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LECOM Microbiology MS1 > Gram Positive Cocci Part 2 (Exam 1) > Flashcards

Gram Positive Cocci Part 2 (Exam 1) Flashcards

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1
Q

How will strep appear on gram stain

A

gram positive cocci in chains or pairs

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2
Q

What will the catalase result of strep be

A

negative

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3
Q

What are the environmental requirements for strep

A

facultative anaerobes, some capnophilic

complex nutritional requirements
carbohydrates are fermented and produce lactic acid

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4
Q

How are strep classified

A

serology (lancefield groupings)
hemolytic patterns
biochemical properties

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5
Q

What are Lancefield groups

A

Group specific cell wall antigens in strep; polysaccharide or teichoic acid

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6
Q

What are the group names of Lancefield groups

A

Groups A-W

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7
Q

What Lancefield groups are most important

A

ABCDFG

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8
Q

How are cell wall antigens of strep detected

A

immunologic assays

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9
Q

What are the medically important strep

A

A
B
D
S pneumonia, viridans strep –have no lancefield group

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10
Q

What is Group A strep

A

Strep pyogenes

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11
Q

What is Group B strep

A

Strep agalactiae

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12
Q

What is Group B strep

A

E. faecalis (enterococcus)

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13
Q

What are the different types of hemolysis displayed by strep on blood agar

A

alpha beta and gamma

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14
Q

What strep are beta hemolytic

A

strep pyogenes

strep agalactiae

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15
Q

What strep are alpha hemolytic

A

strep pneumoniae

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16
Q

What strep are gamma hemolytic

A

Enterococcus spp

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17
Q

What group does strep pyogenes fall into

A

group A beta hemolytic strep

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18
Q

WHat diseases are associated with strep pyogenes

A

strep throat

skin infections: necrotizing fasciitis (flesh eating bacteria)

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19
Q

How will strep pyogenes appear on gram stain

A

gram positive
cocci
in short chains

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20
Q

What type of capsule is seen on S. pyogenes

A

hyaluronic acid

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21
Q

What does the capsule on S. pyogenes prevent

A

phagocytosis

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22
Q

What adhesins are seen in in S. pyogenes

A

Lipoteichoic acid
M like proteins
F protien

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23
Q

What enzymes contribute to the virulence of strep pyogenes

A

streptolysin S and O
streptokinase
DNAse
C5a peptidase

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24
Q

What is the most important virulence factor of strep pyogenes

A

M protein

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25
Q

What is the streptococcal pyrogenic exotoxin

A

superantigen, binds outside normal peptide binding groove and causes a cytokine storm

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26
Q

What titer is used for rheumatic fever

A

ASO titer

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27
Q

What is ASO titer

A

anti-streptolysin O (lyse red blood cells)

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28
Q

What are the effects of M protein of strep pyogenes

A

binds to matrix proteins
antiphagocytic
Degrades complement C3b

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29
Q

What two diseases of S pyogenes are caused by antigenic variation

A

Rheumatoid fever

Acute glomerulonephritis

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30
Q

What strains produce rheumatoid fever

A

Rheumatigenic strains

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31
Q

What strains produce acute glomerulonephritis

A

M12

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32
Q

What type of reaction is rheumatic fever

A

Type II hypersensitivity

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33
Q

What is the mechanism of S. pyogenes in rheumatic fever

A

hypersensitivity reaction
molecular mimicry
antibodies attack heart tissue

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34
Q

What does rheumatic fever look like in children

A

congestive heart failure

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35
Q

What type of reaction is acute glomerulonephritis

A

Type III hypersensitivity

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36
Q

WHat is the mechanism that causes acute glomerulonephritis

A

immune complexes are formed with anatibodies for strep pyogenes that plug up the kidneys

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37
Q

What toxin is responsible for the rash in scarlet fever

A

pyrogenic exotoxins from S. pyogenes

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38
Q

What are the pyrogenic exotoxins

A

4 immunologically distinct heat-labile toxins ABCF

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39
Q

Where are the pyrogenic exotoxins found

A

coded on lysogenized phage

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40
Q

What are the presentations of scarlet fever

A

after strep throat
rash on chest and upper arms (sandpaper rash)
strawberry tongue

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41
Q

What toxin of S. pyogenes displays antigenic conversion

A

pyrogenic exotoxin is a superantigen on a lysogenic phage

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42
Q

What is the function of streptolysin S and O

A

hemolysins

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43
Q

What do hemolysins do

A

lyse WBC, platelets, RBCs and stimulate release of lysosomal enzymes

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44
Q

Is streptolysin S immunogenic

A

no

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45
Q

Is streptolysin O immunogenic

A

yes

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46
Q

What causes the beta hemolysis of S pyogenes on blood agar

A

streptolysin S

47
Q

WHat type of S pyogenes infection will lack anti-ASO antibodies

A

skin infections: streptolysin O inhibitied by cholesterol in skin lipids

48
Q

What is the function of streptokinases in S. pyogenes

A

cleave plasminogen to plasmin

contributes to spread of bacteria

49
Q

what does plasmin do

A

cleave fibrin and fibrinogen, dissolves clots

50
Q

What is the function of DNase (A-D) in strep pyogenes infections

A

depolymerize free DNA in pus

51
Q

What does depolymerizing free DNA in pus cause

A

reduced viscosity of abscess, helps it spread

52
Q

What is DNase a marker for

A

marker of cutaneous infection

53
Q

What is the funciton of C5a peptidase in S. pyogenes

A

degrades complement component C5a, inhibits chemotaxis of phagocytes

54
Q

Where is strep pyogenes normally found

A

oroparynx of healthy children and young adults

55
Q

What percentage of the population are carriers for strep pyogenes

A

15-20%

56
Q

How is strep pyogenes transmitted for pharyngitis

A

respiratory droplets

57
Q

How is strep pyogenes transmitted for soft-tissue infections

A

skin contact, organisms introduced into tissues through break in the skin

58
Q

What are the diseases that are unique to strep pyogenes

A

rheumatic fever
scarlet fever
acute post-streptococcal glomerulonephritis

59
Q

How will strep throat present

A

sore throat, fever, malaise, headache, posterior pharynx erythema with exudate

60
Q

What causes the exudate in strep throat

A

pus in the back of the throat from neutrophils

61
Q

What causes the pain and inflammation in strep throat

A

neutrophils

62
Q

What are the clinical symptoms of scarlet fever

A

erythematous rash on upper chest, spreads to extremities

Strawberry tongue

63
Q

How will S. pyogenes present as a skin infection

A

pyoderma

Impetigo

64
Q

What is pyoderma

A

any purulent skin infection

65
Q

What is impetigo symptoms

A

vesicles progess to pustules, rupture, and crust over into honey-crusted lesions

66
Q

Where are viridans streptococci found

A

normal flora of GI, GU, and URT

67
Q

What are the hemolysis patterns of viridans strep

A

alpha hemolytic

68
Q

WHat are the clinical diseases associated with Strep mutans

A

Dental plaque cavities

Subacute bacterial endocarditis

69
Q

What are the clinical diseases associated with Strep sanguinis

A

bacteremia and endocarditis

70
Q

What are the clinical diseases associated with strep gallolyticus

A

bacteremia and endocarditis in people with colon cancer

71
Q

How will strep pneumoniae appear on gram stain

A

gram positive cocci in pairs

72
Q

How will strep pneumoniae appear on culture

A

alpha hemolytic, round mucoid colonies on culture

73
Q

What is the most common cause of community acquired pneumonia

A

strep pneumoniae

74
Q

How is strep pneumoniae transmitted

A

respiratory droplets

75
Q

Where is strep pneumo normally found

A

normal flora of URT

76
Q

When does strep pneumo disease occur

A

organisms spread, often preceded by respiratory viral infection and damage ot ciliated epithelial cells

77
Q

What is the only gram positive diplococci discussed

A

streptococcus pneumoniae

78
Q

What is the most important virulence factor of strep pneumoniae

A

capsule

79
Q

What is the function of the capsule in strep pneumoniae

A

phagocytosis and aids in crossing the BBB

80
Q

What organisms with have an IgA protease

A

strep pneumoniae
Neisseria meningitidis
haemophilus influenza

81
Q

What is the funciton of IgA protease in S. pneumoniae

A

cleave IgA antibodies

82
Q

What is the function of pneumolysin in S. pneumoniae

A

binds cholesterol and creates pores that kill ciliated epithelial cells

binds Fc portion of antibody and activates classic complement pathway

83
Q

What type of vaccine is used for S. pneumoniae

A

conjugate vaccine

84
Q

What is the conjugate vaccine aimed towards

A

the capsule attached to protein to cause isotype switching to IgA

85
Q

How will pneumococcal pneumonia present

A

chills, fever, productive cough with blood-tinged sputum

many PMNs
lobar pneumonia

86
Q

Besides pneumonia, what other clinical diseases are associated with strep pneumonia

A 
meningitis
sinusitis
otitis media
bacteremia
endocarditis
87
Q

Who is at risk with miningitis from strep pneumonia

A

children and elderly

88
Q

WHo is at risk with sinusitis and otitis media from strep pneumonia

A

young children

89
Q

How can microscopy of S. pneumoniae be used for diagnosis

A

lancet shaped gram positive diplococci

quellung reaction

90
Q

How will strep pneuoniae appear on blood agar

A

alpha hemolytic

91
Q

What tests can be used to identify strep pneumoiae from viridans strep

A

bile solubility test

optochin test

92
Q

S pneumoniae colonies do what in bile solubility test

A

dissolve

93
Q

S. pneumoniae grown in the presence of optochin is what

A

sensitive

94
Q

What are the enteric cocci discussed

A

E. faecalis

E. faecium

95
Q

What cell wall antigen do enterococci display

A

group D cell wall antigen

96
Q

How will enterococci appear on gram stains and in culture

A

gram positive cocci in short chains

white colonies on culture

97
Q

What are the environmental requirements of enterococci

A

Facultative anaerobes

grow in high salt levels

98
Q

How are enterococci differentiated from strep

A

enterococci are bile resistant and will grow

strep are bile sensitive

99
Q

Describe the pathogenesis of enterococci

A

commensal organisms with no toxin

limited potential for causing disease

100
Q

describe the epidemiology of enterococci

A

recovered in feces and acquired from contaminated food or water

101
Q

Where is E. faecalis found

A

large intestine and GU tract

102
Q

What are the secrete factors that play a role in virulence of enterococci

A

cytolysin
chemoattractant for PMNs
Gelatinase

103
Q

What do cytolysins do

A

inhibit gram + bacteria, induces local tissue damage

104
Q

What does gelatinase do

A

hydrolyze gelatin, collagen, hemoglobin

105
Q

What type of antibiotic resistance is exhibited by enterococci

A

multiple plasmid and chromosome genes

resistant to aminoglycosides, beta lactams, vancomycin

106
Q

What are the clinical diseases associated with enterococci

A

UTIs
Peritonitis
Endocarditis

107
Q

What are symptoms with a UTI

A

dysuria and pyuria

108
Q

What are symptoms of peritonitis

A

abdominal swelling and tenderness after abdominal trauma or surgery

109
Q

What patients are at risk for acquiring enterococci infections

A

pts with urinary, IV catheters

Pts on broad spectrum antibiotics

110
Q

What is the catalase reaction results of enterococci

A

negative

111
Q

How are enterococci cultured

A

grow well on blood agar, chocolate agar, and bile esculin agar

112
Q

On bile esculin agar, how do enterococci appear

A

black pigment

113
Q

What are the biocheical tests that can be used to diagnoses enterococci

A

resistance to optochin
bile resistant
PYR+

LECOM Microbiology MS1 (22 decks)

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