Microbiology Bone and Joint infections Flashcards
Osteomyelitis Description
A progressive infectious process resulting in inflammatory destruction, bone necrosis (sequestrum) and new bone formation (involcrum). Can be acute or chronic
Osteomyelitis Pathogenesis requires
High innocula
Trauma
Or foreign material
Osteomyelitis 3 Types
Haematogenous
Contiguous
Diabetic
Osteomyelitis Haematogenous
Following bacteraemia, especially in children, metaphyseal area of long bones
Osteomyelitis Contiguous
After trauma o surgery or overlying soft tissue infection.
May be associated with prosthesis/pins/plates
Osteomyelitis Diabetic osteomyelitis
- A consequence of reduced vascularity, neuropathic skin changes, decreased local immunity and metabolic disturbance
- Often associated with foot ulcer (s)
Osteomyelitis Diabetic osteomyelitis assume and treatment
Assume osteomyelitis if bone evident at the base of ulcer
Often results in amputation
Osteomyelitis Signs and Symptoms
May be acute → pain, swelling, overlying inflammation
Infants may have few localising signs
May be evidence of tauma, surgery
Usually chronic → may be minimal signs, often a sinus, old scars, may be acute inflammation
Osteomyelitis X-ray findings
Periosteal thickening/elevation on Xray
Lysis and sclerosis
Osteomyelitis Investigations
Blood cultures, FBC, CRP Deep tissues from theatre Sinus swabs NEVER Wound swabs – may be heavily colonised Imaging
Osteomyelitis Treatment
Give antibiotics after organism found
Osteomyelitis Pathogens
Staphylococcus aureus – most common
→ has receptors ‘adhesins’ – for bone matrix, collagen-binding adhesion (cartilage) fibronectin-binding adhesins – 9foreign material)
Septic Arthritis → Description
Infection of joint space haematogenous or contiguous
Septic Arthritis →Most commonly seen in
Hip or Knee
Usually mono-articular
Septic Arthritis →Predisposition
Rheumatoid Arthritis
Joint Disease
Septic Arthritis →Pathogenesis
Synovial membrane highly vascular
Local polymorphonuclear response
→ Release of proteolytic enzymes and bacterial toxins
→ Rapid cartilage destruction, joint effusion
→ Decreases blood supply
Septic Arthritis → Complications
Decreased function of joint, if not treated promptly
Septic Arthritis → Signs and Symptoms
Painful hot swollen joint +/- malaise, pyrexia
Unable to weight bear, decrease range of movement
Septic Arthritis → Pathogens
- Staph aureus or strep
- Haemophilius influenza of <3 years – but much less common since HiB vaccine
- Neisserria gonorrhoea in young adults
- Less common → Gram-negative infection e.g. pseudomonas in IVDU
- 10% infections are polymicrobial
Reactive Arthritis → Description
- May occur following infectious diarrhoea e.g. Salmonella, Campylobacter, Yernisina and Shigella.
- Also following Chlamydia, gonorrhoea (Reiters syndrome), hepatitis B.
Reactive Arthritis → Investigations
- Bacteria are not cultured from the joint arthritis is an inflammatory reaction
- Serology or recent +ve stool cultures/GU swabs confirm diagnosis
Prosthetic Joint Infections → Description
Septic arthritis in a prosthetic joint. May follow joint replacement within <3 months of replacement surgery (early infection)
Prosthetic Joint Infections → % of joint replacement that have infections
0.5-2% of all joint replacements
Prosthetic Joint Infections → Cause
Direct inoculation hence skin-type flora
Late – haematogenous
Biofilm produced on foreign material
Often multiple organism
