Bacterial Skin Infection Flashcards
(71 cards)
1
Q
Primary skin Lesions?
A
- Macules and Patches
- Papules and Plaques
- Vesicles
- Bulla
- Pustule
2
Q
Describe Macules and Patches
A
Flat lesions
3
Q
Describe Papules and Plaques?
A
Raised lesions, occur in many forms and can be caused by (Bartonella henselae [cat scratch fever])
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.
5
Q
Describe bulla?
A
- Fluid-filled lesions (>1cm)
- Staphylococcal scalded skin syndrome (S. Aureus)
- Necro fasciitis
- Gas gangrene
5
Q
Describe bulla?
A
- Fluid-filled lesions (>1cm)
- Staphylococcal scalded skin syndrome (S. Aureus)
- Necro fasciitis
- Gas gangrene
6
Q
Describe Pustule?
A
Pus-filled vesicles, usually with white center.
7
Q
List Secondary Skin lesions?
A
- Erosion
- Ulcers
- Crust
- Folliculitis
8
Q
Describe the difference between erosion and ulcers?
A
Erosion = epidermis lesion
Ulcer = epidermis + dermis lesion
9
Q
Describe Ulcers?
A
- Can occur with or without eschars.
- Can be caused by:
- cutaneous anthrax
- ulceroglandular tularemia
- plague
- mycobacterial infection
10
Q
Describe crust?
A
-
Dried exudate
- S. Aureus usually starts with a bullous phase before developing a golden-brown crust (“Honey-colored crust”)
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.
12
Q
Acute inflammation is the same as?
A
Edema and neutrophils in the tissue
13
Q
Chronic inflammation is what?
A
The accumulation of lymphocytes/
14
Q
Acute inflammation is caused by two types of stimuli?
A
Infections and tissue necrosis.
15
Q
What are the major cells that regulate the intensity of acute inflammation?
A
Macrophages
Neutrophils
Mast Cells
15
Q
What are the major cells that regulate the intensity of acute inflammation?
A
Macrophages
Neutrophils
Mast Cells
16
Q
What are the 4 neutrophil chemotactic factors?
A
C5a
IL-8
Leukotriene B4 (LTB4)
Bacterial Products
17
Q
Where does extravasation occur?
A
Post-capillary venules
18
Q
What are the 4 steps of Extravasation?
A
- Margination & rolling
- Tight binding
- Diapedesis (transmigration)
- Migration
19
Q
In Margination & Rolling: Histamines induce P-selectin of what cells?
A
Endothelial cells (Weibel-Palade bodies)
20
Q
In Margination & Rolling: E-selectin of endothelial cells is induced by what?
A
TNFa and IL-1 (macs)
21
Q
In Margination & Rolling: Selectins bind where?
A
Selectins bind to Sialyl-Lewis X (SLex) on Leukocytes.
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
- PMNs
- C5a and LTB4
- Endothelial Cells
23
Tissue Macrophages associated with Skin:
Langerhans cells
24
Tissue Macrophages associated with Liver:
Kupffer Cells
25
Tissue Macrophages associated with Bone:
Osteoclast
26
Tissue Macrophages associated with Brain-CNS:
Microglial
27
Staphylococcal Scalded Skin Syndrome (SSSS, Ritter's Disease) is treated with what?
* Pain Management
* Bacterimia rare.
* **Nafcillin**
28
Staphylococcal Scalded Skin Syndrome (SSSS, Ritter's Disease):
Major symptom/sign
* Perioral erythema covers entire body within-**2 days of positive.**
* **Nikolsky's sign** - large blister with clear fluid, no organism, no leucocytes.
29
Staphylococcal Scalded Skin Syndrome (SSSS, Ritter's Disease):
Exfoliative toxins A or B are? allowing them to do what?
* **Serine Proteases**
* Cleave **Desmosomal cadherins** in the **stratum granulosum** layer.
* Desmosomes are cell-cell junctions.
30
Describe Pemphigus Vaguaris?
* Autoimmune destruction of desmosomes between keratinocytes.
* IgG antibody destruction of desmoglein.
* Skin and mucosal bullae
* Tombstone appearance.
31
Skin abscesses, furuncles, and carbuncles are all related to what?
Hair Follicle
32
Skin abscesses, furuncles, and carbuncles: Common complication
**Liqueficative necrosis - typical of bacteria infections, due to the hydrolytic enzymes carried out by neutrophils.**
33
Skin abscesses, furuncles, and carbuncles: Main bacterial cause?
S. Aureus occurs in 50% of cases
34
Skin abscesses, furuncles, and carbuncles: How to treat minor and major?
Minor: Warm compress to aid drainage
Major: Incision and drainage.
35
What are the six types of necrosis?
1. Coagulative
2. Liquefactive
3. Caseous
4. Fat
5. Fibrinoid
6. Gangrenous
36
Where is Coagulative necrosis not observed?
* Infarcts/ischemia in most tissues except for brain, **kidney, heart,** and **adrenal glands.**
37
Unique feature of coagulative necrosis?
Denature enzymes, **no proteolysis**.
38
Describe Liquefactive necrosis: Common occurrence, mechanism, and severe negative outcome.
* Bacterial **abscesses/brain infarcts**
* Neutrophils release **lysosomal enzymes**
* Continuous presence causes **Brain Cavitation**.
39
Describe the three mentioned causes of Caseous Necrosis and mech.
* TB, Systemic fungi, nocardia
* Macs wall of bacteria, debris surrounded by lymphocytes and activated macrophages (granuloma).
40
Describe Fat Necrosis?
* Acute pancreatitis (Enzymatic).
* Lipase breaks down triglycerides → fatty acids binds to calcium → saponification
41
Describe Fibrinoid necrosis:
* Autoimmune **vascular reaction**
* Type 3 hypersensitivity or plasma protein **fibrin** leakage.
* Thick and pink vessel walls
42
Describe Gangrenous necrosis:
* Distal extremity and GI tract, after chronic **Ischemia**
* **Dry** ischemia (coagulative)
* **Wet:** superinfection (liquefactive superimposed on coagulative).
43
Non-Bullous impetigo (pyoderma, **impetigo contagiosa**)
* **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
Bullous impetigo
* 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
What is **Ecthyma?**
* **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
Describe **Erysipelas**?
* 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
Symptoms of Cellulitis?
Redness, induration, heat, tenderness, and the distinction between infected and noninfected **area is not as clear**.
48
Cellulitis in unimmunized children is often caused by?
**H. influenzae type B.**
49
Cellulitis is 90% caused by?
GAS and S. Aureus.
50
Cellulitis associated with bites or scratches from cats and dogs?
**P. multocida**
51
Cellulitis development?
Rapid (24 to 48 hours) from minor injury to severe septicemia.
52
P. aeruginosa infection of Burn wounds? Mechanism?
* Vascular damage, tissue necrosis, and bacteremia prevent neutrophils from being able to penetrate into the wounded area resulting in severe infection.
53
Describe **Infectious folliculitis?**
* “Hot tub”
* Caused by **P. aeruginosa**
* resolves in 7 to 10 days
54
Describe **Type 1 Necrotizing Fasciitis**?
* **Mixed** microbial infection caused by both aerobic and anaerobic bacteria.
* Common after surgical procedures in patients with **diabetes and peripheral vascular disease.**
55
Describe **Type 2 Necrotizing fasciitis**?
A **mono-**microbial infection caused by group A steptococcus (GAS, S. pyogenes) and MRSA.
56
Necrotizing fasciitis caused by halophilic V. vulnificus?
Rapid progressive wound infections after exposure to contaminated sea water.
50% mortality.
57
Necrotizing infections of muscle:
* 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
Cutaneous Anthrax
* 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
Cutibacterium (Propionibacterium) acnes
* 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
Treatment of Cutibacterium acnes?
Benzoyl peroxide (antimicrobial) and Vitamin A derivatives which **reduces keratin production**
61
Describe **Cat scratch disease?**
* B. henselae
* Papule at infection site.
* **Noncaseating granuloma** with pus (**B. henselae** with **neutrophils**).
62
Describe Trench Fever:
* B. quintana:
* Homeless and HIV positive
* Relapsing fever, severe headache and leg pain.
63
4 Common disease caused by **Bartonella**
1. Cat scratch disease
2. Trench fever
3. Septicemia
4. Endocarditis: (occurs in 20%).
64
Describe **Bacillary Angiomatosis**
* 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
Treatment of Bacillary angiomatosis?
Erythromycin, doxycycline, or tetracycline.
66
Toxic shock syndrome: (TSS)
* 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 su**per-antigen**.
67
Describe **Meningococcemia?**
* **Petechial macules on the lower extremity**
* Can be Rocky Mountain spotted fever or West nile virus.
68
Describe **Disseminated gonococcal infection**?
Tender, hemorrhagic, and necrotic pustules on the fingers and palms.
69
Describe Ecthyma gangrenosa?
* Ulcerative form of impetigo
* Caused by P. aeruginosa bacteremia.
* Occurs in **neutropenic** patients.
