SSTI Flashcards
1
Q
Boundary Membrane Concept
A
- Exists on external aspects of body
- Consists of layer(s) epithelial cells bound to each other by tight junctions, overlies a basement membrane
- Provides water tight barrier
- Separates epithelium from underlying connective tissue space
- Microbial organisms live on the barrier membrane
- Kept outside of the interstitium by the barrier membrane
- No immune response is provoked
2
Q
Barrier Violation
A
- Injury to the boundary membrane allows microbial penetration into interstitium
- Bacterial virulence can be variable, from severe to minimal
- Contamination or infection
3
Q
Uncomplicated SSTIs
A
- Superficial: cellulitis, impetiginous lesions, furnucles, simple abscesses
- Treatment usually requires antibiotics and/or simple incision and drainage
4
Q
Complicated SSTI
A
- Deep soft tissue infections: extreme pain, violaceous bullae, cutaneous hemorrhage, skin sloughing, rapid progression, gas in tissue
- May require surgical intervention: infected ulcers, infected burns, and major abscesses
- Significant underlying disease which complicates the response to treatment
- May require extensive surgical debridement and reconstruction
5
Q
Microbiology of SSTIs
A
- S. aureus ~50%
- Strept. pyogenes
- Site specific infections: indigenous organisms
- Immunocompromised + Complicated SSTIs: multiple/uncommon organisms
- Polymicrobial necrotizing fasciitis: mixed infections with anaerobes and aerobes
- Monomicrobial necrotizing fasciitis: S. pyogenes
6
Q
Abscesses + Antibiotics Indications
A
- Antibiotics not necessary for most: usually just drain and wound care
- Signs of infection: fever, elevated WBCs, left shift, septic shock
- Cellulitis or phlegmon
- Immunocompromised
- Certain foreign bodies (Marlex mesh)
7
Q
Cellulitis
A
- Spreading infection affecting epidermis and dermis
- Common pathogen: GAS, S. aureus, Group B/C/G strept
8
Q
Cellulitis Presentation
A
- Swelling
- Redness
- Edema
- Pain
- Nonelevated
- Poorly defined margins
- Lymphadenopathy
- Fever/chills: rare unless chronic, underlying disease, or immunocompromised
9
Q
SSTI General Treatment Rules
A
-Antibiotic therapy: 10-14 days
10
Q
Purulent SSTI Treatment
A
- Mild Infection: purulent SSTI, incision and drainage indicated
- Moderate: patients with purulent infection with systemic signs of infection
- Severe: failed incision/drainage plus oral antibiotics or those with severe systemic signs, immunocompromised
11
Q
Severe Systemic Signs
A
- > 38 C Fever
- Tachycardia
- Tachypnea
- Abnormal WBC
12
Q
Nonpurulent SSTI Treatment
A
- Mild Infection: typical cellulitis/erysipelas with no focus of purulence
- Moderate: typical cellulitis/erysipelas with systemic signs of infection
- Severe: failed oral antibiotic/systemic signs of infection, immunocompromised, signs of deeper infection like bullae, sloughing, hypotension, or evidence of organ dysfunction
13
Q
Erysipelas
A
- Distinct type of superficial cellulitis with extensive lymphatic involvement
- Almost always GAS
- Common in infants, young kids, elderly, and patients with nephrotic syndrome
- Manifestation: lesion with sharp, elevated border, on face/scalp/hands/genitalia, fever and leukocytosis
- Treatment: Mild/moderate non-purulent SSTI
14
Q
Impetigo
A
- Superficial cellulitis by GAS (honey crust, non-bullous) and/or S. aureus (bullous, ruptured)
- Common in children during hot/humid weather
- Spread through close contact and little to no signs of systemic infection
- Small, fluid-filled vesicles that develop into puss-filled blisters that rupture and crust, pruritus
15
Q
Impetigo Treatment
A
- Depends on number of lesions, location, and need to limit spread
- Topical: mupirocin ointment to lesions TID
- Oral: numerous lesions, location prevents topical use, or not responding to topicals
- See moderate treatment for purulent SSTI
16
Q
Necrotizing Fasciitis
A
- SC infection that tracks along fascial planes and extends beyond superficial infection signs
- Extension from a lesion in 80% of cases
- Presentation: cellulitis which can advance rapidly with systemic toxicity (high fevers, lethargy, confusion), cellulitis, edema, skin discoloration or gangrene
- Usually lower extremities
17
Q
Necrotizing Fasciitis Etiology
A
- Monomicrobial: GAS, S. aureus, Clostridium spp. (mortality in 50-70% in pts. with hypotension/organ failure
- Polymicrobial: average of 5 per wound usually from surgical wounds, ulcers, or abscess
18
Q
Necrotizing Fasciitis Diagnosis
A
- Clinical judgement
- Incision and probing if no resistant to SC probing then Nec. Fasciitis
- Gram-stain and culture
19
Q
Necrotizing Fasciitis Treatment
A
-Prompt surgical debridement
Antibiotic Options
- PCN G 24 mU/day IV + Clinda 900 IV q8h (eagle effect)
- MRSA suspected: Add vanco (trough 15-20 mcg/mL)
- Polymicrobial: Vanco + Zosyn 3.375-4.5g IV q6-8h OR Imipenem 500 mg IV q6h OR Meropenem 1g IV q8h
20
Q
DFI
A
- Diabetic Foot Infections
- 15-20% of diabetics will get hospitalized for this
- Requires attention to local and systemic aspects
- Aerobic, Gram “+” are most common (S. aureus)
- Can get Gram “-“ with chronic infections and may be anaerobes if ischemia/gangrene arises
- Optimal DFI management can reduce infection related morbidity and the need/duration of hospitalization
21
Q
DFI Risk Factors
A
- Neuropathy
- Angiopathy and ischemia
- Immunologic defects
22
Q
DFI Presentation
A
- Polymicrobial in nature
- Often more extensive than they appear with paronychia, middle foot, toe web, mal perforans puncture wounds
- May be complicated by necrotizing cellulitis, osteomyelitis
23
Q
DFI Treatments
A
- Local wound care
- Immobilization
- Drainage and debridement
- Control of hyperglycemia
- Antibiotics: ORal v.s. IV for 2 weeks (6 for osteomyelitis)
- Amputation is LAST resort
24
Q
DFI Grades
A
- Grade 1-2: non-limb threatening
- Grade 3: Possibly limb threatening
- Grade 4: Limb threatening
25
Q
DFI Treatment Administration/Duration
A
- Mild: topical or oral, outpatient, 1-2 weeks and can extend to 4 weeks if slow to resolve
- Moderate: Oral, outpatient or inpatient, 1-3 weeks
- Severe: initiallyIV then switch to oral when possible, inpatient then outpatient, 2-4 weeks of treatment
26
Q
Dog Bites
A
- Localized cellulitis and pain
- 5% become infected
- Treat only if severe or co-morbidity
- Likely pathogens: Pasteurella canis, S. aureus, Bacteroides spp.
27
Q
Dog Bite Treatment
A
- Augmentin 875/125 mg BID or 500/125 TID po
- PCN Allergy: Clinda 450 mg TID OR Clinda + Bacrim in children
- *Other options for adults not listed**
- Duration: 10-14days
- Consider rabies?
28
Q
Cat Bites
A
- Localized cellulitis and pain (osteo)
- 80% become infected
- Culture and treat empirically
- Most like Pasteurella multocida or S. aureus
29
Q
Cat Bite Treatments
A
- Augmentin: 875/125 mg BID or 500/125 mg TID PO
- Cefuroxime axetil: 500 mg BID PO (NO CEPHALEXIN)
- Doxycycline 100 mg BID PO
- Duration 10-14 days
30
Q
Human Bites
A
- Localized cellulitis and pain, purulent discharge, decreased range of motion (osteo, septic arthritis, tenosynovitis
- More serious than animal bites with higher rates of infection
- Likely pathogens: Viridans strept, S. epidermidis, corynebacterium, S. aureus, eikenella, Bacteroides spp., peptostreptococcus
31
Q
Human Bite Wound Treatment
A
- General: cleaning, irrigation, debridement
- Early (not infected): Augmentin 875/125 mg BID PO x 5 days
32
Q
Human Bites: Late Treatment
A
-Signs of infection, usually within 12-24 hours
-Unasyn: 1.5-3g IV q6h
OR
-Cefoxitin 1g IV q8h
OR
-Zosyn 3.375 IV q6h or 4hr infusion 3.375g IV q8h
-PCN allergy: Clinda 600-900mg IV q8h + Cipro 400 mg IV q12h OR Bactrim 10 mg/kg/day
