L8 Infections in Skin, Joints and Bones Flashcards
What does SSSI stand for?
Skin-skin structure infections
Main organism causing infections
Staphylococcus aureus
Streptococcus pyogenes
S. aureus characteristics
Gram-positive coccus (clusters)
Catalase positive
33 different virulence factors
S. pyogenes characteristics
Gram-positive coccus (chains)
Catalase negative
Lancefield group A strep
Skin inhospitable environemnt
- Dry
- Constant shedding
- Low pH
- Sebaceous secretion
- Competitive with resident microbiota
Types of skin infections resulting from trauma
Accidental e.g. scrapes and cuts
Deliberate e.g. survey
What can skin infections result from?
Haematogenous colonisation
Folliculitis
Superficial infection of hair follicle
S. aureus
Hot tub folliculitis = pseudomonas aeruginosa
Furuncle
Deep version of folliculitis
Still involves a single follicle
Carbuncle
Collection of furuncles
Extend into subcutaneous fat
Drain fluid prior to antibiotic treatment
Impetigo
Superficial skin infection
Highly infectious
Group A streptococci s. aureus
Disrupts corneal layer of skin
SSSS (Staphylococci scalded skin syndrome)
S. aureus Exfoliative exotoxin Children under 6 mainly Risk of secondary skin infection Increased mortality in adults
Erysipelas
Superficial form of cellulitis
Distinct areas between inflamed and non-inflamed areas
Group A streptococci
Cellulitis
Unable to distinguish as much between inflamed and non-inflamed areas
Group A streptococci
Lead to sepsis and septic shock
Surgical wound infection
S. aureus = antibiotic prophylaxis frequently employed
Necrotising fascilitis
Uncommon and severe Superficial and deep (affect any body site) Start with group A strep - Cellulitis - Impaired blood flow (necrosis) - Anaerobe involvement - Rapid tissue destruction
Gangrene
Deep tissue infection
Clostridium spp.
Arises in areas of poor blood flow
Gas gangrene = C. perfingens
Anthrax
Bacillus anthracis
Gram positive sporing bacillus
Found in animals etc
Cutaneous Anthrax = skin lesions (black ‘eschar’
Rickettsial infection
Rickettsia spp. (obligate intracellular)
Transmitted by fleas etc
Cat and dog bites
Pasturella multocida infection
Capnocytophaga canimorus
Rat bites
Spirillum minus
Streptobacillus moniliformis
Human bites
Oral commensal microbiota
Eikenella corrodens
Lyme disease
Borellia burgdorferi
Transmitted to humans by lxodes tick
Lead to fever, muscle pain, headache
Osteomyelitis
Infection of bone
Pain and swelling around affected area
Arthritis
Swollen and painful joints
Caused by immunological reaction (reactive rheumatoid) or infection (septic arthritis)
