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Microbiology and Parasitology > Bacteria Associated With Skin Infections 2 > Flashcards

Bacteria Associated With Skin Infections 2 Flashcards

1
Q

Aerobic bacteria associated with skin infections

A

Erysipelothrix

Bacillus

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2
Q

Anaerobic bacteria associated with skin infections

A

Clostridium

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3
Q

Most important species of Erysipelothrix

A

Erysipelothrix rhusopathiae

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4
Q

General principles of Erysipelothrix rhusiopathiae

A 
Straight/slightly curved
Gram (+) rods in singles, short chains
V/L configuration 
Pleomorphic morphology 
Ubiquitous/abundant in nature 
Catalase negative
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5
Q

Determinants of pathogenicity of Erysipelothrix rhusiopathiae

A

Capsule
Hyaluronidase
Neuramidase/Sialidase

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6
Q

Pathogenic determinant that cleaves N-acetylneuraminic acid, the sialic acid on cell surface

A

Neuraminidase/Sialidase

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7
Q

Responsible for spread and invasion of E. rhusiopathiae

A

Hyaluronidase and neuraminidase

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8
Q

Transmission of E. rhusiopathiae

A

Subcutaneous inoculation through abrasion or puncture wounds

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9
Q

Portal of entry of E. rhusiopathiae

A

Skin (subcutaneous)

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10
Q

Site of inoculation of E. rhusiopathiae

A

Fingers and hands (usually like cellulitis)

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11
Q

Primary reservoir of E. rhusiopathiae

A

Pigs

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12
Q

Most common risk factor for E. rhusiopathiae infection

A

Occupational exposure

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13
Q

Clinical manifestations of E. rhusiopathiae

A

Erysipeloid
Diffuse cutaneous eruption with systemic symptoms (Uncommon)
Bacteremia associated with endocarditis

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14
Q

Clinical manifestation of E. rhusiopathiae among pigs

A

Erysipelas

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15
Q

Cause of Erysipelas in humans

A

S. pyogenes

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16
Q

Characteristics of erysipeloid

A

Non-suppurative, purplish erythematous lesions at site of inoculation
Lesions burn and itch
Local cellulitis

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17
Q

This manifestation of E. rhusiopathiae is due to tropism in aortic valve in systemic disease

A

Bacteremia associated with endocarditis

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18
Q

Laboratory diagnosis of E. rhusiopathiae

A

Gram stain
Culture
Mouse protection test

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19
Q

Specimens used to culture E. rhusipathiae

A

deep/full thickness aspirates or biopsies from margin of lesion

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20
Q

True or False.

Swabs are not appropriate because they are localized deep in tissues.

A

True

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21
Q

Media used to culture E. rhusiopathiae

A

Heart Infusion (HI) Broth
Blood Agar Plate (BAP)
Erysipelothrix Selective Broth (ESB)

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22
Q

Type of hemolysis caused by E. rhusipathiae

A

Alpha-hemolytic

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23
Q

CO2 requirement in growing E. rhusiopathiae

A

5-10% CO2

Capnophile

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24
Q

This differentiates Erysipelothrix from Corynebacterium and Listeria

A

Production of H2S

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25
Q

Confirmatory test for Erysipelothrix isolates

A

Mouse protection test

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26
Q

Principle behind mouse protection test

A

Test mouse is given equine hyperimmune E. rhusiopathiae antiserum for protection
Both control and test mice are inoculated with culture filtrate
After 5-6 days, the mouse without protection dies

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27
Q

General properties of Bacillus

A

Large, Gram (+) spore-forming rods in chains

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28
Q

General properties of Bacillus anthracis

A

Straight rods with square/truncate ends

Jointed “bamboo-rod” appearance

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29
Q

Bacillus or B. anthracis

Spores oval, centrally located and do not bulge/distend the cell

A

Both

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30
Q

Bacillus or B. anthracis

Encapsulated

A

B. anthracis

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31
Q

Bacillus or B. anthracis.

Spores are formed in culture, by dead/dying animals and not formed by living animals

A

B. anthracis

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32
Q

Bacillus or B. anthracis.

Non-motile

A

B. anthracis

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33
Q

Bacillus or B. anthracis.

Usually motile

A

Bacillus

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34
Q

Bacillus or B. anthracis.

Form rhizoid colonies with peripheral medusa head appearance

A

Bacillus

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35
Q

Determinants of pathogenicity of B. anthracis

A

Capsular polypeptide of D-glumatic acid

Anthrax toxin

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36
Q

Only organism to utilize protein (polypeptide of D-glutamic acid) for capsule

A

B. anthracis

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37
Q

Anti-phagocytic determinant of pathogenicity of B. anthracis

A

Capsular polypeptide of D-glutamic acid

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38
Q

Plasmid that encode for capsular polypeptide of D-glutamic acid

A

pXO2

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39
Q

“Invasive stage” of B. anthracis

A

Capsular polypeptide of D-glutamic acid

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40
Q

Capsular polypeptide of D-glutamic acid is detected by

A

Mac Fadyean reaction (polychrome methylene blue)

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41
Q

Major virulence factor for B. anthracis

A

Anthrax toxin

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42
Q

Characteristics of Anthrax toxin

A

Toxigenic stage
Heat-labile
Trimolecular toxin

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43
Q

Plasmid that encodes for Anthrax toxin

A

pXO1

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44
Q

Components of the Anthrax toxin

A 
Protective Ag (PA)
Edema Factor (EA)
Lethal Factor (LA)
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45
Q

Anthrax toxin component that delivers EA and LA to cytosol of cell

A

PA

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46
Q

Anthrax toxin component that activates the adenylyl cyclase

A

EA

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47
Q

Anthrax toxin component that is cytotoxic to cells and causes death of target cells

A

LA

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48
Q

True or False.

None of the three factors is toxic on their own.

A

True

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49
Q

PA + EA

A

Edema

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50
Q

PA + LA

A

Cytotoxicity

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51
Q

PA + EA + LA

A

Edema and cytotoxicity

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52
Q

Greatest threat from anthrax

A

The toxin it creates that destroys the victim’s cells even after antibiotics might have killed the bacteria itself.

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53
Q

Principal targets of Anthrax’s Toxin Attack are

A

Macrophages

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54
Q

Mechanism of macrophage attack during anthrax toxin attack

A

Anthrax bacteria flood into the bloodstream following
infection
Bacteria produce a toxin comprised of three parts
One part of the toxin, the protective antigen (PA), attaches to a receptor on the membrane, it penetrates the membrane allowing the other toxins to enter
Once inside, the other parts of the toxin kill the cell by disrupting its internal mechanisms

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55
Q

Infectious particle of B. anthracis

A

Spore

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56
Q

Disease of herbivores, meaning this is acquired from animals and humans are just accidental hosts

57
Q

True or False.

Anthrax transmission is only exogenous and not contagious because B. anthracis is not part of the normal flora of humans

58
Q

Human cases of anthrax

A

Agricultural

Industrial

59
Q

True or False.

There are no cases of person-to-person transmission of B. anthracis.

60
Q

Clinical manifestations of B. anthracis

A

Cutaneous (Malignant pustule)
Pulmonary (Woolsorter’s disease)
Gastrointestinal (Bowel anthrax)

61
Q

True or False.

Clinical manifestations of B. anthracis in humans reflects the mode of entry.

A

True.

Cutaneous - inoculation; most common
Pulmonary - inhalation; most lethal
GI - ingestion; common mode of entry for animals

62
Q

Epidemiology of Anthrax

A

Main reservoir of B. anthracis is the soil

Causes death of herbivores upon ingestion of contaminated vegetation

63
Q

Laboratory diagnosis of B. anthracis

A 
Gram stain
Culture and identification
Guinea Pig Lethality test
Serologic Test
PCR
64
Q

B. anthracis color of capsule after Mac Fadyean Reaction

A

Blue bacilli surrounded by red capsule

65
Q

More common stain used to identify B. anthracis

66
Q

Specimen used in culturing B. anthracis

A

Infected/dying animals

Material from pustule, if cutaneous

67
Q

Media used to culture B. anthracis

68
Q

Hemolytic pattern of B. anthracis

A

Non-hemolytic rhizoid colonies

69
Q

Test used to demonstrate characteristic appearance of B. anthracis

A

Guinea Pig Lethality test

70
Q

Most commonly used serologic test for B. anthracis

71
Q

Serologic tests performed for B. anthracis

A

Ascoli test
ELISA
IHA

72
Q

True or False.

Ascoli test lacks specificity for B. anthracis

73
Q

Confirmatory test for B. anthracis

74
Q

Treatment for B. anthracis

A

Penicillin (most commonly used), ciprofloxacin, doxycycline

75
Q

Prevention of anthrax

A

Control of disease in animals
Careful handling of infected animals/products
Vaccination

76
Q

B. anthracis for humans

A

Killed spore vaccine

Acellular (AVA, AVP)

77
Q

B. anthracis for animals with disease

A

Living spore vaccine

Stearne strain

78
Q

True or False.

Only occupationally at risk individuals are given killed spored vaccine.

79
Q

Anaerobes are unable to utilize O2 as finale electron acceptor because it lacks

A

Cyctochrome (for aerobic respiration)
Catalase (degrades H2O2)
SOD (degrades superoxide molecule)

80
Q

Most important enzyme to determine whether the organism can grow in the presence or absence of oxygen

81
Q

SOD
Present: _____________
Absent: ______________

A

Present: Aerobes and facultative anaerobes
Absent: Aerotolerant microbes

82
Q

Anarobes generate energy solely by

A

Fermentation

83
Q

Growth requirements of anaerobes

A

Low O2 tension (≤ 10% PO2)
Reduced Oxidation-reduction potential (Eh) - expressed in mV
>5% CO2
Enriched medium

84
Q

Features associated with anaerobic infections

A

Mostly caused by endogenous opportunistic pathogens
Occur in settings of compromised host defense
Usually not transmissible
Usually polymicrobic
Abscess formation and tissue necrosis
Develops slowly, many are chronic
Putrid odor of infected material/culture
Gas in tissues/loculations
(-) in aerobic cultures

85
Q

True or False.

Most anaerobic infections are from our own organisms.

86
Q

Putrid odor of infected material is due to

A

Production of short chain fatty acids as products of metabolism

87
Q

Reason behind crepitant cellulitis or gas gangrene

A

Gas in tissues/loculations

88
Q

Gives you a clue that the infection is cause by an anaerobic culture

A

(-) in aerobic culture

89
Q

Laboratory diagnosis for anaerobes

A

Gram stain

Culture and Identification

90
Q

Specimens used for anaerobic culture

A 
Sterile specimens
Abscess contents, deep wound aspirates
Blood, CSF, body fluids
Transtracheal aspirates
Urine (suprapubic, catheterized)
91
Q

Media used for anaerobic culture

A

Should contain reducing agents like sodium thiosulfate, Sodium bisulfate or Sodium sulfide

Egg Yolk Agar (EYA)
Chopped Meat Medium (Chlostridia)
Lake with Kanamycin and Vancomycin Blood Agar (LKVB; Bacteroides)

92
Q

Employed in LKVB to inhibit the growth of gram-positive organisms

A

Vancomycin

93
Q

Employed in LKVB to inhibit gram-negative facultatively anaerobic bacilli

94
Q

For furnish culture with reduced O2 and with the proper amount of CO2

A

Culture systems

95
Q

Culture systems used to grow anaerobes

A 
GasPak chamber (more common)
Anaerobic chamber (more advanced)
96
Q

Prevention of anaerobic infection

A

Avoid conditions that reduce Oxidation Reduction Potential in tissues to prevent anaerobiosis in deep tissues
Prevent introduction of anaerobes (from normal flora) into wounds, etc.
Protect against toxin, especially tetanus

97
Q

Bacteria that is widely distributed in nature, can be found in soil, sewage, and intestinal tracts of humans and other vertebrates

A

Clostridia

98
Q

Production of spores in Clostridia

A

Produced anaerobically, usually distend/bulge the cells

May either be terminal, subterminal, or central

99
Q

Clostridia or C. perfringens

Motile

A

Clostridia

100
Q

Clostridia or C. perfringens

Non-motile

A

C. perfringens

101
Q

General properties of C. perfringens

A

Short, plump Gram (+) rods with squarish ends or “boxcar appearance”
Aerotolerant
Encapsulated

102
Q

Characteristic of spores in Clostridium perfringens

A

Oval, central
Do not distend cell
Rarely observed

103
Q

True or False.

C. perfringens is part of the normal flora of GIT and female genital tract.

104
Q

Five type os C. perfringens

A

A, B, C, D and E based on production of specific toxins

105
Q

Most common types of C. perfringens

A

Type A and Type C (human diseases)

106
Q

Determinants of pathogenicity of C. perfringens

A

4 major lethal toxins - alpha, beta, epsilon, iota

107
Q

Major toxin of C. perfringens

A

Alpha toxin

108
Q

Toxin produces by all types of C. perfringens

A

Alpha toxin

109
Q

Component of alpha toxin that hydrolyzes phosphorylcholine in cell membrane causing lysis, therefore, death of the cell

A

Lecithinase C (Phospholipase C)

110
Q

Toxin produced by B and C

A

Beta toxin

111
Q

Toxin produced by types B and D

A

Epsilon toxin

112
Q

Toxin produced by type E

A

Iota toxin

113
Q

Toxins produced by type B

A

Alpha, Beta, Epsilon

114
Q

Toxins produced by type C

A

Alpha, Beta

115
Q

Toxins produced by type A

116
Q

Toxins produced by type D

A

Alpha, Epsilon

117
Q

Toxin produced by type E

A

Alpha, Iota

118
Q

Mode of transmission of C. perfringens

A

Simple wound contamination

Arises from exogenous and endogenous contamination

119
Q

Gas formation in soft tissues caused by C. perfringens

A

Crepitant cellulitis

120
Q

Highly lethal, necrotizing soft tissue infection of the skeletal muscle

A

Clostridial myonecrosis/gas gangrene

121
Q

Characteristics of Clostridial myonecrosis/gas gangrene

A 
Myonecrosis
Muscle swelling
Severe pain
Gas production
Sepsis
122
Q

True or False.

Clostridial myonecrosis/gas gangrene may be cause by C. perfringens, C. novyi, C. septicum.

123
Q

Analogy.
C. perfringens: _______________
C. septicum: _________________

A

C. perfringens: Traumatic gas gangrene

C. septicum: Non-traumatic gas gangrene

124
Q

Laboratory Diagnosis of traumatic gas gangrene

A

Gram stain

Culture

125
Q

Results of gram staining of traumatic gas gangrene

A

Predominance of Gram (+) positive rods
Sparse or no WBC
Leukostasis
Spores (rare)

126
Q

Reason behind sparseness or absence of WBC in traumatic gas gangrene

A

Alpha toxin hydrolyzes the cell membrane of WBCs

127
Q

Principle behind leukostasis

A

Stimulate platelet aggregation so that PMNs cannot penetrate infected tissues

128
Q

Specimens used to culture C. perfringens

A

Sterile materials only: tissues, aspirates, deep swabs

129
Q

Media used to culture C. perfringens

A

Chopped meat medium

130
Q

Biochemical methods to chracterize and identify C. perfringens

A 
Double Zone Hemolysis on BAP
Opalescence in EYA
Nagler reaction
Reverse cAMP
Stormy fermentation in milk
131
Q

Double-Zone Hemolysis on BAP is seen as

A

Inner zone: complete hemolysis

Outer zone: incomplete hemolysis

132
Q

Principle behind opalescence in EYA

A

Due to alpha toxin hydrolyzing the lecithin in egg yolk

133
Q

Confirmatory test for C. perfringens that uses specific antisera that inhibits alpha toxin causing the absence of opalescence

A

Nagler reaction

134
Q

Principle behind reverse cAMP

A

Beta-hemolysis when streaked with S. agalactiae

(+) result when an arrowhead hemolysis is observed towards the test organism

135
Q

Analogy. Identification of species
Simple cAMP test: _____________
Reverse cAMP test: _____________

A

Simple cAMP test: identify if culture is S. agalactiae

Reverse cAMP test: identify if culture is C. perfringens

136
Q

Analogy. Procedure.
Simple cAMP test: _____________
Reverse cAMP test: _____________

A

Simple cAMP test: Suspected S. agalactiae is streaked on medium and cross-streaked by S. aureus
Reverse cAMP test: Suspected C. perfringens is streaked on medium and cross-streaked with S. agalactiae

137
Q

Principle behind stormy fermentation in milk

A

Coagulated milk is disrupted due to gas production of C. perfringens

138
Q

Treatment for C. perfringens

A

Cleansing/surgical management of necrotic tissue
Antibiotic therapy: Penicillin, Clindamycin, Metronidazole
Hyperbaric oxygen (adjunct only)
Anti-toxin for α-toxin

139
Q

Prevention of C. perfringens

A

Early and adequate wound debridement
Wash with water to avoid anaerobic conditions
Prophylaxis (penicillin)

Microbiology and Parasitology (8 decks)

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