Severe Skin and Soft Tissue Infections Flashcards
Describe the features of diabetes mellitus that predispose to diabetic foot
infections
Diabetes can progress to peripheral neuropathy and compromised sensation. Reduced sensation and reduced sweating in toes leads to dry and cracked feet, providing entry routes for bacteria.
This eventually progresses to vascular disease (compromised blood supply), either microvascular or peripheral vascular.
Charcot’s foot also contributes: reduced sensation in the feet from diabetes mellitus, which leads to pressure and rubbing on the foot that would normally be avoided. This leads to an ulcer
Which bacterial species often causes the dead tissue in foot infections?
Anaerobes
Describe necrotizing fasciitis and name the common organisms causing it
A deep, rapidly spreading infection
Type 1 is polymicrobial and the most common especially in diabetics, elderly and alcoholics
Type 2 is monomicrobial and often follows minor trauma.
Bacteria likely seed the area via the blood stream.
Common bacteria: Group A strep and S.aureus
What are the gram positive bacteria in DFIs?
Staph aureus
Strep species
What are the gram negative bacteria in DFIs?
Enterobacteriaceae
Pseudomonas aeruginosa
What are the anaerobes in DFIs?
Clostridium
Bacterioides
How do you manage a clinically non-infected diabetic foot ulcer?
Debridement and dressings
Monitor closely
Describe the three stage assessment of an infected foot ulcer in a diabetic
- Determine extent and severity
- Identify underlying factors that can predispose to and promote infection
- Assess the microbial aetology
How do you manage a clinically infected diabetic foot ulcer?
Mild, acute wound infections can usually be managed by GPs, using oral antibiotics
Deep and chronic infections/infections with systemic toxicity, require immediate referral to hospital.
Treatment will then include: surgical debridement
broad spectrum antibiotics via HITH (tazocin/ertapenem)
Off-loading using aircast boots, plaster casts etc
-Glycaemic control for better wound healing
What are the four types of assessment for a DFU?
Clinical assessment - history/examination
Lab assessment - inflammatory markers and C-reactive proteins
Radiological assessment - X-ray. nuclear scan and MRI
Microbial assessment
Describe the pathogenesis of necrotizing faciitis
Bacteria are in the deep tissue so there is little to see early on
Swelling, inflammation and thrombosis starts, and leads to ischaemia and necrosis
Pus tracks along fascial planes
Infection then spreads into the lymphatics and the blood stream
This leads to swollen discoloured skin, blistering, dusky skin and the cutaneous gangrene - wood-hard tissues
20-40% mortality with treatment
What would cause you to suspect necrotizing fasciitis?
Pain, systemic illness, neutrophilia, high CRP, end organ involvement (abnormal renal/liver function tests)
How can you diagnose Necrotising fasciitis?
Blood culture, skin swabs, blister fluid and computerised tomography
How do you treat necrotizing fasciitis?
Repeated, aggressive surgeries to debride the area
Antibiotics - IV meropenem for g pos/neg and anaerobes, vancomycin for MRSA and clindamycin for g pos and turning off toxin production
You can target IV therapy to GAS with penicillin + clindamycin
What is Clostridial myonecrosis?
It is ‘gas gangrene’ that follows penetrating injuries. It can occur in necrotising fasciitis.
More common when soil/faeces gets into a wound
