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Microbiology and Parasitology > Bacteria Associated With Skin Infections 1 > Flashcards

Bacteria Associated With Skin Infections 1 Flashcards

1
Q

Some bacteria associated with skin infections

A 
Staphylococcus
Streptococcus
Erysipelothrix
Bacillus
Clostridium
Mycobacterium
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2
Q

Some general Characteristics of Staphylococcus

A 
Gram positive cocci in grape-like cluster
Facultative anaerobe
Some are capsulated
Non-motile
Non-spore forming
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3
Q

Classification of Staphylococcus

A

S. aureus
S. epidermidis
S. saprophyticus

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4
Q

Biotypes of S. aureus

A

Biotypes A, B, C, D

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5
Q

Most commonly found biotype in humans

A

Biotype A

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6
Q

S. aureus is involved the pathogenesis of

A

Superficial (Localized) Infection
Deep (Systemic) Infection
`Toxigenic diseases

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7
Q

Nosocomial Staphylococcus bacteria found in medical instruments or devices (including catheters, CSF shunts, prosthetic heart valve implants)

A

S. epidermidis

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8
Q

S. epidermidis is involved the pathogenesis of

A

Endocarditis associated with valvular prosthesis
Intravenous catheter infection
Peritonitis in patients undergoing CAPD
Ventricular shunt infections

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9
Q

S. saprophyticus is involved the pathogenesis of

A

Urinary tract infection in young sexually active women

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10
Q

Antigenic structures of Staphylococcus

A

Capsule
Slime layer
Protein A
Peptidoglycan-teichoic acid complex

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11
Q

True or False.

Antigenic structures are not always associated with the virulence factors.

A

True

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12
Q

Virulence Factor of Staphylococcus

A 
Capsule
Slime layer
Protein A
Polysaccharide A (Ribitol Teiochoic Acid)
Extracellular enzymes
Toxins
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13
Q

This is a virulence factor that is produced by some S. aureus strains (≥ 8 capsular types identified) and anti- phagocytic

A

Capsule

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14
Q

This is a virulence factor that is only produced by S. epidermidis

A

Slime layer

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15
Q

This is a virulence factor that is involved in adherence and persistence on foreign body; main factor contributing to biofilm formation

A

Slime layer

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16
Q

This is a virulence factor that is a surface protein convalently bound to peptidoglycan

A

Protein A

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17
Q

This is a virulence factor that is regularly present in human strains of S. aureus but not found in (coagulase-negative Staphylocccus or CONS)

A

Protein A

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18
Q

This is a virulence factor that is binds non-specifically with Fc portion of IgG

A

Protein A

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19
Q

When protein A binds to the Fc portion of IgG, it

A

Prevents Fc-mediated opsonization
Induces complement activation by generating chemotactic factors
Used in antigen detection (co-agglutination test)

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20
Q

This is the part of Polysaccharide A that provides rigid exoskeleton and has interpeptide bridge connecting oligoglycine peptides

A

Peptidoglycan

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21
Q

This is the part of Polysaccharide A that is composed of water soluble polymers of ribitol or glycerol phosphate

A

Teichoic acid

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22
Q

An extracellular enzyme that hydrolyzes hyaluronic acid in connective tissues

A

Hyaluronidase

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23
Q

Also known as spreading factor

A

Hyaluronidase

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24
Q

An extracellular enzyme that enhances invasion and survival in tissues by binding cells together and rendering the intercellular spaces passable to pathogen

A

Hyaluronidase

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25
Q

Also known as fat-splitting enzyme

A

Lipase

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26
Q

An extracellular enzyme that splits fats and oils

A

Lipase

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27
Q

An extracellular enzyme that is essential for survival of Staphyloccoccus in sebaceous areas of the body and in the formation of furuncles and carbuncles

A

Lipase

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28
Q

Also known as fibrinolysin

A

Staphylokinase

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29
Q

An extracellular enzyme that dissolves fibrin clots

A

Staphylokinase

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30
Q

An extracellular enzyme that lays down fibrin barrier during abscess formation to prevent the spread of organism that is bound in the center of the abscess

A

Free coagulase

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31
Q

True or False.
Hyaluronidase, lipase and staphylokinase are used for the spreas of the organism in the body while coagulase is for the localization of the organism.

A

True

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32
Q

Type of toxin that is expressed by about 2-4% of S. aureus and is a pore-forming cytotoxin causing leukocyte destruction and tissue necrosis

A

Leukocidin (e.g. Panton Valentine)

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33
Q

Type of toxin that is phage-encoded

A

Leukocidin

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34
Q

Two protein components of Leukocidin

A

LukS-PV (Slow)

LukF-PV (Fast)

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35
Q

Difference of LukS-PV from LukF-PV

A

Electrophoretic mobility

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36
Q

Type of toxin associated with recurrent skin and soft tissue infections and necrotizing pneumonia

A

Leukocidin

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37
Q

Four major types of hemolytic toxins

A

Alpha
Beta
Gamma
Delta

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38
Q

Toxin responsible for causing damage to red cell membrane and produce hemolytic zones on BAP

A

Hemolytic toxins

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39
Q

Major hemolytic toxin

A

Alpha

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40
Q

Hemolytic toxin that forms transmembrane pores and has lethal, dermonecrotic, and leucocidal activities

A

Alpha

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41
Q

Hemolytic toxin formed by majority of human strains of S. aureus but not CONS

A

Alpha

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42
Q

Hemolytic toxin that lipid binding domain that inserts directly into the lipid bilayer of the cell membrane → pores → cell death

A

Alpha

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43
Q

Toxin that produces intraepidermal splitting of tissues, blister formation and sssociated with S. aureus phage group II

A

Exfoliative (epidermolytic) toxins

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44
Q

Exfoliative toxin that recognize, hydrolyze desmosomes in the skin and cleave Desmoglein 1

A

Serine proteases

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45
Q

Four types of exfoliative toxins

A

Type A, B C, D

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46
Q

Major types of exfoliative toxins

A

ETA and ETB

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47
Q

Toxin that is a family of secreted proteins acting as superantigens which stimulate and enhance the lymphocyte response

A

Pyrogenic exotoxins

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48
Q

Two major types of pyrogenic toxins

A

Enterotoxins

Toxic Shock Syndrome Toxin-1

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49
Q

Seven antigen types of enterotoxins

A

A, B, C1, C2, D, E, F

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50
Q

Antigenic types of enterotoxins that cause food poisoning

A

A and D

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51
Q

Antigenic type of enterotoxins that cause necrotizing enterocolitis

A

B

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52
Q

Pyrogenic exotoxin that is synonymous with Enterotoxin F and associated with menstrual infections in women

A

Toxic Shock Syndrome Toxin-1 (TSST-1)

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53
Q

Superficial (localized) infections caused by S. aureus

A

Impetigo
Folliculitis
Furuncles
Carbuncles

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54
Q

Deep (systemic) diseases caused by S. aureus

A

Acute osteomyelitis
Acute endocarditis
Pneumonia

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55
Q

Toxigenic diseases caused by S. aureus

A

Staphylococcal Scalded Skin Syndrome (SSSS/ Ritter’s Disease)
Staphylococcal food poisoning
Toxic Shock Syndrome

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56
Q

True or False.

90% of impetigo cases are caused by S. aureus while the remaining 10% are caused by Group A Streptococci (GAS).

A

True

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57
Q

Type types of impetigo

A 
Bullous impetigo (exclusively by S. aureus)
Non-bullous impetigo (by Staph, Strep or both)
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58
Q

More common in children
Occur in warm, humid environments
Highly contagious
Spread by direct contact with lesions or with nasal carriers

A

Impetigo

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59
Q

Toxin mediated (exfoliative toxin) and accounts for 30% of impetigo cases

A

Bullous impetigo

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60
Q

Type of impetigo that is characterized by vesicles and bullae, when ruptured leaves ligth brown/yellow crusts with oozingn exudates

A

Bullous impetigo

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61
Q

True or False.

Bullous impetigo has fewer lesions than non-bullous impetigo.

A

True

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62
Q

Type of impetigo that represents host response to infection, no toxin is needed to produce clinical manifestations

A

Non-bullous impetigo

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63
Q

True or False.

Non-bullous impetigo is more contagious than the bullous impetigo.

A

True

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64
Q

Type of impetigo that accounts for >70% of impetigo cases

A

Non-bullous impetigo

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65
Q

Formation of the stiking characteristic of non-bullous impetigo

A

Macule/ papule → vesicles/ pustules → rupture leaving honey- colored crusts which discharge pus when pressured

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66
Q

Superficial infection that can occur through shaving, scratching or with any injury to the skin

A

Folliculitis

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67
Q

Follicular-based pustule, most commonly superficial or deep

A

Folliculitis

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68
Q

Most characteristic pustular lesion produced by Staph

A

Furuncles (boils)

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69
Q

Development of furuncles

A

Start as hard, tender, red nodule surrounding a hair follicle → abscess → pus discharged from center → resolve

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70
Q

True or False.

Furuncles does not need surgery and no antibiotic treatment.

A

True

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71
Q

True or False.

No manipulations should be done because it will disrupt the fibrin barrier that will be the start of dissemination.

A

True

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72
Q

Superficial inflammation that arise in hair-bearing areas where there is friction, occlusion, perspiration and may be isolated or multiple

A

Furuncles

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73
Q

Development of carbuncles

A

Start as smooth, dome-shaped, acutely tender, painful lesion → develop into swollen, painful area discharging pus from several sites

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74
Q

Clustered boils but is deeper, more sever, develop and heal more slowly

A

Carbuncles

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75
Q

Frequent areas where carbuncles are found

A

Nape of the neck, back or thighs

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76
Q

Reason why carbuncles are more severe than furuncles

A

It can be disseminated to vital organs like cavernous sinus or the subarachnoid space

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77
Q

Toxigenic disease that is characterized by stripping of superficial layers of the skin from the underlying tissue (involves exfoliative toxin)

A

SSSS/Ritter’s Disease

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78
Q

Most frequently involved age group

A

Infants and children <5 yrs

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79
Q

Major cause

A

S. aureus phage group II (most commonly, type 71)

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80
Q

Laboratory diagnosis of Staphylococcus

A 
Gram stain
Culture
Differential test
Susceptibility test
Serology
Serotyping
Phage typing
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81
Q

Gram stain findings of Staphylococcus

A

Gram positive cocci in clusters
0.5 – 1.5 micrometer in diameter
Gram variable within neutrophils, in resolving lesions, in the presence of antibiotics, and in old cultures

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82
Q

Type of culture needed by Staphylococcus

A

Unenriched media

7.5%-10% NaCl and in 40% bile

83
Q

True or False.
High concentration of NaCl is a selective medium for Staphylococcus allow growth of S. aureus but inhibit growth for other species.

A

True

84
Q

Media used for diagnosing Staphylococcus

A

Blood Agar Plate
Mannitol Salt Agar
Phenyl Ethyl Alcohol Agar

85
Q

Type of media that form smooth, raised colonies and mucoid, if encapsulated

A

BAP

86
Q

Selective and differential media for S. aureus

A

MSA

87
Q

True or False.

S. aureus is mannitol fermenting.

A

True

88
Q

True or False.

Pathogenic staphylococci ferment mannitol and produce acid.

A

True

89
Q

MSA contains

A

1% mannitol
7.5% NaCl
Phenol Red as pH as indicator

90
Q

Results of MSA

A

Yellow: (+) acid producing mannitol fermenter

Pink or red: (-) non-mannitol fermenters

91
Q

Staphylococcus species that are mannitol fermenters

A

S. aureus

S. saprophyticus

92
Q

Two types of differential test used for Staphulococcus

A

Catalase test

Coagulase test

93
Q

Test that differentiates staphylococci from streptococci

A

Catalase test

94
Q

Reagent used in Catalase test

A

3% H2O2

95
Q

Positive catalase test is seen as

A

Bubble formation/effervescence of gas (Immediate)

96
Q

Results of catalase test

A

Streptococcus (-)

Staphylococcus (+)

97
Q

Test that distinguishes the different species of Staphylococcus

A

Coagulase

98
Q

Two types of coagulases secreted by S. aureus

A

Staphylocoagulase

von Willebrand factor binding protein

99
Q

Coagulase that activates human prothrombin

A

Staphylocoagulase

100
Q

Coagulase that activates human, rabbit, mouse prothrombin

A

von Willebrand factor binding protein

101
Q

Coagulase test that detects bound coagulase/clumping factor produced exclusively by S. aureus

A

Slide test

102
Q

Results of slide coagulase test

A

If the Slide test is positive no need to do the tube test; confirmed S. aureus
If negative proceed to tube test

103
Q

Coagulase test that detects free coagulase and causes clotting of citrated plasma in the presence of coagulase reacting factor (CRF)

A

Tube test

104
Q

Coagulase test that is for suspected S. aureus that fail to produce bound coagulase

A

Tube test

105
Q

True or False.

Coagulase test is specific in detecting Staphylococcus aureus.

A

True

106
Q

Test that is used for complete workup culture and sensitivity test after identification

A

Susceptibility test

107
Q

Test that aids in choice of systemic drugs and an epidemiologic tool

A

Susceptibility test

108
Q

Type of test that shows that antibody detection has no value

A

Serology

109
Q

Test that is adjunct or supplementary to phage typing

A

Serotyping

110
Q

Test for epidemiologic tracing of infection and depends on differing susceptibilities to lysis by phages, particularly Phage II

A

Phage typing

111
Q

Suppurative infections are prevented and controlled by

A

Cleanliness, hygiene, and meticulous hand washing
Aseptic management of lesions
Isolation of persons with open lesions
Suppression/cure of nasal carriage

112
Q

General chracteristics of streptococcus

A 
Gram positive cocci in chains
Evident in broth medium
Facultative anaerobe
Some are encapsulated
Some are flagellated
Non- spore forming
Capsuled
113
Q

Characterized by a small zone of beta surrounded by alpha hemolysis

A

Alpha prime hemolysis

114
Q

This is based on group specific carbohydrate antigen (C-CHO) because amino sugar determines serologic specificity

A

Lancefield pattern

115
Q

Components
GAS: _____________
GBS: _____________
GDS: _____________

A

GAS: rhamnose-N-acetylglucosamine
GBS: rhamnose-glucosamine
GDS: glycerol teichoic acid

116
Q

Streptococcus groups

A

A-H, K-V (20 groups)

117
Q

Groups of Human Streptococcus pathogen

A

A-G

118
Q

Human Streptococcus pathogen that is of greater significance

A

A and B

119
Q

Nucleotide-based typing scheme

A

emm classification system

120
Q

Molecular gold standard for GAS typing for M protein- producing strains

A

emm classification system

121
Q

Sequencing of the emm gene that encodes the M protein based on its amino acid sequence variability of the N terminus (5’ end) such as Streptococcus pyogenes

A

emm classification system

122
Q

These are used for species which cannot be grouped under the existing ones and to speciate Viridans Streptococci

A

Biochemical reactions

123
Q

Antigenic structures of GAS

A 
Capsule
Pili
Protein antigens (M, F, G,T proteins)
C5a peptidase
Group-specific polysaccharide (C-CHO)
124
Q

Virulence factors for GAS

A 
Capsule
Lipoteichoic acid
M protein
F protein
G protein
C5a peptidase
Serum Opacity Factor
Pyrogenic (Erythogenic) Exotoxins
Hemolysins
Spreading Factors
125
Q

Virulence factor composed of hyaluronic acid

A

Capsule

126
Q

Virulence factor that is not immunogenic because of its antigenic disguise, and anti-phagocytic

A

Capsule

127
Q

Major virulence factor of Streptococcus pneumoniae

A

Capsule

128
Q

Virulence factor that is a component of pili and binds with M protein, mediating oral/ pharyngeal and epithelial attachment and subsequent colonization

A

Lipoteichoic acid

129
Q

Major virulence factor for GAS

A

M protein

130
Q

Virulence factor that is a component of a pili anti- phagocytic and dominantly binds to epidermis

A

M protein

131
Q

M protein is anti-phagocytic because

A

It prevents alternative complement pathway opsonization

132
Q

True or False.
M proteins are strongly immunogenic because specific antibodies are produced against it. Hence, it is difficult to come up with vaccines for M-protein.

A

True

133
Q

Virulence factor that is a fibronectin-binding protein

A

F protein

134
Q

F protein + M protein

A

Mediates nasopharyngeal adherence

135
Q

Surface-bound endopeptidase and cleaves C5a

A

C5a peptidase

136
Q

Anti-polymorphonuclear leukocyte chemo-attractant

A

C5a peptidase

137
Q

Virulence factor that is an alpha-lipoproteinase and produces opalescence in horse serum broth

A

Serum Opacity Factor

138
Q

Adjunct to M typing

A

Serum Opacity Factor

139
Q

True or False.

Pyrogenic or Erythrogenic Exotoxins are protein in nature.

A

True

140
Q

Four antigenic types of pyrogenic exotoxins

A

A, B, C, D

141
Q

Most significant antigenic type of pyrogenic exotoxins

A

Exotoxin A

Exotoxin B

142
Q

ETA or ETB.

Associated with rash in scarlet fever and TSSL

A

ETA

143
Q

ETA or ETB.

Responsible for tissue destruction in necrotizing fasciitis

A

ETB

144
Q

ETA or ETB.

Superantigen - stimulates and enhances a response

A

ETA

145
Q

Streptococcal gangrene

A

ETB

146
Q

ETA or ETB.

Produced only by lysogenized strains (including bacteriophage)

A

ETA

147
Q

Basis of Dick’s tests

A

Erythrogenic toxin

Presence of erythema or redness of the test site

148
Q

Basis of Schultz-Charlton test

A

Anti-erythrogenic toxin
Presence of anti-blanching phenomenon
Rash fade

149
Q

Virulence factor responsible for beta-hemolysis on BAP of Streptococcus pyogenes

A

Hemolysins (Cytotoxic)

150
Q

2 distinct types of Streptolysin

A

Streptolysin O

Streptolysin S

151
Q 
SO or SS.
Oxygen labile (will not produce if not on surface)
A

SO

152
Q

SO or SS.

Hemolytic in reduced form (to see if there is hemolysis, stab should be performed)

A

SO

153
Q

SO or SS.

Oxygen stable

A

SS

154
Q

SO or SS.

Responsible for subsurface hemolysis

A

SO

155
Q

SO or SS.

Serum soluble

A

SS

156
Q

SO or SS.

Forms transmembrane pores

A

SO

157
Q

SO or SS.

Strongly immunogenic

A

SO

158
Q

SO or SS.

Responsible for surface hemolysis

A

SS

159
Q

SO or SS.

Non-immunogenic

A

SS

160
Q

SO or SS.

Can be used serologically to titrate

A

SS

161
Q

Its titers are determined for the detection of previous or recent streptococcal pharyngeal infection

A

Anti-streptolysin O (ASO)

162
Q

Enzymes that act as spreading factors in Streptococcus spp

A

Hyaluronidase
Streptokinase (Fibrinolysin)
DNAse (Streptodornase)

163
Q

Spreading factor that splits hyaluronic acids in connective tissue

A

Hyaluronidase

164
Q

Spreading factor that dissolves fibrin clot

A

Streptokinase (Fibrinolysin)

165
Q

Spreading factor that depolymerizes viscous DNA in pus and is strongly immunogenic

A

DNAse (Streptodornase)

166
Q

True or False.

Streptolysin O is higher following pharyngeal infection while DNAse is higher following skin infection.

A

True

167
Q

Most dominant DNAse produced following skin infections

A

Anti-DNAse B

168
Q

True or False.

Titers of Anti- DNAse B are determined for the detection of previous or recent streptococcal skin infection

A

True

169
Q

True or False.

Anti-streptolysin O should be detected in pharyngeal infection.

A

True

170
Q

Habitat of GAS

A

Inhabits URT and skin of humans

171
Q

Transmission of GAS

A

Person to person by direct contact with mucosa or secretions (coughing, sneezing)
Fomites

172
Q

Clinical Disease of S. pyogenes

A 
Pharyngitis
Impetigo (pyoderma)
Erysipelas (St. Anthony’s Fire)
Cellulitis
Acute Bacterial Endocarditis
Puerperal Fever
Toxic Shock Syndrome-like
Necrotizing fascitis
Scarlet fever
173
Q

Most important clinical disease cause by S. pyogenes

A

Pharyngitis

174
Q

Associated with type A; non-bullous

Most cases begin with strep infection but staph replaces strep over time

A

Impetigo (pyoderma)

175
Q

Associated M types are frequently nephritogenic (may cause acute glomerulonephritis)
In pharyngeal infection – rheumatogenic

A

Impetigo (pyoderma)

176
Q

Peripherally spreading; hot, bright red, edematous, well circumscribed, sharply marginated lesions

A

Erysipelas

177
Q

Erysipelas most commonly affects

A

Face and legs

178
Q

Pattern of spread of Erysipelas

A

Spreads thru the lymphatic vessels

179
Q

Age group most commonly affected by Erysipelas

A

Common in infants, children and the elderly; accompanied by severe constitutional symptoms

180
Q

“flesh-eating bacteria”, “streptococcal gangrene” (requirement for aerobic conditions)

A

Necrotizing fascitis

181
Q

Highly destructive and potentially lethal infection of soft tissue (fatty tissues, fascia, muscles) and always follows trauma

A

Necrotizing fascitis

182
Q

Toxin the mediates necrotizing fascitis

A

ETB

183
Q

Toxin that mediates Scarlet Fever

A

ETA

184
Q

Scarlet colored (boiled lobster), body rashes (sandpaper-like), strawberry like tongue which evolves from tonsillar/pharyngeal focus

A

Scarlet Fever

185
Q

Laboratory diagnosis used for GAS

A 
Gram stain
Culture
Identification tests
Antigenic detection
Serology
186
Q

General characteristics of GAS in culture

A

Greyish white, transparent to translucent matte or glossy

187
Q

Glossy: ____________
Matte: ____________

A

Glossy: less M protein produced
Matte: more M protein produced

188
Q

Media used to culture GAS

A

BAP
Chocolate Agar
Selective media: CNA, PEA

189
Q

Tests used to identify GAS

A

Bacitracin disc test (TAXO A)

Pyroglutamic acid arylamidase test (PYR)

190
Q

Test used to differentiate S. pyogenes from other beta-hemolytic streptococci

A

Bacitracin Disc Test

191
Q

Test that is helpful in screening for group A strep in throat swab

A

Bacitracin disc test

192
Q

Results of bacitracin disc test

A

(+) any zone of inhibition (susceptible): Group A

193
Q

Diameter of zone of inhibition to be classifies as susceptible

A

10mm

194
Q

True or False.

S. pyogenes is the only beta-hemolytic streptococcus that is PYR (+)

A

True

195
Q

True or False.

Majority of Group A are PYR (+)

A

True

196
Q

Result of PYR test

A

(+): Bright pink/cherry red color in 1 minute

197
Q

Laboratory diagnostic that is based on reaction with monoclonal antibodies which reacts with group-specific carbohydrate antigen

A

Antigenic detection

198
Q

Laboratory diagnostic test that can be used in typing or detection of the organism in clinical specimens or in cultures (Group A-agglutination if it is Group A)

A

Antigenic detection

199
Q

Two types of serology testing for GAS

A

Anti-streptolysin O

Anti-DNAse B

200
Q

Serology test that is used to demonstrate previous or recent streptococcal infection, significantly following skin infections

A

Anti-DNAse B serology

201
Q

Prevention and control of GAS

A

Early detection and antimicrobial therapy

Treating carriers

202
Q

Replacing penicillin with other antibiotics is a risk factor for antibiotic resistance

A

Selection pressure

203
Q

Drug of choice for GAS

A

Penicillin

Microbiology and Parasitology (8 decks)

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