?
What would you expect if there was no blood hemolyzed around the disk?

A

If there was complete hemolysis, you would assume S. agalactiae because it is resistant to bacitracin

If there was non-hemolyzed blood around the bacitracin disk, that means the bacteria was sensitive to the bacitracin and was not able to hemolyze the blood. This is S. pyogenes

53
Q

What four virulence factors are associated with Group A beta-hemolytic strep?

A
  1. adherence
  2. immune evasion
  3. invasion and spread
  4. toxicity
53
Q

What four virulence factors are associated with Group A beta-hemolytic strep?

A
  1. adherence
  2. immune evasion
  3. invasion and spread
  4. toxicity
54
Q

What allows adherence of group A strep (pyogenes)

A
  1. M proteins
  2. lipoteichoic acid
  3. fibronectin binding proteins
  4. hyaluronic acid capsule
54
Q

What allows s. pyogenes to evade immune detection?

A
  1. M proteins
  2. capsule
  3. Ig binding proteins
  4. C5a peptidase
54
Q

What allows s. pyogenes to invade and spread?

A
  1. SD(protease)
  2. Streptolysin S and O
  3. DNAase
  4. streptokinase
  5. hylauronidase
54
Q

What are the two main areas where s. pyogenes is found?

A

skin and throat causing:

Local infection, invasive infection, toxicity syndromes, poststreptococcal syndromes

54
Q

What type of strep causes tonsillopharyngitis (strep throat)?

A

Group A beta-hemolytic strep (pyogenes)

Sonetimes C and G but less frequently

54
Q

What are the post-infectious sequelae of S. pyogenes infections?

A
  1. Rheumatic fever

2. Acute Post- Streptococcal Glomerulonephritis

54
Q

What bacteria is associated with Acute Post- Streptococcal Glomerulonephritis?
What phase of infection does it follow?
What is the presentation?

A

S. pyogenes
It follows pharyngitis or skin infection

Proteinuria leads to renal failure and Ig complexes form in the glomeruli

54
Q

What virulence factors are associated with group B beta-hemolytic strep (s. agalactiae)?

A

Capsule- antiphagocytic

54
Q

What does the polysaccharide adhesion factor of S. pneumoniae allow it to do?

A

adhere to N-acetylglucosamine and to 3-Gal for attachment to epithelial cells

54
Q

How many capsular serotypes are there for s. pneumoniae?

A

Over 90.

There are 23 in the adult vaccine and 12 in the pediatric protein conjugated vaccine

54
Q

What is the purpose of S. pneumonia having a capsule?
Where is the capsule down regulated?
When is the capsule expressed?

A

It serves an anti-phagocytic purpose.

It is downregulated in the throat but is expressed in invasive disease

54
Q

Describe the gram stain and hemolysis pattern of enterococcus.

A

It is a gram + diplococci (like pneumococcus) but it is gamma hemolytic or weakly alpha hemolytic

54
Q

Where do enterococcus tend to live?

A

In the intestines of animals

54
Q

Enterococci are poor pathogens so why are they of any concern to physicians?

A
  1. They cause nosocomial infections - UTI, wound infection, bacteremia, endocarditis
  2. They are vancomycin resistant VRE
54
Q

What is sporulation?
What is a spore?
What is germination?

A

Sporulation- developmental process where a spore forms within a vegetative cell
Spore- heat-resistant, metabolically dormant form
Germination- spore becomes a vegetative cell

54
Q

What is the gram stain profile, oxygen dependence, motility and hemolytic ability of B. anthracis?

A

It is a G+ rod
Non-motile
Aerobic
non-hemolytic

54
Q

What is unique about the capsule of B. anthracis?

A

It is polyglutamic acid instead of polysaccharides

54
Q

What are the two potential habitats of B. anthracis?

A
  1. soil

2. GI tracts of animals

54
Q

Who would be most likely to be infected by B. anthracis?

A

People who work with hides (because spores can be in animal furs)
People who work in abattoirs (slaughterhouses) because spores can be in guts

54
Q

What are the three main clinical syndromes associated with anthrax?

A
  1. cutaneus- most common. spores get in skin breaks (10-15 mortality)
  2. GI- ingestion of contaminated meat (20-30 mortality)
  3. Inhalation- accidental (hides) or bioterror
54
Q

Describe the process that occurs after the inhalation of b. anthracis spores.

A
  1. spores are inhaled
  2. macrophages ingest spores
  3. macrophages go to lymph nodes
  4. Spores germinate in the macrophage in lymph node
  5. Vegetative b. anthracis makes toxins to kill macrophage and other tissue
  6. bacteremia leads to: hemorrhagic mediastinitis, hemorrhagic menigitis
54
Q

What three factors make up the anthrax toxin?

A

PA- protective antigen
EF- Edema Factor
LF- lethal factor

54
Q

Describe the gram stain of Listeria monocytogenes.

Is L. monocytogenes spore forming? Is it filamentous?

A

It is a G+ rod (coccobacillary) that does NOT form spores and is non-filamentous

54
Q

What is the hemolytic capability of Listeria monocytogenes?

A

Beta hemolytic

54
Q

What gives s. pyogenes its toxicity?

A 
Pyrogenic exotoxins (speB)
Superantigens
54
Q

What do antibiotics do to the duration of strep throat? What are their major benefit?

A

They do NOT shorten the duration of illness but they prevent rheumatic fever

54
Q

What toxicity syndromes are associated with Group A strep?

A
  1. Scarlet fever- skin infection follows throat, spe genes, lysogenic phases
  2. Strep TSS- follows invasive disease, bacteremia, superantigen
54
Q

What bacteria is associated with rheumatic fever?
What phase of infection does it follow?
What are the medically relevant presentations?

A

S. pyogenes
It follows pharyngitis only
It is associated with heart abnormalities, fever, joint swelling, chorieform movements

Ig cross reaction between M-type and cardiac tissue

54
Q

What infections are associated with group B beta hemolytic strep (s. agalactiae)?

A
  1. Post-partum infections- peurperal sepsis
  2. Neonatal infections- bacteremia/meningitis
  3. Other
54
Q

What type capsule of Group B strep is most associated with disease? Why?

A

Type 3 because sailic acid is poorly immunogenic

54
Q

Describe the gram staining, hemolysis pattern and drug sensitivities of S. pneumoniae.

A

It is G+ diplococci that grows in lancets
It is alpha hemolytic
It is optochin sensitive

54
Q

Most alpha hemolytic strep are are resistant to __________. The only exception is _______.

A

Alpha strep are resistant to optochin except for s. pneumonia which is sensitive

54
Q

What six clinical presentations are associated with s. pneumonia?

A
  1. otitis media
  2. sinusitis
  3. conjunctivitis
  4. chronic bronchitis
  5. pneumonia
  6. meningitis
54
Q

What bacteria is responsible for the most cases of community acquired pneumonia?

A

S.pneumonia

54
Q

What three virulence factors are associated with s. pneumonia?

A
  1. polysaccharide adhesion factors
  2. polysaccharide capsule
  3. pneumolysin
54
Q

What is the secreted virulence factor of S. pneumoniae?

A

Pneumotoxin- it lyses host cells

54
Q

What is unique about the growth of enterococcus?

A

It prefers to grow in 6.5% salt

54
Q

What lancefield group streptococcus has the same antigenic profile as enterococcus? How can you differentiate the two bacteria?

A

Enterococcus has the same antigens as group D (S. bovis)

Enterococcus grows in 6.5% salt and S. bovis does not

54
Q

What two things allow lab identification of enterococcus?

A
  1. It grows at 6.5% salt (differential from S. bovis)

2. It is tolerant of bile

54
Q

What are the two species of enterococcus

A

E. faecium (15%)

E. faecalis (85%)

54
Q

What is a vegetative cell?

A

A cell that grows normally by binary fission

54
Q

What are the two spore forming G+ cells?

A

Bacillus and Clostridium

54
Q

B. anthracis are intracellular pathogens that prefer to live in ______________/.

A

macrophages

54
Q

What are “anthrax zones”?

A

places where there are alot of B. anthracis spores in the soil

54
Q

When does the capsule of b. anthracis play a role in pathogenesis?

A

In the bacteremia stage

54
Q

What does the LF (lethal factor) of B. anthracis do?

A
  1. MAPK (mitogen activated protein kinase) that interferes with intracellular signaling
54
Q

What is the gram staining and oxygen dependence of B. cereus?

A

It is a G+ rod that is aerobic and spore-forming

54
Q

Where are B. cereus found?

A
  1. soil

2. GI tract of herbivores

54
Q

What are the clinical presentations of a B. cereus infection?

A
  1. GI disease- emetic and diarrhea

2. Blood stream infection and cellulitis (usually only in immunocompromised)

54
Q

What is different between the toxin that causes GI disease in b. cereus and the toxin that causes diarrheal disease?

A

GI- the toxin is heat stable and usually in fried rice

Diarrheal- the toxin is heat labile and in meat/ sauce

54
Q

Is listeria monocytogenes motile? If so, what kind of motion is it associated with?

A

It is associated with tumbling motility

54
Q

What is the oxygen dependence of listeria monocytogenes?

A

aerobic

54
Q

What is unique about the growth pattern of listeria monocytogenes?

A

It is aerobic, facultative intracellular pathogen that grows in the cytoplasm of cells.
What is unique is that it grows best at “deli-temperature”

54
Q

What is the treatment for listeria monocytogenes?

A

ampicillin ** first choice

second line = trimethoprim sulfamethoxazole

68
Q

What does the EF toxin of B. anthracis do?

A
  1. It is a calmodulin-dependent adenyl cyclase that interferes with the macrophages production of cytokines
  2. causes leakage of fluid from vessels to interstitium

Bugs and Drugs (21 decks)

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