Bacterial Skin Infections Flashcards
What is Ritter’s disease?
Staphylococcal Scalded Skin Syndrome
What is the pathology of Staphylococcal Scalded Skin Syndrome?
Circulation of exfoliative toxins A or B cleave desmosomal cadherins in the stratum granulosum layer
What is the most common cause of skin abscesses, furuncles, and carbuncles?
S. aureus
What type of necrosis occurs in abscesses?
Liquefactive necrosis - typical of bacterial infections
What is erysipelas and what is the causitive agent?
Tender, superficial erythematous and edematous lesions that occurs primarily in the upper dermis and superficial lymphatics
Caused by group A strep (S. pyogenes)
What is bullous impetigo?
Localized staphylococcal scalded skin syndrome
What is the pathology of Bullous impetigo?
S. aureus produces exfoliative toxin A that causes the loss of cell adhesion in the superficial epidermis by targeting desmoglein 1
No direct bacterial colonization
What is impetigo and the most common causitive agents?
Papules progress to vesicles surrounded by erythema
Group A strep and S. Aureus
Common disease of children
What is cellulitis and the most common causitive agents?
Redness, induration, heat, and tenderness with no clear distinction between infected and noninfected area
Develops rapidly to septicemia
GAS and S. Aureus
What infection can cause cellulitis in unimmunized children?
H. influenzae
What agent manifests as ecthyma gangrenosa?
Pseudomonas
What is the cause of toxic shock syndrome?
Toxic shock syndrome toxin-1
Superantigen that causes hyperactivation of T cells
What is dry gangrene?
Form of coagulative necrosis that develops in ischemic tissue
Characteristic of ischemia of lower limb (diabetics)
What is wet gangrene?
Thriving bacteria in the lesion and has a poor prognosis due to sepsis resulting from the free communication between infected fluid and circulatory fluid
What is gas gangrene?
Bacterial infection that produces gas within tissues
What is necrotizing fasciitis?
Deep seated infection of the subcutaneous tissue leading to destruction of fascia and fat, but may spare skin
What is type I necrotizing fasciitis?
Mixed infection caused by aerobic and anaerobic bacteria and occurs most commonly after surgical procedures and in patients with diabetes and peripheral vascular disease
What is type II necrotizing fasciitis?
Monomicrobial infection caused by GAS
Can also be caused by MRSA
How does NF caused by V. vulnificus present?
Rapidly progressive wound infections after exposure to contaminated sea water
50% mortality
What organism causes gas gangrene and myonecrosis?
Clostridium spp.
Especially C. perfringens
What are the morphological characteristics of Bacillus anthracis?
G+, spore-forming
D glutamic acid capsule
What are the three parts of the B. anthracis exotoxin?
Edema factor
Lethal Factor
Protective antigen
What is the MoA of edema factor?
Activated by human calmodulin, increases intracellular cAMP - impaired flow of ions and water
What is the MoA of lethal factor?
Induces macrophages to produce high levels of cytokines that trigger shock
What is the MoA of protective antigen?
Promotes entry into phagocytic cells
What is the most common form of anthrax and how does it present?
Cutaneous anthrax
Painless papule at the site of inoculation that progresses to an ulcer and necrotic eschar
How is GI anthrax transmitted and present?
Spores in contaminated meat
Nausea, fever, abdominal pain, vomiting blood, diarrhea
What is woolsorter’s disease?
Inhalation anthrax
Death occurs within 3 days of initial symptoms (fever, SoB, cough, headache)
What is the critical diagnostic feature of woolsorter’s disease?
Widening of the mediastinum
What is the treatment for anthrax?
Penicillin
Ciprofloxacin
Doxycycline
All for 60 days
