IC14 SSTI Flashcards
What are the sites of infection and their infections?
Site of infection: Infection:
Epidermis Impetigo
Dermis Ecthyma, erysipelas
Hair Follicle Furuncles, carbuncles, skin abscess
Subcutaneous Fats Cellulitis
Fascia Necrotizing fasciitis
Muscles Myositis
What are the Physiology / Natural Host defenses?
- Desquamation to remove dead cells and microbes
- Antimicrobial sebaceous secretions / skin has pH of 4-5 so that microbes will not overgrow on the skin
- Normal skin flora ensures pathogenic organisms can’t colonize and overgrow
What is the Pathophysiology of SSTI?
Destroyed skin barrier, allows bacteria and microbes to overgrow and enter, invade and infect, SSTI + travel into deeper tissues
What are the risk factors of SSTI?
- Disruption of skin barrier
a. Trauma: laceration, surgery, wounds, animal bites, burns
b. Non-trauma: ulcers, tinea pedis, dermatitis, toe web intertrigo, chemical irritants
c. Impaired venous and lymphatic drainage –> obesity, saphenous venectomy, chronic venous insufficiency
d. Peripheral artery disease - Conditions that predispose to infection
a. Diabetic (neuropathy), cirrhosis, neutropenia, immunocompromised, HIV - History of cellulitis
What are the signs and symptoms of each SSTIs?
Impetigo:
- Epidermis (surface infection)
- Erythematous Papules –> become vesicles and pustules that can burst and form ulcers with honey-coloured crusts
- Face and extremities
Ecthyma:
- Dermis
- Ulcerated form of impetigo
- Pruritis, scratching may further spread the infection
- Face and extremities
Furuncles/boils:
- Hair follicles, can extend into subcutaneous tissue
- Purulent material
- Small abscess forms
Carbuncles:
- Hair follicles, can extend into subcutaneous tissue
- Coalesced furuncles
Skin abscess:
- Dermis, can be in deeper tissues
- Space filled with pus
- Painful, tender, swollen and erythematous nodules
Cellulitis:
- Subcutaneous fats
- Rapid onset
- Erythematous, non-raised, non-demarcated lesions (because at deep tissue)
- Fever
- Usually lower extremities, unilateral
Erysipelas:
- Dermis
- Erythematous, raised, demarcated lesion
- Face and lower extremities
Complications of cellulitis and erysipelas:
- Bacteremia, endocarditis, toxic shock, glomerulonephritis, lymphedema, osteomyelitis, necrotizing soft tissue infections
Necrotizing fasciitis:
- Fascia
- Black and erythematous
Who does not need objective evidence collected from them?
Mild SSTIs (no systemic signs of infection)
What are the objective evidence of SSTIs? When do you collect them?
NOT needed in mild SSTIs
NEED for pus, exudates, abscess
NEED for moderate to severe
NEED for those with systemic signs of infection
- Get wound sample for culture
- After cleaning wound
- From deep inside the wound
- Base of closed abscess (use needle to poke in)
- By curettage rather than swab or irrigation
- Before starting antibiotics
- Blood cultures (only for severe SSTIs with marked systemic signs of infection OR immunocompromised pts)
- Complete blood count
- Lactate
- Creatinine phosphokinase
- CRP
- Radiography, CT scan, MRI, ultrasonography
Signs of systemic illness:
SIRS criteria: 1) temp > 38 or < 36 2) HR > 90bpm 3) RR > 24bpm 4) WBC > 12x10^9 cells/L or < 4x10^9 cells/L
What are the pathogens present in impetigo and ecthyma?
Staphylococcus + Streptococcus, mainly Group A streptococcus
What antibiotics to use for impetigo and ecthyma? (choice, dose, ROA, duration)
For mild impetigo:
1. Topical Mupirocin BD (5 days)
For EMPIRIC impetigo, ecthyma:
1. PO Cephalexin (7 days)
2. PO Cloxacillin (7 days)
3. PO Clindamycin (7 days) (if penicillin allergy)
CULTURE-DIRECTED:
If Strep Group A, B specific:
- PO Pen V, amoxicillin (7 days)
If MSSA specific:
- PO cloxacillin, cephalexin (7 days)
All 7 days (except for mupirocin: 5 days)
What are the pathogens present in Purulent SSTIs e.g.
Furuncles, Carbuncles, Skin Abscess?
Mainly staphylococcus Aureus, some group A streptococcus, gram negatives, anaerobes
+/- MRSA
What are the antibiotics used in Purulent SSTIs e.g.
Furuncles, Carbuncles, Skin Abscess?
Mainly staphylococcus Aureus, some group A streptococcus, gram negatives, anaerobes
+/- MRSA
Mild:
1. Incision and drainage or warm compress
Moderate (WITH systemic signs and symptoms):
1. Incision and drainage
+ adjunctive PO antibiotics:
2. PO Cephalexin (5-10 days, usually 7 days)
3. PO Cloxacillin (5-10 days, usually 7 days)
4. PO Clindamycin (5-10 days, usually 7 days)
Severe:
1. Incision and drainage
+ adjunctive IV antibiotics:
2. IV cloxacillin (5-10 days, usually 7 days)
3. IV cefazolin (5-10 days, usually 7 days))
4. IV Clindamycin (5-10 days, usually 7 days)
5. IV vancomycin (5-10 days, usually 7 days)
EMPIRIC CA-MRSA (in USA):
1. PO Co-trimoxazole, doxycycline, clindamycin
(7 days)
EMPIRIC HA-MRSA:
1. IV Vancomycin, daptomycin, linezolid
EMPIRIC Gram negatives, anaerobes (when have skin abscess at perioral, perirectal, vulvovaginal area):
1. PO Amoxicillin-clavulanate (augmentin)
Duration: 5-10days, usually 7 days
Only give adjunctive antibiotics when:
1. Unable to drain fully
2. Lack of response to I&D
3. Extensive disease involving several sites
4. Immunocompromised
5. Extreme age
6. Signs and symptoms of systemic illness (inflammation)
CA-MRSA risk factors:
Close contact, overcrowded facilities, lack sanitation
HA-MRSA risk factors:
Infection in last 1 year, hospitalization in the last 1 year, hemodialysis
What are the pathogens present in Non-purulent SSTIs e.g. Cellulitis, Erysipelas?
Group A Streptococcus, less commonly S. Aureus,
Aeromonas, Vibrio vulnificus, pseudomonas if water exposure
What antibiotics to use for Non-purulent SSTIs e.g.
Cellulitis, Erysipelas?
Mild (without signs of systemic infection, mainly cover Strep pyogenes):
- PO penicillin V (5-10 days)
- PO cephalexin (5-10 days)
- PO cloxacillin (5-10 days)
- PO clindamycin (5-10 days) (if penicillin allergy)
Moderate (WITH systemic signs of infection, some purulence, include MSSA):
- IV cefazolin (5-10 days)
- IV cloxacillin (5-10 days)
- PO/IV Clindamycin (5-10 days) (if penicillin allergy)
Severe (with systemic signs of infection, failed oral therapy, immunocompromised –> broad coverage):
- IV pip-tazo (5-10 days)
- IV cefepime (5-10 days)
- IV meropenem (5-10 days)
If MRSA:
- IV vancomycin, daptomycin, linezolid
Duration: 5-10 days, 14 days for immunocompromised
What are some non-pharmacological measures used for managing Non-purulent SSTIs e.g. Cellulitis, Erysipelas?
- Ensure rest and limb elevation (drain edema, and inflammatory substances)
- Treat underlying conditions e.g. tinea pedis, skin dryness, limb edema
How to monitor SSTIs?
- Should improve within 48-72 hours
- If patient does not improve within 2-3 days, or progression of lesion, reassess the patient
- Switch to oral antibiotics when patient is better
- Deescalate according to culture and AST
- Stop antibiotics according to the stated duration and do not wait till wound is completely healed
- Do NOT repeat culture to check for clearance
- Look out for adverse drug reaction and allergies
