Skin and Soft Tissue Infection Flashcards
What are the types of SSTI at the corresponding sites: epidermis, dermis, hair follicles, s/c fat, fascia, muscle
Epidermis: impetigo
Dermis: ecthyma, erysipelas
Hair follicles: folliculitis, furuncles, carbuncles
s/c fat: cellulitis
Fascia: necrotising fasciitis
Muscle: myositis
Normal pH of skin (and why) and how does it act as a chemical barrier?
pH 4-5 (acidic) -> due to production of free fatty acids from phospholipids
Chemical barrier: keeps bacteria and Candida low by regulating desquamation and resident bacteria
Is blood flow to the skin important?
Yes -> for immunity
What are 5 non-traumatic disruptions that increase risk of SSTI?
Ulcer, tinea pedis, dermatitis, toe web intertrigo, chemical irritants
What conditions predispose a person to SSTI?
Diabetes, cirrhosis, neutropenia, HIV, transplantation and immunosuppressive medications
Where should wound culture samples be collected from? Should a wound swab be done?
- deep in the wound after surface cleansed
- from the base of a closed abscess where bacteria grow
- by curettage
no wound swabs -> difficult to obtain representative sample
Progression of impetigo?
Begin as erythematous papules -> vesicles and pustules -> rupture -> dried discharge forms honey-coloured crusts
What is a furuncle and carbuncle?
Furuncle: boil
Carbuncle: cluster of furuncles
When is blood culture done for SSTI?
Immunocompromised patients or when patients show systemic symptoms (e.g. fever)
Difference between erysipelas and cellulitis?
Erysipelas affects upper dermis and has well-demarcated edges, raised, more common on face & lower extremities
Cellulitis affects s/c fat, poorly demarcated, non-elevated, more common on lower extremities
What does increased lactate levels suggest?
Tissue/organ underperfusion, possible tissue necrosis
In which condition does creatinine phosphokinase increase?
Myonecrosis, necrotising fasciitis
(CPK high means muscle, heart or brain injury)
What is the likely pathogen causing impetigo?
Staphylococci or streptococci
(bullous form caused by toxic-producing strains of S. aureus)
What is the likely pathogen causing ecthyma?
Group A Streptococci
What is the likely pathogen causing non-purulent skin conditions?
Beta-haemolytic streptococcus (Group A, B); usually Group A (Strep pyogenes)
What is the most likely pathogen causing purulent skin conditions?
S aureus, some beta-hemolytic streptococcus
What colour will S aureus look like on a culture plate?
Golden yellow
What type of bacteria are more common in skin abscesses involving the peri oral, perirectal or vulvovaginal area?
gram -ve, anaerobes
Treatment for impetigo with mild limited lesions? and duration
Topical mupirocin BD x 5 days
Treatment for impetigo and ecthyma (empiric)? and duration
PO cephalexin or cloxacillin
If penicillin allergy: PO clindamycin
Duration: 7 days
Treatment for impetigo and ecthyma (culture-directed) for S pyogenes and MSSA? and duration
S pyogenes: PO penicillin V, amoxicillin
MSSA: PO cephalexin, cloxacillin
Duration: 7 days
Treatment (empiric) for mild purulent infection?
Incision and drainage or warm compress
What is considered purulent skin infections?
Furuncles, carbuncles, skin accesses, purulent cellulitis
What is considered non-purulent skin infections?
Cellulitis, erysipelas
Treatment (empiric) for moderate (with systemic symptoms) purulent infection?
Incision and drainage + PO cloxacillin / cephalexin / clindamycin (if penicillin allergy)
Treatment (empiric) for severe purulent infection?
Incision and drainage + IV cloxacillin / cefazolin / clindamycin (if penicillin allergy) / vancomycin (last line)
Treatment (empiric) for MRSA purulent infection?
PO/IV co-trimoxazole, PO doxycycline, PO/IV clindamycin, IV vancomycin, IV daptomycin, IV linezolid
Duration of treatment for purulent infections?
5-10 days
Treatment (empiric) for gram -ve and anaerobe purulent infection?
PO/IV augmentin
Treatment (empiric) for mild non-purulent infection? What are you mainly covering for?
PO penicillin V, cephalexin, cloxacillin, clindamycin (if penicillin allergy)
[cover strep pyogenes]
Treatment (empiric) for moderate non-purulent infection (systemic signs of infection)? What are you mainly covering for?
IV cefazolin, clindamycin (if penicillin allergy)
[cover MSSA, strep pyogenes]
Treatment (empiric) for severe non-purulent infection (failed PO therapy, immunocompromised, systemic signs of infection)? What are you mainly covering for?
IV pip-tazo, cefepime, meropenem
if have MRSA risk factor: add IV vancomycin, daptomycin, linezolid
[broader coverage]
Duration of treatment for non-purulent infections?
5-10 days
14 days if immunocompromised
What does mupirocin cover?
Aerobic gram +ve esp S aureus
Non-pharm for non-purulent skin infections?
Rest, limb elevation (drain edema, inflammatory substances), treat underlying conditions (tinea pedis, dermatitis etc)
What 3 components make up the pathophysiology of diabetic foot infections?
Neuropathy, vasculopathy, immunopathy
What bacteria are involved in diabetic foot infections / pressure ulcers?
Polymicrobial
- Most common: S aureus, strep
- Gram -ve (esp in chronic wounds or prev treated with abx): E coli, Klebsiella, Proteus
- Anaerobes (esp in ischaemic/necrotic wounds)
Do you culture uninfected wounds?
No
What to cover for mild, moderate and severe diabetic foot infections / pressure ulcers?
Mild: Strep, S aureus
Moderate: strep, S aureus, gram -ve (+- pseudomonas), anaerobes
Severe: strep, S aureus, gram -ve (+ pseudomonas), anaerobes
What is considered mild, moderate and severe diabetic foot infections / pressure ulcers?
Mild: skin & SC tissue infection, erythema ≤2cm around ulcer, no signs of systemic infection
Moderate: deeper tissue infection (bone, joint), erythema >2cm around ulcer, no signs of systemic infection
Severe: same as moderate but have signs of systemic infection
What is used to treat mild diabetic foot infections / pressure ulcers?
PO cephalexin, cloxacillin, clindamycin (if penicillin allergy)
if have MRSA risk factor: PO co-trimoxazole, clindamycin, doxycycline, levofloxacin, moxifloxacin
What is used to treat moderate diabetic foot infections / pressure ulcers?
IV augmentin, cefuroxime/ceftriaxone + metronidazole
if have MRSA risk factor: IV vancomycin, daptomycin, linezolid
What is used to treat severe diabetic foot infections / pressure ulcers?
IV pip-tazo, cefepime + metronidazole, meropenem
if have MRSA risk factor: IV vancomycin, daptomycin, linezolid
Duration of treatment for diabetic foot infections / pressure ulcers?
No bone involved
- mild:
- moderate:
- severe:
Bone involved
- surgery (all infected bones & tissues removed):
- surgery (residual infected soft tissue):
- surgery (residual viable bone):
- No surgery or surgery (residual dead bone):
No bone involved
- mild: 1-2 weeks
- moderate & severe: 2-4 weeks
Bone involved
- surgery (all infected bones & tissues removed): 2-5 days
- surgery (residual infected soft tissue): 1-2 weeks
- surgery (residual viable bone): 3 weeks
- No surgery or surgery (residual dead bone): 6 weeks
Non-pharm for diabetic foot infections?
- wound care (debridement, relieve pressure on ulcer, dressings to promote healing)
- foot care (daily inspection)
- optimal glycemic control
Non-pharm for pressure ulcers?
- wound care (debridement, normal saline)
- relieve pressure (reposition Q2h)
MRSA risk factors for SSTI (5)
- recent hospitalisation
- MRSA coloniser
- long term care facility resident
- hemodialysis
- immunocompromised
When to use prophylactic abx for SSTI and what kind (dose, duration) to use?
For pts with 3-4 episodes/year of cellulitis
- PO penicillin 250-500mg BD for 4-52 weeks
- IM 2.4 MU benzathine penicillin Q2w
Which abx interacts with omeprazole and why?
Cefuroxime -> needs acidic env to be absorbed
Max clindamycin dose?
600mg TDS
