Skin, Soft Tissue, Bone and Joint Infections Flashcards
What do the clinical manifestations of skin and soft tissue infections include?
Erythema Warmth Tenderness Systemic symptoms - Chills - Fever
What is the differential diagnosis for unilateral leg erythema, swelling, and tenderness, of rapid onset?
DVT Cellulitis Localised infection Eczema/contact dermatitis Compartment syndrome Necrotising fasciitis
What is the relevance of cracked heels and tinea between the toes in skin and soft tissue infections?
Candida and cracked skin allow entry of bacteria into dermal layer
What is cellulitis?
Acute inflammatory process involving skin and soft tissues
What are the features of cellulitis?
Spreading, erythematous rash
Most cases involve lower limbs
Almost always unilateral - if not, limbs have different pattern
Chills and fevers may precede localising symptoms and signs
Red, warm, tender rash
Often associated with lymphangitis
What can happen in severe or protracted cellulitis?
Abscess - rare
Bullae
Vesicles
What are the risk factors for cellulitis?
Lymphatic stasis Peripheral oedema - with skin breaches Trauma IV drug use Ulcers Wounds Dermatophytic infections
What pathogens usually cause cellulitis?
Group A Streptococcus - Potential to rapidly go to necrotising fasciitis - Most likely cause Other Strep Staph aureus Coagulase -ve Staph
How is cellulitis diagnosed?
Usually clinical - epidemiology and history important clues to underlying microbiology Swab pus, if present Blood cultures indicated for - Fever - Extensive cellulitis - Immunosuppression - Lack of response to empiric therapy - Suspicion of unusual pathogen
When is imaging helpful in the diagnosis of cellulitis?
Ultrasound to differentiate DVT
MRI/CT if suspicion of necrotising fasciitis/pyomyositis
Which pathogens are likely to cause skin infections in IV drug users?
Typical cellulitis pathogens
Oral flora
Which pathogens are likely to cause skin infections post burns?
Typical pathogens
Pseudomonas aeruginosa
Enterobacteriaeciae
Acinetobacter spp
Which pathogens are likely to cause skin infections in immunocompromised hosts?
Typical pathogens Gram -ve bacteria Fungi Viruses Mycobacteria
Which pathogens are likely to cause skin infections in seawater exposure?
Vibrio spp
Which pathogens are likely to cause skin infections in freshwater or mud exposure?
Aeromonas spp
Mycobacterium marinum
Which pathogens are likely to cause skin infections due to dog or cat bites?
Typical pathogens
Oral Streptococci
Oral anaerobes
Which pathogens are likely to cause skin infections due to human bites?
Typical pathogens
Oral flora
What is the management of cellulitis?
Oral preparations Di/flucloxacillin - Good for Staph and Strep - Doesn't cover MRSA, Gram -ves, anaerobes Penicillin - Staph pyogenes cultured/suspected Cephalexin - For hypersensitivity to penicillins
For whom should IV antibiotics in the treatment of cellulitis be reserved?
High fever
Systemic toxicity
Facial cellulitis
How long does cellulitis take to resolve?
7-10 days to start
2 weeks to fully
Therefore don’t need to treat with antibiotics until redness gone
What is the adjunctive and preventative management for cellulitis?
Management of lower limb ulcers and oedema/venous insufficiency - Dressings - Compression stockings - Leg elevation - Diuretics Keep skin hydrated = emollients Assess for and manage tinea pedis
What is chronic lymphoedema?
When lymphatic load exceeds transport capacity of lymphatic system
What are the risk factors for chronic lymphoedema?
Trauma, especially recurrent Malignancy, and its treatment - Keep in people who've had all lymph nodes removed in arm Chronic venous insufficiency Obesity Inflammatory disorders
What are the features of chronic lymphoedema?
Tight, swollen legs > discomfort
Chronic condition compared to cellulitis
May become super-infected
What is the management for chronic lymphoedema?
Exercise - gentle resistance training
Compression bandaging
Massage
Meticulous skin and nail care
Which conditions can be misdiagnosed as cellulitis?
Acute contact dermatitis Septic bursitis Septic arthritis DVT Gout Thrombophlebitis Lipdermatosclerosis/venous insufficiency/varicose eczema
What are the features of acute contact dermatitis?
Dry/erythematous/eczematous skin
Exposure to irritant/caustic chemical
What is the treatment for acute contact dermatitis?
Avoid causative agent
Topical steroids
Emollients
What are the features of septic bursitis?
Commonly affects prepatellar and olecranon bursae Pain Tenderness Erythema Warmth Preceding local trauma Usual pathogen = Staph aureus
What is the treatment for septic bursitis?
Treat as per cellulitis
Surgical drainage if severe
What are the features of septic arthritis?
(Usually) single swollen, painful joint Warmth Erythematous Restricted movement \+/- fevers
What is the management for septic arthritis?
Surgical washout
Deep specimens for culture and susceptibility testing
IV antibiotics
What is a differential diagnosis for septic arthritis?
Gout
- Moderately high WCC
- Urate crystals
What are the features of DVT?
Swollen, tender, erythematous limb Risk factors - Immobilisation - Recent surgery - Obesity - Previous venous thromboembolism - Trauma - Malignancy - Pregnancy - OCP use
What is the management for DVT?
Confirm diagnosis with ultrasound
Anticoagulation
What are the features of gout?
Urate crystal deposition often over MTP joint
Acute and chronic arthritis +/- tophi
What is the management of gout?
Diagnosis: urate crystals from aspirated joint/bursa
Treatment
- Acute
- NSAIDs
- Colchicine
- Glucocorticoids
- Chronic: allopurinol > decreases serum uric acid
How can you differentiate between gout and cellulitis?
Gout responds to treatment faster than cellulitis
If start cellulitis and gout treatment at same time, gout responds in 48 hours
Not certain that it’s gout, but more likely to be gout
What are the features of thrombophlebitis?
Inflammation and thrombus within vein
What is the management for thrombophlebitis?
Diagnose clinically/with ultrasound
Treatment: symptomatic +/- compression/anticoagulation
What are the features shared by lipodermatosclerosis, venous insufficiency, and varicose eczema?
Chronic Absence of fever and heat Circumferential and usually bilateral, compared to cellulitis Limb - Discomfort - Pain - Swelling May see - Oedema - Pigmentation - Venous ulcers - Varicose veins
What are differential diagnoses for a history of painful, swollen, erythematous limb, where the important clinical features are
- Haemodynamic instability
- Pain as dominant feature
Necrotising fasciitis
Pyomyositis
Streptococcal necrotising myositis
Clostridial necrotising cellulitis = gas gangrene
ALL severe, rapidly progressing, potentially fatal infections
What other features in the history, other than the presenting complaint, can help differentiate the cause of an infection involving deeper tissue planes?
Recent surgery Crushing/penetrating trauma Chronic skin ulceration Debilitating illness Immunocompromise Elderly Diabetes Lymphoedema
What is the difference between type I and type II necrotising fasciitis and gas gangrene?
Type I = polymicrobial
Type II = mono-microbial
When is type I necrotising fasciitis or gas gangrene more likely?
Post surgery Peripheral vascular disease Diabetes Decubitus ulcers = pressure sores Spontaneous mucosal tears of GI/GU tract
What are the common causative agents of type II necrotising fasciitis or gas gangrene?
Strep pyogenes Clostridium spp Vibrio vulnificus Aeromonas hydrophila MRSA
What are the features of necrotising fasciitis and gas gangrene?
Necrosis of - Skin - Subcutaneous tissue - Muscle Prompt surgical review +/- intervention needed if - Skin sloughing - Purple bullae - Marked oedema - Systemic toxicity Surgical exploration can be life-saving
What are potential markers of deep-seated infections?
Severe pain out of proportion with other clinical findings Systemic toxicity - Hypotension - Tachycardia - High fever Gas in soft tissues - Crepitus O/E - Seen on x-ray/CT Clinical deterioration Progressive skin necrosis Bullae Elevated CK > muscle destruction
What is the management for deep-seated soft tissue infections?
Empirical antibiotics - Meropenem - Vancomycin - Clindamycin Surgical debridement
What are the differential diagnoses for a painful, swollen joint?
Septic arthritis Traumatic effusion Haemarthrosis Gout/pseudogout Adjacent osteomyelitis Bursitis/cellulitis
What are the risk factors for septic arthritis?
Local trauma Age >80 Rheumatoid arthritis Prosthetic joint Recent joint surgery Skin infection IV drug use Prior intra-articular steroid injection
What is the pathogenesis of septic arthritis?
Mostly blood-borne
Direct inoculation less common
Bacteria invade cartilage > cause micro-absecesses > cartilage destruction if no prompt, appropriate treatment
What are the investigations required for septic arthritis?
Prompt joint aspiration
- >50 000 WCC
Blood cultures in acute cases
Synovial biopsy in sub-acute/chronic disease
WCC, ESR, and CRP likely to be elevated
CT/MRI may be helpful in assessing degree of joint damage
What is the treatment for septic arthritis?
Joint washout for acute, purulent arthritis
Empiric antibiotics to cover Gram +ve pathogens
- Flucloxacillin/cephazolin
Don’t delay starting treatment
Minimum 6 weeks of antibiotics
- Minimum 2 weeks IV initially
- 4 weeks oral
Is osteomyelitis always acute?
No, can be either acute or chronic
What is the pathogenesis of osteomyelitis?
Contiguous spread from adjacent - Skin - Soft tissue - Joint Haematogenous seeding - Common in children
What is the treatment for osteomyelitis?
Prolonged antibiotics
Make every effort to ID putative organism before starting therapy
- Difficult to get microbiological sample
What are the features of osteomyelitis associated with prosthetic devices?
Coagulase -ve Staph become more important
Foreign body removal needed to achieve cure
Complicated management
What are the features of osteomyelitis associated with trauma, bites, and penetrating wounds?
Infections from bites and punch wounds commonly polymicrobial
Appropriate debridement
Consider infected fracture site when osteomyelitis secondary to trauma
What are the features of osteomyelitis associated with neuropathy and/or vascular isufficiency?
Common complication in deep foot ulcers, especially in vascular insufficiency and/or diabetic peripheral neuropathy
Commonly polymicrobial
Osteomyelitis confirmed if surgical probe ID’s bone at ulcer base
What are the features of osteomyelitis associated with skull base osteomyelitis?
Often associated with ear disease
Risk factors
- Chronic otitis
- Diabetes
What is the management of osteomyelitis?
Immobilisation Analgesia IV antibiotics directed towards pathogen Prolonged course - Relapse rates high if patients under-treated
