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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
Confirmatory test for Erysipelothrix isolates
Mouse protection test
26
Principle behind mouse protection test
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
27
General properties of Bacillus
Large, Gram (+) spore-forming rods in chains
28
General properties of Bacillus anthracis
Straight rods with square/truncate ends | Jointed “bamboo-rod” appearance
29
Bacillus or B. anthracis | Spores oval, centrally located and do not bulge/distend the cell
Both
30
Bacillus or B. anthracis | Encapsulated
B. anthracis
31
Bacillus or B. anthracis. | Spores are formed in culture, by dead/dying animals and not formed by living animals
B. anthracis
32
Bacillus or B. anthracis. | Non-motile
B. anthracis
33
Bacillus or B. anthracis. | Usually motile
Bacillus
34
Bacillus or B. anthracis. | Form rhizoid colonies with peripheral medusa head appearance
Bacillus
35
Determinants of pathogenicity of B. anthracis
Capsular polypeptide of D-glumatic acid | Anthrax toxin
36
Only organism to utilize protein (polypeptide of D-glutamic acid) for capsule
B. anthracis
37
Anti-phagocytic determinant of pathogenicity of B. anthracis
Capsular polypeptide of D-glutamic acid
38
Plasmid that encode for capsular polypeptide of D-glutamic acid
pXO2
39
“Invasive stage” of B. anthracis
Capsular polypeptide of D-glutamic acid
40
Capsular polypeptide of D-glutamic acid is detected by
Mac Fadyean reaction (polychrome methylene blue)
41
Major virulence factor for B. anthracis
Anthrax toxin
42
Characteristics of Anthrax toxin
Toxigenic stage Heat-labile Trimolecular toxin
43
Plasmid that encodes for Anthrax toxin
pXO1
44
Components of the Anthrax toxin
``` Protective Ag (PA) Edema Factor (EA) Lethal Factor (LA) ```
45
Anthrax toxin component that delivers EA and LA to cytosol of cell
PA
46
Anthrax toxin component that activates the adenylyl cyclase
EA
47
Anthrax toxin component that is cytotoxic to cells and causes death of target cells
LA
48
True or False. | None of the three factors is toxic on their own.
True
49
PA + EA
Edema
50
PA + LA
Cytotoxicity
51
PA + EA + LA
Edema and cytotoxicity
52
Greatest threat from anthrax
The toxin it creates that destroys the victim’s cells even after antibiotics might have killed the bacteria itself.
53
Principal targets of Anthrax’s Toxin Attack are
Macrophages
54
Mechanism of macrophage attack during anthrax toxin attack
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
55
Infectious particle of B. anthracis
Spore
56
Disease of herbivores, meaning this is acquired from animals and humans are just accidental hosts
Anthrax
57
True or False. | Anthrax transmission is only exogenous and not contagious because B. anthracis is not part of the normal flora of humans
True
58
Human cases of anthrax
Agricultural | Industrial
59
True or False. | There are no cases of person-to-person transmission of B. anthracis.
True
60
Clinical manifestations of B. anthracis
Cutaneous (Malignant pustule) Pulmonary (Woolsorter’s disease) Gastrointestinal (Bowel anthrax)
61
True or False. | Clinical manifestations of B. anthracis in humans reflects the mode of entry.
True. Cutaneous - inoculation; most common Pulmonary - inhalation; most lethal GI - ingestion; common mode of entry for animals
62
Epidemiology of Anthrax
Main reservoir of B. anthracis is the soil | Causes death of herbivores upon ingestion of contaminated vegetation
63
Laboratory diagnosis of B. anthracis
``` Gram stain Culture and identification Guinea Pig Lethality test Serologic Test PCR ```
64
B. anthracis color of capsule after Mac Fadyean Reaction
Blue bacilli surrounded by red capsule
65
More common stain used to identify B. anthracis
India ink
66
Specimen used in culturing B. anthracis
Infected/dying animals | Material from pustule, if cutaneous
67
Media used to culture B. anthracis
BAP
68
Hemolytic pattern of B. anthracis
Non-hemolytic rhizoid colonies
69
Test used to demonstrate characteristic appearance of B. anthracis
Guinea Pig Lethality test
70
Most commonly used serologic test for B. anthracis
ELISA
71
Serologic tests performed for B. anthracis
Ascoli test ELISA IHA
72
True or False. | Ascoli test lacks specificity for B. anthracis
True
73
Confirmatory test for B. anthracis
PCR
74
Treatment for B. anthracis
Penicillin (most commonly used), ciprofloxacin, doxycycline
75
Prevention of anthrax
Control of disease in animals Careful handling of infected animals/products Vaccination
76
B. anthracis for humans
Killed spore vaccine | Acellular (AVA, AVP)
77
B. anthracis for animals with disease
Living spore vaccine | Stearne strain
78
True or False. | Only occupationally at risk individuals are given killed spored vaccine.
True
79
Anaerobes are unable to utilize O2 as finale electron acceptor because it lacks
Cyctochrome (for aerobic respiration) Catalase (degrades H2O2) SOD (degrades superoxide molecule)
80
Most important enzyme to determine whether the organism can grow in the presence or absence of oxygen
SOD
81
SOD Present: _____________ Absent: ______________
Present: Aerobes and facultative anaerobes Absent: Aerotolerant microbes
82
Anarobes generate energy solely by
Fermentation
83
Growth requirements of anaerobes
Low O2 tension (≤ 10% PO2) Reduced Oxidation-reduction potential (Eh) - expressed in mV >5% CO2 Enriched medium
84
Features associated with anaerobic infections
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
True or False. | Most anaerobic infections are from our own organisms.
True
86
Putrid odor of infected material is due to
Production of short chain fatty acids as products of metabolism
87
Reason behind crepitant cellulitis or gas gangrene
Gas in tissues/loculations
88
Gives you a clue that the infection is cause by an anaerobic culture
(-) in aerobic culture
89
Laboratory diagnosis for anaerobes
Gram stain | Culture and Identification
90
Specimens used for anaerobic culture
``` Sterile specimens Abscess contents, deep wound aspirates Blood, CSF, body fluids Transtracheal aspirates Urine (suprapubic, catheterized) ```
91
Media used for anaerobic culture
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
Employed in LKVB to inhibit the growth of gram-positive organisms
Vancomycin
93
Employed in LKVB to inhibit gram-negative facultatively anaerobic bacilli
Kanamycin
94
For furnish culture with reduced O2 and with the proper amount of CO2
Culture systems
95
Culture systems used to grow anaerobes
``` GasPak chamber (more common) Anaerobic chamber (more advanced) ```
96
Prevention of anaerobic infection
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
Bacteria that is widely distributed in nature, can be found in soil, sewage, and intestinal tracts of humans and other vertebrates
Clostridia
98
Production of spores in Clostridia
Produced anaerobically, usually distend/bulge the cells | May either be terminal, subterminal, or central
99
Clostridia or C. perfringens | Motile
Clostridia
100
Clostridia or C. perfringens | Non-motile
C. perfringens
101
General properties of C. perfringens
Short, plump Gram (+) rods with squarish ends or “boxcar appearance” Aerotolerant Encapsulated
102
Characteristic of spores in Clostridium perfringens
Oval, central Do not distend cell Rarely observed
103
True or False. | C. perfringens is part of the normal flora of GIT and female genital tract.
True
104
Five type os C. perfringens
A, B, C, D and E based on production of specific toxins
105
Most common types of C. perfringens
Type A and Type C (human diseases)
106
Determinants of pathogenicity of C. perfringens
4 major lethal toxins - alpha, beta, epsilon, iota
107
Major toxin of C. perfringens
Alpha toxin
108
Toxin produces by all types of C. perfringens
Alpha toxin
109
Component of alpha toxin that hydrolyzes phosphorylcholine in cell membrane causing lysis, therefore, death of the cell
Lecithinase C (Phospholipase C)
110
Toxin produced by B and C
Beta toxin
111
Toxin produced by types B and D
Epsilon toxin
112
Toxin produced by type E
Iota toxin
113
Toxins produced by type B
Alpha, Beta, Epsilon
114
Toxins produced by type C
Alpha, Beta
115
Toxins produced by type A
Alpha
116
Toxins produced by type D
Alpha, Epsilon
117
Toxin produced by type E
Alpha, Iota
118
Mode of transmission of C. perfringens
Simple wound contamination | Arises from exogenous and endogenous contamination
119
Gas formation in soft tissues caused by C. perfringens
Crepitant cellulitis
120
Highly lethal, necrotizing soft tissue infection of the skeletal muscle
Clostridial myonecrosis/gas gangrene
121
Characteristics of Clostridial myonecrosis/gas gangrene
``` Myonecrosis Muscle swelling Severe pain Gas production Sepsis ```
122
True or False. | Clostridial myonecrosis/gas gangrene may be cause by C. perfringens, C. novyi, C. septicum.
True
123
Analogy. C. perfringens: _______________ C. septicum: _________________
C. perfringens: Traumatic gas gangrene | C. septicum: Non-traumatic gas gangrene
124
Laboratory Diagnosis of traumatic gas gangrene
Gram stain | Culture
125
Results of gram staining of traumatic gas gangrene
Predominance of Gram (+) positive rods Sparse or no WBC Leukostasis Spores (rare)
126
Reason behind sparseness or absence of WBC in traumatic gas gangrene
Alpha toxin hydrolyzes the cell membrane of WBCs
127
Principle behind leukostasis
Stimulate platelet aggregation so that PMNs cannot penetrate infected tissues
128
Specimens used to culture C. perfringens
Sterile materials only: tissues, aspirates, deep swabs
129
Media used to culture C. perfringens
Chopped meat medium
130
Biochemical methods to chracterize and identify C. perfringens
``` Double Zone Hemolysis on BAP Opalescence in EYA Nagler reaction Reverse cAMP Stormy fermentation in milk ```
131
Double-Zone Hemolysis on BAP is seen as
Inner zone: complete hemolysis | Outer zone: incomplete hemolysis
132
Principle behind opalescence in EYA
Due to alpha toxin hydrolyzing the lecithin in egg yolk
133
Confirmatory test for C. perfringens that uses specific antisera that inhibits alpha toxin causing the absence of opalescence
Nagler reaction
134
Principle behind reverse cAMP
Beta-hemolysis when streaked with S. agalactiae | (+) result when an arrowhead hemolysis is observed towards the test organism
135
Analogy. Identification of species Simple cAMP test: _____________ Reverse cAMP test: _____________
Simple cAMP test: identify if culture is S. agalactiae | Reverse cAMP test: identify if culture is C. perfringens
136
Analogy. Procedure. Simple cAMP test: _____________ Reverse cAMP test: _____________
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
Principle behind stormy fermentation in milk
Coagulated milk is disrupted due to gas production of C. perfringens
138
Treatment for C. perfringens
Cleansing/surgical management of necrotic tissue Antibiotic therapy: Penicillin, Clindamycin, Metronidazole Hyperbaric oxygen (adjunct only) Anti-toxin for α-toxin
139
Prevention of C. perfringens
Early and adequate wound debridement Wash with water to avoid anaerobic conditions Prophylaxis (penicillin)

Microbiology and Parasitology (8 decks)

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