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Flashcards in Gram Positive Bacteria Deck (142):
1

What are the antigenic structure on G+ cell walls?

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

2

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

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

3

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

Cocci (round) and Bacilli (rod shaped)

4

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

Catalase + and Catalase -

Catalase + are Staphylococcus
Catalase - are streptococus and enterococcus

5

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

They are catalase + and grow in clusters

6

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

They are catalase - and grow in chains

7

Staphylococcus can be further differentiated based on what feature?

S. aureus is coagulase positive

S. saprophyticus and S. epidermis are coagulase negative

8

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

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

9

Gram + Bacilli can be subdivided based on what characteristic?

Spore-forming and non-spore forming

10

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

Aerobic = Bacillus
Anaerobic= Clostridium

11

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

Filamentous = Nocardia
Non-filamentous = actinomyces

12

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

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

13

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

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

14

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

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

15

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

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

16

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

Clumping factor- a fibrinogen-binding protein

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

17

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

on medical devices

18

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

catalase + and coagulase -

It causes disease on medical devices

19

S. saprophyticus is a cause of ______________________.

urinary tract infections in young women

20

What are the two major reservoirs of S. aureus?

1. Nose
2. Skin

20

What are the two major reservoirs of S. aureus?

1. Nose
2. Skin

21

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

60-90%

21

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

60-90%

22

What kinds of Staph colonize the skin?

S. aureus- intermittent

Coagulase negative staph- everyone

22

What kinds of Staph colonize the skin?

S. aureus- intermittent

Coagulase negative staph- everyone

23

What are the staph syndromes of the skin?

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

23

What are the staph syndromes of the skin?

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

24

What toxicities are associated with S. aureus?

1. Scalded skin syndrome/bollus impetigo
2. Toxic Shock Syndrome

24

What toxicities are associated with S. aureus?

1. Scalded skin syndrome/bollus impetigo
2. Toxic Shock Syndrome

25

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

Exfoliative Toxin A and B

S. Aureus

25

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

Exfoliative Toxin A and B

S. Aureus

26

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

TSS is associated with TSST-1.

There is an inapparent site of infection for TSS

26

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

TSS is associated with TSST-1.

There is an inapparent site of infection for TSS

27

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

Just about anywhere. It can cause:
bacteremia, osteomyelitis, endocarditis, septic arthritis

27

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

Just about anywhere. It can cause:
bacteremia, osteomyelitis, endocarditis, septic arthritis

28

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

epidermis
dermis
subcutaneous fascia
deep fascia
muscle

28

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

epidermis
dermis
subcutaneous fascia
deep fascia
muscle

29

What layer of skin is affected by impetigo and erysipelas?

epidermis and outer dermis

29

What layer of skin is affected by impetigo and erysipelas?

epidermis and outer dermis

30

What layers of skin are affected by cellulitis?

Dermis and subcutaneous fascia

30

What layers of skin are affected by cellulitis?

Dermis and subcutaneous fascia

31

What layers of skin are affected by necrotizing fasciitis?

deep fascia (below subcut. fat)

31

What layers of skin are affected by necrotizing fasciitis?

deep fascia (below subcut. fat)

32

What layer of the skin is affected by myelitis?

muscle

32

What layer of the skin is affected by myelitis?

muscle

33

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

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

33

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

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

34

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

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

34

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

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

35

What are the secreted virulence factors of S. aureus?

1. protease, lipase, hyaluronidase
2. Panton-Valentine leukocidin- kills phagocytic cells

35

What are the secreted virulence factors of S. aureus?

1. protease, lipase, hyaluronidase
2. Panton-Valentine leukocidin- kills phagocytic cells

36

What bacteria secrete Paton-Valentine leukocidin?
How do they provide virulence?

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

36

What bacteria secrete Paton-Valentine leukocidin?
How do they provide virulence?

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

37

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

1. Capsule
2. secreting Paton-Valentine leukocidin

37

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

1. Capsule
2. secreting Paton-Valentine leukocidin

38

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

60-70 worldwide
50% at parkland

38

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

60-70 worldwide
50% at parkland

39

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

They are gram + cocci that organize in chains
They are catalase negative which differentiates them from staph

39

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

They are gram + cocci that organize in chains
They are catalase negative which differentiates them from staph

40

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

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

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

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

What are examples of B- hemolytic strep?

1. S. pyogenes (Group A)- bacitracin sensitive
2. S. agalacitae (Group B)- bacitracin resistant

41

What are examples of B- hemolytic strep?

1. S. pyogenes (Group A)- bacitracin sensitive
2. S. agalacitae (Group B)- bacitracin resistant

42

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

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

42

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

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

43

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

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

43

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

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

44

What bacteria are alpha hemolytic?

1. S. pneumonia- encaspulated, optochin sensitive
2. Viridians Streptococci- no capsule, optichin resistanth

44

What bacteria are alpha hemolytic?

1. S. pneumonia- encaspulated, optochin sensitive
2. Viridians Streptococci- no capsule, optichin resistanth

45

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

Optochin test

S. pneumonia is sensitive and viridians is resistant

45

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

Optochin test

S. pneumonia is sensitive and viridians is resistant

46

What is different structurally between the alpha hemolytic streps?

S. pneumonia is encapsulated and viridians has no capsule

46

What is different structurally between the alpha hemolytic streps?

S. pneumonia is encapsulated and viridians has no capsule

47

What are examples of gamma hemolytic strep?

1. Enterococcus
2. Peptostreptococcus

47

What are examples of gamma hemolytic strep?

1. Enterococcus
2. Peptostreptococcus

48

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

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

48

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

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

49

What disease is caused by S. pyogenes?

Pharyngitis

49

What disease is caused by S. pyogenes?

Pharyngitis

50

What beta hemolytic strep is associated with colon cancer?

Lancefield group D - S. bovis

50

What beta hemolytic strep is associated with colon cancer?

Lancefield group D - S. bovis

51

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

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

51

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

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

52

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?

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

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?

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

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

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

53

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

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

54

What allows adherence of group A strep (pyogenes)

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

54

What allows s. pyogenes to evade immune detection?

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

54

What allows s. pyogenes to invade and spread?

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

54

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

skin and throat causing:

Local infection, invasive infection, toxicity syndromes, poststreptococcal syndromes

54

What type of strep causes tonsillopharyngitis (strep throat)?

Group A beta-hemolytic strep (pyogenes)

Sonetimes C and G but less frequently

54

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

1. Rheumatic fever
2. Acute Post- Streptococcal Glomerulonephritis

54

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

S. pyogenes
It follows pharyngitis or skin infection

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

54

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

Capsule- antiphagocytic

54

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

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

54

How many capsular serotypes are there for s. pneumoniae?

Over 90.
There are 23 in the adult vaccine and 12 in the pediatric protein conjugated vaccine

54

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

It serves an anti-phagocytic purpose.
It is downregulated in the throat but is expressed in invasive disease

54

Describe the gram stain and hemolysis pattern of enterococcus.

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

54

Where do enterococcus tend to live?

In the intestines of animals

54

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

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

54

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

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

54

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

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

54

What is unique about the capsule of B. anthracis?

It is polyglutamic acid instead of polysaccharides

54

What are the two potential habitats of B. anthracis?

1. soil
2. GI tracts of animals

54

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

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

What are the three main clinical syndromes associated with anthrax?

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

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

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

What three factors make up the anthrax toxin?

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

54

Describe the gram stain of Listeria monocytogenes.
Is L. monocytogenes spore forming? Is it filamentous?

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

54

What is the hemolytic capability of Listeria monocytogenes?

Beta hemolytic

54

What gives s. pyogenes its toxicity?

Pyrogenic exotoxins (speB)
Superantigens

54

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

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

54

What toxicity syndromes are associated with Group A strep?

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

54

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

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

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

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

54

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

Type 3 because sailic acid is poorly immunogenic

54

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

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

54

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

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

54

What six clinical presentations are associated with s. pneumonia?

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

54

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

S.pneumonia

54

What three virulence factors are associated with s. pneumonia?

1. polysaccharide adhesion factors
2. polysaccharide capsule
3. pneumolysin

54

What is the secreted virulence factor of S. pneumoniae?

Pneumotoxin- it lyses host cells

54

What is unique about the growth of enterococcus?

It prefers to grow in 6.5% salt

54

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

Enterococcus has the same antigens as group D (S. bovis)
Enterococcus grows in 6.5% salt and S. bovis does not

54

What two things allow lab identification of enterococcus?

1. It grows at 6.5% salt (differential from S. bovis)
2. It is tolerant of bile

54

What are the two species of enterococcus

E. faecium (15%)
E. faecalis (85%)

54

What is a vegetative cell?

A cell that grows normally by binary fission

54

What are the two spore forming G+ cells?

Bacillus and Clostridium

54

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

macrophages

54

What are "anthrax zones"?

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

54

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

In the bacteremia stage

54

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

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

54

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

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

54

Where are B. cereus found?

1.soil
2. GI tract of herbivores

54

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

1. GI disease- emetic and diarrhea
2. Blood stream infection and cellulitis (usually only in immunocompromised)

54

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

GI- the toxin is heat stable and usually in fried rice
Diarrheal- the toxin is heat labile and in meat/ sauce

54

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

It is associated with tumbling motility

54

What is the oxygen dependence of listeria monocytogenes?

aerobic

54

What is unique about the growth pattern of listeria monocytogenes?

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

What is the treatment for listeria monocytogenes?

ampicillin ** first choice

second line = trimethoprim sulfamethoxazole

68

What does the EF toxin of B. anthracis do?

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