Skin and soft tissue infection Flashcards
What is an SSTI?
-Skin and soft tissue infection
-Bacterial infection of the dermis and subcutaneous tissues
Examples of SSTI
-Impetigo
-Ecthyma
-Cellulitis
-Erysipelas (lymphatics)
-Furuncle/ carbuncle
-Erysipeloid
-Ascending lymphangitis
-Necrotising fasciitis
-Gas gangrene
-Fournier’s gangrene
-Toxic shock syndrome
SSTI Disease Burden
-Common
-Incidence wide ranging up to 24.6/1000 person years
Clinical spectrum of SSTI
- Common generally mild infections which are relatively easy to treat as outpatient- I&D alone +/- oral antimicrobials
-Moderate infections (OPAT- IV)
-Severe infection (cSSTI) associated with systemic toxicity (SIRS), severe local pain, bullae formation, haemorrhagic appearance, gas, rapid spreading margins
What is involved in a severity assessment?
-History
-Vital signs (systemic involvement), extent of local involvement
-qSOFA, SIRS
What investigations are required for moderate to severe SSTI?
-Routine haem, biochem, inflammatory markers, lactate, CK, glucose
-Plain film X-ray= gas, foreign body
-Surgical review early if indicated
What is involved in diagnostic microbiology?
-I&D abscess; swab of discharging material
-Blood cultures= systemic features/ pre IV antibiotics
Sepsis 6
- Deliver high-flow oxygen
- Blood cultures prior to admin of antibiotics
- Administer empiric intravenous antibiotics
- Measure serum lactate and FBC
- Start IV resuscitation
- Commence accurate urine output measurement
Describe the microbial spectrum
-85% Group A Streptococcus (S pyogenes) (B.C.G)
-Staphylococcus aureus (incl MRSA)
=Blood cultures positive <5%
=Needle aspiration 5-40%
=Punch biopsy 20-30%
-Myriad other pathogens in specific clinical settings/ risk hosts: require consideration/ diagnosis: aspirate/ skin biopsy
=wounds, water exposure, bites, injection drug use
Describe necrotising fasciitis and treatment of it
-Severe/ disproportionate pain, woody tissue
-Finger test
-Systemic toxicity, mortality =10% (up to 50-70%)
-Failure to respond to antimicrobial initiation
-Requires broad spectrum high dose parenteral therapy
-Clindamycin adjunctive anti-toxin effect and modulation of cytokines
-Surgical debridement often required and should not be delayed- therapeutic and diagnostic
-Potential role for IVIG (immunoglobulin) in STSS
Most appropriate initial antibiotics for necrotising fasciitis
-Amoxicillin
-Piperacillin/ Tazobactam
-Ciprofloxacin
-Phenoxymethylpenicillin (Pen V)
-Flucloxacillin IV (!)
Antibiotics and considerations for Impetigo
-Flucloxacillin 0.5-1.0g qds po
-Clarithromycin 500mg bd po
Considerations:
-limited: top mupirocin
-Clindamycin po an alternative
Antibiotics and considerations for Erysipelas (Strep)
-Amoxicillin/ Flucloxacillin/ Clarithromycin/ Cephalexin po
Considerations: benzylpenicillin 2.4g 4-6hrly IV
Antibiotics and considerations for MSSA Cellulitis
-Mild: oral flucloxacillin/ clarithromycin
-Severe: flucloxacillin
Considerations: Doxycycline, co-trimoxazole, clindamycin alternatives
Antibiotics and considerations of MRSA
-Vancomycin
Considerations: oral alternatives (doxycycline, co-trimoxazole, clindamycin)
Antibiotics and considerations of Necrotising fasciitis
-Flucloxacillin/ benzylpenicillin/ clindamycin/ gentamycin/ metronidazole
Considerations: polymicrobial infection requires empiric broad spectrum coverage IV
Length of antibiotic duration for SSTI
-Mild 7 days
-Mod/Severe 10-14 days, definite clinical improvement
Sites of SSTI involvement
-Lower limb most common
-Face
=Preseptal cellulitis
=Peri-orbital cellulitis: deeper involving tissues of orbit (CT scan)
-Hands
-Soft tissue overlying joints
Host predispositions to SSTI
-DM
-Peripheral vascular disease
-Lymphoedema
-Obesity
-Prior episodes
-Skin disease (eczema, psoriasis)
-Immunocompromised (fungal, atypical mycobacteria)
-Malignancy
-Chronic liver disease
-Tinea pedis/ onychomycosis
Risk factors for recurrent SSTI/ cellulitis
-DM
-Obesity
-Fungal infection
-Lymphoedema
Streptococcal species recurrent SSTI/ cellulitis
-Rapid onset at previous site
-1/3 recur
-Prevent: skin care, weight loss, manage oedema
-Prophylaxis: 3 episodes/ year- Pen V/ Macrolide
Staph aureus recurrent SSTI/ cellulitis
-Different sites
-Purulent skin infections: I&D
-Decolonise
What does recurrent SSTI mimic?
-Skin disease= varicose eczema, drug eruption, dressing reaction, GvHD
-Zoster
-Erythema multiforme
-Erythema nodosum
-Gout
-DVT
-Ruptured bakers cyst
Describe clostridium spp infection
-Exposure: wound contam IDU (spores)
-Clinical syndrome: gas gangrene, myonecrosis
-Considerations: massive tissue oedema, V high WCC
Describe pseudomonas aeruginosa infection
-Exposure: water, hot tub
-Clinical syndrome: Whirlpool folliculitis, ecthyma, gangrenosum
-Considerations: immunocompromised
Describe vibrio vulnificus infection
-Exposure: saltwater, fish handling
-Clinical syndrome: gas gangrene, myonecrosis
-Considerations: liver disease, Fe overload, malignancy
Describe Pasteurella spp infection
-Exposure: dog/ cat bite/ wound
-Clinical syndrome: cSSTI
-Considerations: Short incubation
Describe anthrax infection
-Exposure: IDA, textile workers
-Clinical syndrome: massive oedema/ tissue necrosis/ local oedema/ eschar
-Considerations: debridement
