Skin, Wound, Bone and Joint Infections
Factors Affecting Skin Microbiome
Host physiology: sex, age, site
Environment: climate, geographical location
Immune system: previous exposures, inflammation
Host genotype: susceptibility genes (filaggrin)
Lifestyle: occupation, hygiene
Pathobiology: underlying condition (Diabetes)
Bacterial Skin Infections: Impetigo
Infection on surface layer of skin, crusting skin lesion
Common in children, very contagious
Group A streptococci, Staphylococcus aureus
Treat with oral antibiotics
Folliculitis
Infection of hair follicles, inflamed pimples
Staph aureus: area of friction & sweat gland (axilla, buttocks)
Pseudomonas aeruginosa (hot tub folliculitis)
Mild cases resolve on their own, topical antibiotics may be required
Osteomyelitis
Furuncle
Boil, deep inflammatory nodule that develops from preceding folliculitis
involves the pilosebaceous unit
Staph aureus
self resolve, warm compresses can help. Larger boils may require incision & drainage
Carbuncle
larger lesion made up of multiple furuncles.
Nape of neck
Risk Factors: eczema, obesity, diabetes
Staph aureus
May require drainage +/- oral antibiotics
Dermatophyte Infections
Transmission: person to person, from animals, from soil
Slow growing infection
Often self-resolve, topical anti-fungal if needed
Candida
Normal flora: GOT, female genital tract, skin
Overgrowth in moist warm areas
Red rash, satellite lesions. Discrete white patches
Topical antifungal treatment, may require oral antifungals
Cellulitis
Acute infection of the skin that extends into subcut tissues
Bacteria enters through broken skin any area of body
Staph. aureus, Group A streptococcus
Risk Factors: cuts, lacerations or burns.
Dry broken skin, leg/foot ulcers, unhealthy nails, diabetes, lower limb oedema/swelling
Clinical Features: spreading hot & tender erythema with oedema
Mild Infection: Oral Antibiotics, no precipitating event (Flucloxacillin)
Severe Infection: IV antibiotics, IV Flucloxacillin, IV Vancomycin
Necrotising Fasciitis
severe acute infection of fascial layers with necrosis
Can affect any part, most common in lower limbs & abdominal wall
Fournier's gangrene= necrotising fasciitis of male genitals
Often polymicrobial
Risk Factors: Trauma, surgery, diabetes, immunosuppression
Clinical Features: severe cellulitis, skin discolouration
Management: debridement, IV antibiotics
Wound/ Surgical Site Infections
Superficial incisional: skin & subcut tissue
Deep incisional: muscle & fascia
Organ space: organs & deeper space
Pt. Risk Factors: age, obesity, diabetes, smoking, immunosuppression
Surgical Factor: emergency surgery, contamination, poor blood supply, swelling, tight sutures
Septic Arthritis
Infection of joint space, haematogenous spread of bacteria or local spread
Staph aureus, Strep. A, B, C, G
Clinical features: fever, pain, swelling
Joint aspiration, blood cultures, X-ray
Antibiotics 3-4 weeks. Drainage of pus/ surgical wash out
Prosthetic Joint Infection
local spread of bacteria/ haematogenous seeding= infected implanted joint
IV Antibiotics
Coagulase - Staph (CoNS)
infection of bone, haematogenous spread/ contiguous spread
Staph. aureus, strep
Clinical features: pain, tenderness, swelling
Antimicrobial therapy 4-6 weeks. Surgery