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BMR 607 Final > Bacterial Skin Infection > Flashcards

Bacterial Skin Infection Flashcards

1
Q

Primary skin Lesions?

A
  • Macules and Patches
  • Papules and Plaques
  • Vesicles
  • Bulla
  • Pustule
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2
Q

Describe Macules and Patches

A

Flat lesions

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3
Q

Describe Papules and Plaques?

A

Raised lesions, occur in many forms and can be caused by (Bartonella henselae [cat scratch fever])

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4
Q

Describe Vesicles?

A

Fluid-filled lesions (<1 cm) due to proliferation of organisms, usually viruses within the epidermis.

  • VZV, HSV, coxsackievirus, pox, Ricketsia.
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5
Q

Describe bulla?

A
  • Fluid-filled lesions (>1cm)
  • Staphylococcal scalded skin syndrome (S. Aureus)
  • Necro fasciitis
  • Gas gangrene
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6
Q

Describe Pustule?

A

Pus-filled vesicles, usually with white center.

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7
Q

List Secondary Skin lesions?

A
  • Erosion
  • Ulcers
  • Crust
  • Folliculitis
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8
Q

Describe the difference between erosion and ulcers?

A

Erosion = epidermis lesion

Ulcer = epidermis + dermis lesion

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9
Q

Describe Ulcers?

A
  • Can occur with or without eschars.
  • Can be caused by:
    • cutaneous anthrax
    • ulceroglandular tularemia
    • plague
    • mycobacterial infection
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10
Q

Describe crust?

A
  • Dried exudate
    • S. Aureus usually starts with a bullous phase before developing a golden-brown crust (“Honey-colored crust”)
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11
Q

Describe Folliculitis?

A

Localized infection of hair follicles is usually due to S. Aureus “hot-tub folliculitis” is a diffuse condition caused by pseudomonas aeruginosa.

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12
Q

Acute inflammation is the same as?

A

Edema and neutrophils in the tissue

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13
Q

Chronic inflammation is what?

A

The accumulation of lymphocytes/

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14
Q

Acute inflammation is caused by two types of stimuli?

A

Infections and tissue necrosis.

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15
Q

What are the major cells that regulate the intensity of acute inflammation?

A

Macrophages

Neutrophils

Mast Cells

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16
Q

What are the 4 neutrophil chemotactic factors?

A

C5a

IL-8

Leukotriene B4 (LTB4)

Bacterial Products

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17
Q

Where does extravasation occur?

A

Post-capillary venules

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18
Q

What are the 4 steps of Extravasation?

A
  1. Margination & rolling
  2. Tight binding
  3. Diapedesis (transmigration)
  4. Migration
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19
Q

In Margination & Rolling: Histamines induce P-selectin of what cells?

A

Endothelial cells (Weibel-Palade bodies)

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20
Q

In Margination & Rolling: E-selectin of endothelial cells is induced by what?

A

TNFa and IL-1 (macs)

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21
Q

In Margination & Rolling: Selectins bind where?

A

Selectins bind to Sialyl-Lewis X (SLex) on Leukocytes.

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22
Q

In the Tight Binding (second) stage of Extravasation: Integrins of ____(1)____, upregulated by _____(2)_____, bind to adhesion molecules (ICAM-1 and VCAM-1) on _____3____.

A
  1. PMNs
  2. C5a and LTB4
  3. Endothelial Cells
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23
Q

Tissue Macrophages associated with Skin:

A

Langerhans cells

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24
Q

Tissue Macrophages associated with Liver:

A

Kupffer Cells

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25
Q

Tissue Macrophages associated with Bone:

A

Osteoclast

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26
Q

Tissue Macrophages associated with Brain-CNS:

A

Microglial

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27
Q

Staphylococcal Scalded Skin Syndrome (SSSS, Ritter’s Disease) is treated with what?

A
  • Pain Management
  • Bacterimia rare.
  • Nafcillin
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28
Q

Staphylococcal Scalded Skin Syndrome (SSSS, Ritter’s Disease):

Major symptom/sign

A
  • Perioral erythema covers entire body within-2 days of positive.
  • Nikolsky’s sign - large blister with clear fluid, no organism, no leucocytes.
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29
Q

Staphylococcal Scalded Skin Syndrome (SSSS, Ritter’s Disease):

Exfoliative toxins A or B are? allowing them to do what?

A
  • Serine Proteases
  • Cleave Desmosomal cadherins in the stratum granulosum layer.
    • Desmosomes are cell-cell junctions.
30
Q

Describe Pemphigus Vaguaris?

A
  • Autoimmune destruction of desmosomes between keratinocytes.
  • IgG antibody destruction of desmoglein.
  • Skin and mucosal bullae
  • Tombstone appearance.
31
Q

Skin abscesses, furuncles, and carbuncles are all related to what?

A

Hair Follicle

32
Q

Skin abscesses, furuncles, and carbuncles: Common complication

A

Liqueficative necrosis - typical of bacteria infections, due to the hydrolytic enzymes carried out by neutrophils.

33
Q

Skin abscesses, furuncles, and carbuncles: Main bacterial cause?

A

S. Aureus occurs in 50% of cases

34
Q

Skin abscesses, furuncles, and carbuncles: How to treat minor and major?

A

Minor: Warm compress to aid drainage

Major: Incision and drainage.

35
Q

What are the six types of necrosis?

A
  1. Coagulative
  2. Liquefactive
  3. Caseous
  4. Fat
  5. Fibrinoid
  6. Gangrenous
36
Q

Where is Coagulative necrosis not observed?

A
  • Infarcts/ischemia in most tissues except for brain, kidney, heart, and adrenal glands.
37
Q

Unique feature of coagulative necrosis?

A

Denature enzymes, no proteolysis.

38
Q

Describe Liquefactive necrosis: Common occurrence, mechanism, and severe negative outcome.

A
  • Bacterial abscesses/brain infarcts
  • Neutrophils release lysosomal enzymes
  • Continuous presence causes Brain Cavitation.
39
Q

Describe the three mentioned causes of Caseous Necrosis and mech.

A
  • TB, Systemic fungi, nocardia
  • Macs wall of bacteria, debris surrounded by lymphocytes and activated macrophages (granuloma).
40
Q

Describe Fat Necrosis?

A
  • Acute pancreatitis (Enzymatic).
  • Lipase breaks down triglycerides → fatty acids binds to calcium → saponification
41
Q

Describe Fibrinoid necrosis:

A
  • Autoimmune vascular reaction
    • Type 3 hypersensitivity or plasma protein fibrin leakage.
  • Thick and pink vessel walls
42
Q

Describe Gangrenous necrosis:

A
  • Distal extremity and GI tract, after chronic Ischemia
  • Dry ischemia (coagulative)
  • Wet: superinfection (liquefactive superimposed on coagulative).
43
Q

Non-Bullous impetigo (pyoderma, impetigo contagiosa)

A
  • Contagious, common in children
    • Honey-colored crusted lesions
    • Dried exudate.
  • Commonly caused by S. Aureus
    • Second most common is S. pyogenes.
  • Therefore antibiotic must cover both.
    • Topical therapy (Mupirocin + retapamulin)
  • Nephrogenic GAS can lead to post-strep glomerulonephritis.
44
Q

Bullous impetigo

A
  • Caused by S. Aureus of group 2 that produces Exfoliative toxin A (no direct bacterial colonization).
    • Causes loss of cell adhesion by targeting desmoglein 1.
      • Target antigen in majority of the cases linked to IgG/IgA pemphigus. (Autoimmune)
  • No Nikolsky’s sign
45
Q

What is Ecthyma?

A
  • A variant of impetigo on the lower extremities causing punched-out ulcerative lesions.
    • Yellow crusts extending into the dermis
      • Can be cultured and gram stain is positive for staph or strep.
46
Q

Describe Erysipelas?

A
  • Infection spread in: Upper dermis and superficial lymphatics
    • Deeper dermis or fat is called cellulitis.
  • Rash is normally sharply demarcated from the surrounding, normal skin.(5-20% facial).
  • Always caused by GAS.
47
Q

Symptoms of Cellulitis?

A

Redness, induration, heat, tenderness, and the distinction between infected and noninfected area is not as clear.

48
Q

Cellulitis in unimmunized children is often caused by?

A

H. influenzae type B.

49
Q

Cellulitis is 90% caused by?

A

GAS and S. Aureus.

50
Q

Cellulitis associated with bites or scratches from cats and dogs?

A

P. multocida

51
Q

Cellulitis development?

A

Rapid (24 to 48 hours) from minor injury to severe septicemia.

52
Q

P. aeruginosa infection of Burn wounds? Mechanism?

A
  • Vascular damage, tissue necrosis, and bacteremia prevent neutrophils from being able to penetrate into the wounded area resulting in severe infection.
53
Q

Describe Infectious folliculitis?

A
  • “Hot tub”
  • Caused by P. aeruginosa
  • resolves in 7 to 10 days
54
Q

Describe Type 1 Necrotizing Fasciitis?

A
  • Mixed microbial infection caused by both aerobic and anaerobic bacteria.
  • Common after surgical procedures in patients with diabetes and peripheral vascular disease.
55
Q

Describe Type 2 Necrotizing fasciitis?

A

A mono-microbial infection caused by group A steptococcus (GAS, S. pyogenes) and MRSA.

56
Q

Necrotizing fasciitis caused by halophilic V. vulnificus?

A

Rapid progressive wound infections after exposure to contaminated sea water.

50% mortality.

57
Q

Necrotizing infections of muscle:

A
  • Myonecrosis
  • Gas is always found in the skin, but fascia and deep muscle spared.
    • 50% of cases where necro fasciitis is caused by GAS.
58
Q

Cutaneous Anthrax

A
  • Most human cases come from working with animals.
  • Progress to an ulcer surrounding vesicles. Necrotic eschar
  • Round black lesion with a rim of edema.
    • Malignant pustule.
59
Q

Cutibacterium (Propionibacterium) acnes

A
  • Gram positive
  • Aerotolerant anaerobe
  • Acne in young males
    • androgen receptors on sebaceous glands
    • Cutibacterium infection produces lipases that digest sebum and release pro-inflammatory fatty acids.
      *
60
Q

Treatment of Cutibacterium acnes?

A

Benzoyl peroxide (antimicrobial) and Vitamin A derivatives which reduces keratin production

61
Q

Describe Cat scratch disease?

A
  • B. henselae
  • Papule at infection site.
  • Noncaseating granuloma with pus (B. henselae with neutrophils).
62
Q

Describe Trench Fever:

A
  • B. quintana:
  • Homeless and HIV positive
  • Relapsing fever, severe headache and leg pain.
63
Q

4 Common disease caused by Bartonella

A
  1. Cat scratch disease
  2. Trench fever
  3. Septicemia
  4. Endocarditis: (occurs in 20%).
64
Q

Describe Bacillary Angiomatosis

A
  • AKA, epithelioid angiomatosis
    • In HIV positive
  • Blood vessel proliferation → tumor-like masses, nodules, or purple papules in skin and organs. Similar to Kaposi’s sarcoma.
65
Q

Treatment of Bacillary angiomatosis?

A

Erythromycin, doxycycline, or tetracycline.

66
Q

Toxic shock syndrome: (TSS)

A
  • Cutaneous and soft tissue involvement
  • Different from septic shock in diarrhea.
  • Caused by Toxic shock syndrome toxin-1 (TSST-1) of S. aureus and is a super-antigen.
67
Q

Describe Meningococcemia?

A
  • Petechial macules on the lower extremity
    • Can be Rocky Mountain spotted fever or West nile virus.
68
Q

Describe Disseminated gonococcal infection?

A

Tender, hemorrhagic, and necrotic pustules on the fingers and palms.

69
Q

Describe Ecthyma gangrenosa?

A
  • Ulcerative form of impetigo
  • Caused by P. aeruginosa bacteremia.
    • Occurs in neutropenic patients.
70
Q

What are the major cells that regulate the intensity of acute inflammation?

A

Macrophages

Neutrophils

Mast Cells

71
Q

Describe bulla?

A
  • Fluid-filled lesions (>1cm)
  • Staphylococcal scalded skin syndrome (S. Aureus)
  • Necro fasciitis
  • Gas gangrene

BMR 607 Final (10 decks)

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