Skin- Bacteria Flashcards

1
Q

What gram stain is Staph Aureus

A

+

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2
Q

Is Staph Aureus thick or thin walled

A

Thick

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3
Q

Where are the granulocytes for Staph Aureus found

A

Intracellularly

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4
Q

What hemolytic is Staph Aureus

A

Beta

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5
Q

What kind of agar does Staph Aureus grow on

A

Blood agar

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6
Q

Is Staph Aureus aerobic or anerobic

A

Aerobic

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7
Q

What color colonies does Staph Aureus grow

A

White, becomes yellow with age

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8
Q

What catalase and coagulase is S. Aureus

A

Positive

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9
Q

Is Staph Aureus found normally on the body

A

Yes found in anterior nares for 30% of population

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10
Q

What is the mechanism of escape for Staph Aureus

A

Staph in general is coated with fibrin, makes it resistant to phagocytosis

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11
Q

What are other biologically active substances in Staph Aureus

A
Hemolysins 
Hyaluronidase 
Nuclease
Lipase
Protease
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12
Q

What is the toxin found in S. Aureus

A

Alpha toxin (Cytotoxin)

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13
Q

What is the action of the toxin found in S. Aureus

A

Causes necrosis/ Death
Membranes leak
Causes RBCs to lyse

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14
Q

What kind of toxin is Panton- Valentine Leukocidin

A

Cytotoxin

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15
Q

What is the action of Panton Valentine Leukocidin

A

Lyses neutrophils, damages host cells

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16
Q

What diseases are associated with Panton Valentine Leukocidin

A

Pneumonia
Skin Infections
MRSA

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17
Q

What is the virulence of S. Aureus

A

10^5- 10^6 to start infection

10^ 2 if a suture is present

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18
Q

How does Staph cellulitis act?

A

Alternates btwn walling off and rapid extension of infection

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19
Q

What is a furuncle what infection causes it

A

Boil in hair follicle
Can give rise to stye
Staph

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20
Q

Where are carbuncles mostly found?

A

Back of the neck, formed from furuncle

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21
Q

What causes Chronic furunculosis

A

Delayed hypersensitivity to staphylococcal

Responsible for inflammation and necrosis

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22
Q

What disease is chronic staph associated with

A

Chronic granulomatous Dx

Diabetes

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23
Q

Impetigo is a bacterial infection composed of what

A

S. Aureus, 30% of the time found with streptococci

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24
Q

What is bullous impetigo

A

Caused by S. Aureus, causes skin to exfoliate.

Blisters contain many staphylococci

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25
Q

Where do the majority of wound infections come from

A

S. Aureus.
Patients own strain
Hospital acquired

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26
Q

When do you find Staphylococcal pneumonia

A

Secondary to another lung injury: influenza, aspiration

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27
Q

What causes scalded skin syndrome

A

S. Aureus

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28
Q

How does Scalded skin present

A

Toxin absorbed into blood causing erythema and intraepidermal desquamation

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29
Q

What causes Exfoliatins?

A

S. Aureus

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30
Q

How does exfoliatins present?

A

Intercellular splitting of epidermis
Split between Statum Spinosum and stratum granulosum
Disruption of intercellular junctions

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31
Q

What infection causes toxic shock

A

S. Aureus

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32
Q

What are some signs of toxic shock

A

Rash

Strawberry tongue

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33
Q

How is rash from toxic shock differ from scalded skin syndrome

A

Rash develops then desquamation at deeper levels than scalded skin syndrome

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34
Q

Pyrogenic exotoxin

A

Toxic shock syndrome toxin 1
Stimulates cytokines
Direct toxic effect on endothelial cells

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35
Q

Pathogenicity of Pyrogenic exotoxin

A

Similar to exotoxin of Group A strep

Stimulates enhanced T lymphocytes

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36
Q

Treatment for S. Aureus

A

Methicillin

Many strains resistant: MRSA

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37
Q

What is the difference between hospital and community acquired MRSA

A

Community acquired is susceptible to clindamycin, also carries PVL toxin

Typically an uncomplicated skin infection. needs incision and drainage

38
Q

Where is coagulase negative staphlococci usually found?

A

Skin, anterior nose

39
Q

What do coagulase neg staphlococci have for virulence factors

A

Lacks major virulence factors

Not beta hemolytic

40
Q

What are the characteristics of S. Iugdunesis

A

Coagulase negative
Cuases infections similar to S. Aureus
Forms abcesses

41
Q

What is the virulence factor for S. Epidermidis

A

Produces extracell polysaccharide slime/biofilm

Protects it from phagocytosis, antibiotics

42
Q

What is the clinical significance of coagulase neg staph

A

Normal flora

Need to collect deep invasive samples

43
Q

When is coagulase neg staph detection significant

A

If intracellular gram + cocci are seen in gram stain

44
Q

Where is coagulase neg staph usually found

A

On implants

45
Q

Characteristics of streptococci

A

Normal flora
Found in mouth
GI
Gram + cocci/ chains

46
Q

Characteristics of pyogenic streptococci

A

Beta hemolytic

Causes purulent infections

47
Q

What kind of toxin is released by Group A toxin

A

Pyrogenic exotoxin (SPE)

48
Q

What are the effects of SPE (pyrogenic exotoxin )

A

Stimulates cytokine release

Red rash on skin- scarlet fever

49
Q

Pharyngitis is found in which strep

A

Group A

50
Q

How does Group A strep phryngitis spread

A

Direct contact or aerosols

51
Q

Scarlet fever has what characteristics

A

Strawberry tongue
Sandpaper rash
Deep red color cheeks
Punctate hemorrhages on palates

52
Q

What is a complication for post strep

A
Acute Rheumatic fever 
Acute glomerulonephritis (antigen/antibody complex in kidneys)
53
Q

Characteristics of Impetigo

A

Group A strep infection of skin

Glomerulonephritis is a complication

54
Q

Difference between cellulitits and erysipelas

A

Cellulitis- deep dermis rash with fever (s. Aureus)
Erysipelas- upper dermis (Group A >C,G)
Both are beta hemolytic

55
Q

Erysipelas presentation

A

Group A strep infection of upper dermis

Typically on face

56
Q

Necrotizing fascitis is typically seen where

A

Beta hemolytic group A Streptococcus

57
Q

Vascular compromise can be seen in what

A

Strep A TSS

58
Q

How to diagnose Beta Streptococcus infections

A

Gram Stain
Blood cultures
Wound cultures

59
Q

Human bites related to which infections

A

Group A strep infections

60
Q

Which strep is known for deep tissue abscesses

A

S. Milleri

61
Q

What causes dental caries

A

S. Mutans (viridan species)

62
Q

Nutitionally deficient streptococci

A

Abiotrophia

63
Q

What is needed to grow abiotrophia?

A

Vitamin or nutrients from other bacteria/ human cells
Causes bacterial endocarditis
Need to add feeder colony

64
Q

what kind of hemolytic strep is enteroccus

A

non-hemolytic strep

65
Q

Which corynebacterium is related to skin infections

A

Corynebacterium ulcerans

66
Q

Which corynebacterium is related to nosocomial blood and wound infections

A

Corynebacterium jeikeium

67
Q

Characteristics of Erysipelothrix Rhusiopathiae

A

Gram +, found in animals meat and seafood

68
Q

Characteristics of Erysipeloid

A

Slow spreading skin infection
Found in fishermen, butchers, vets
Tx penicillin

69
Q

Characteristics of anaerobic infections

A

Mixed gram + and -

70
Q

Where are anaerobes normally found on human body

A

Stool of colon
Mouth
Vagina
Sebaceuous gland

71
Q

When do anaerobes attack

A

After tissue trauma/injury

72
Q

How to collect anaerobes in culture

A

Abscess aspirate
Surgically removed tissue
Blood

73
Q

Characteristics of clostridium perfringens

A
Gram + 
Spore forming rods 
Fast growing anaerobic fermenter (generates H2 and CO2)
Encapsulated/ non motile 
Found in colon and soil
74
Q

What are the culture characteristics of Clostridium perfringens

A

Double zone hemolysis (blood agar)

Litmus milk stormy fermentation

75
Q

What are the toxins associated with clostridium perfringens

A

Alpha: Main pathogenic factor- causes necrosis
Theta: Toxic for heart muscle/ capillaries (similar to streptolysin O in beta strep)
Enterotoxin: food poisoning

76
Q

Clinical presentation of C. Perfringens

A
Gas necrosis ( crepitation ) 
Destruction of collagenase
DNAse 
Hyaluronidase 
Protease
77
Q

Where does C. Perfringens occur?

A

Traumatic wounds

78
Q

What kind of diagnosis is gas gangrene

A

clinical diagnosis

79
Q

How is anaerobic cellulitis different from other forms of cellulitis

A

Less pain and swelling

80
Q

What would be seen with a dog bite

A

Anaerobic cellulitis

Mixed anaerobic flora

81
Q

Pathogenic non-sporeforming gram + anaerbic rods

A

Actinomyces

Propionibacterium

82
Q

Less pathogenic non-sporeforming gram + anaerobic rods

A

Mobiluncus (vaginitis)
Lactobacillus
Eubacterium
Rothia

83
Q

Characteristics of actinomyces

A

Long Gram + rods
Branching
no spores/ not acid fast
Sulphur granules

84
Q

Most common actinomycetes

A

A. Israelii

Mouth infection 4-10 days to grow

85
Q

Where does actinimyses usually colonize

A

Mouth, Pneumonia, neck/head

86
Q

Characteristics of Propionibacterium

A

Anaerobe
Gram +, non-sporeforming rods
Part of normal skin flora

87
Q

What is the most common gram neg rod causing anaerobic infections

A

Bacteroides Fragilis

88
Q

Louse borne typhus fever is from what

A

Rickettsia Prowazekii

89
Q

Characteristics of typhus fever

A

Rash 10 days after illness

Comprises circulation

90
Q

Lab diagnosis for Rickettsia

A

Culture difficult
PCR best
Immuno assays for antibody

91
Q

Classic lyme disease

A

Tick bite-> spirochete
Erythema chromicum migrans
Constitutional sx for months
Meningeal irritation

92
Q

Diagnosis of burgdorferi

A

EIA antibody/ western

Enzyme immuno assay