56 Bone and joint infections Flashcards
What are the three types of bone infection pathogenesis?
Haematogenous.
Contiguous focus (spread from adjacent area).
Direct inoculation.
What are the four classifications of osteomyelitis?
I. Medullary (haematogenous).
II. Superficial (contiguous).
III. Localised: full thickness, stable.
IV. Diffuse: unstable bone.
How does osteomyelitis present? (2 + 4).
Pain.
Reduced movement of affected limb.
(Soft tissue swelling, erythema, warmth, tenderness).
Which organisms cause osteomyelitis? (7).
Staphylococcus aureus (60%) Streptococci. Enterococci. Gram -ve bacilli. Anaerobes. Mycobacterium tuberculosis, Brucella (indolent spinal).
Who gets gram -ve bacilli osteomyelitis? (3).
Organisms? (3).
Premature babies, IVDU’s, sickle cell.
Salmonella, Klebsiella, Pseudomonas aeruginosa.
How is osteomyelitis diagnosed?
Gold standard: cultures + histology of bone biopsy.
Blood cultures +ve in 50%.
What is C-reactive protein used for in osteomyelitis?
Monitor therapy response.
Limited diagnostic value.
In general, how is osteomyelitis treated?
IV antimicrobials ± surgery.
Avoid empirical therapy.
Which antimicrobials achieve acceptable levels in bone? (5)
Clindamycin. Ciprofloxacin. Vancomycin. ß-lactams. Gentamicin.
What is the agent of choice for staph aureus osteomyelitis?
Flucloxacillin.
Define septic arthritis:
Inflammatory reaction in a joint space caused by infection.
What is the pathogenesis of a native joint infection?
Entrance via blood or trauma.
Synovial tissue is highly vascular and lacks basement membrane -> seeding.
What are the predisposing factors to a native joint infection? (4).
Immunosuppressive disease.
Intravenous drug use.
Trauma.
Rheumatoid arthritis.
What is the pathogenesis of a prosthetic joint infection? (3).
Prosthesis/cement provides base for infection.
Phagocytosis difficulty due to biofilm. Macrophages secreting enzymes causes joint instability.
What are the predisposing factors to a prosthetic joint infection? (7).
Prior surgery. RA. Corticosteroid therapy. Diabetes mellitus. Poor nutrition. Obesity. Advanced age.
How does septic arthritis present? (4 + 3).
Joint: pain, swelling, tenderness, redness, limited movement.
Fever, chills, night sweats.
Which viruses can cause septic arthritis (3) and when?
Parvovirus B19, Rubella, Mumps.
As part of systemic illness.
Which organisms cause septic arthritis? (5).
Staph aureus. Streptococci. Gram -ve bacilli. Anaerobes: peptostreptococci, peptococci. Mycobacteria.
Which organisms specifically cause native septic arthritis? (3).
Haemophilus influenzae.
Neisseria gonorrhoea.
Neisseria meningitidis.
Which organisms specifically cause prosthetic joint infection? (through contamination from skin) (5)
Coagulase negative staphylococci. Enterococci. Corynebacteria. Propionibacteria. Bacillus spp.
Which test is used to exclude gout as a differential with septic joint infection?
Crystal examination.
How is septic arthritis diagnosed? (4).
Joint aspirate exam: Raised WCC > 75% polymorphs. Gram stain. Culture. ? PCR.
How is native joint infection treated? (2).
Joint drainage/washout.
Empirical then directed IV antimicrobial therapy for 2-4weeks.
How is prosthetic joint infection treated?
Removal or replacement of prosthesis.
Empirical then directed IV antimicrobial therapy for 6 weeks.
Which antimicrobials are used for a prosthetic joint infection with S.aureus?
Flucloxacillin plus rifampicin.
Which antimicrobials are used for a prosthetic joint infection with coagulase negative staphylococci?
Vancomycin IV plus rifampicin.
