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Cardio > Microbiology Bone and Joint infections > Flashcards

Microbiology Bone and Joint infections Flashcards

1
Q

Osteomyelitis Description

A

A progressive infectious process resulting in inflammatory destruction, bone necrosis (sequestrum) and new bone formation (involcrum). Can be acute or chronic

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2
Q

Osteomyelitis Pathogenesis requires

A

High innocula
Trauma
Or foreign material

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3
Q

Osteomyelitis 3 Types

A

Haematogenous
Contiguous
Diabetic

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4
Q

Osteomyelitis Haematogenous

A

Following bacteraemia, especially in children, metaphyseal area of long bones

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5
Q

Osteomyelitis Contiguous

A

After trauma o surgery or overlying soft tissue infection.

May be associated with prosthesis/pins/plates

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6
Q

Osteomyelitis Diabetic osteomyelitis

A
  • A consequence of reduced vascularity, neuropathic skin changes, decreased local immunity and metabolic disturbance
  • Often associated with foot ulcer (s)
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7
Q

Osteomyelitis Diabetic osteomyelitis assume and treatment

A

Assume osteomyelitis if bone evident at the base of ulcer

Often results in amputation

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8
Q

Osteomyelitis Signs and Symptoms

A

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

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9
Q

Osteomyelitis X-ray findings

A

Periosteal thickening/elevation on Xray

Lysis and sclerosis

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10
Q

Osteomyelitis Investigations

A 
Blood cultures, FBC, CRP
Deep tissues from theatre
Sinus swabs NEVER
Wound swabs – may be heavily colonised
Imaging
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11
Q

Osteomyelitis Treatment

A

Give antibiotics after organism found

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12
Q

Osteomyelitis Pathogens

A

Staphylococcus aureus – most common
→ has receptors ‘adhesins’ – for bone matrix, collagen-binding adhesion (cartilage) fibronectin-binding adhesins – 9foreign material)

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13
Q

Septic Arthritis → Description

A

Infection of joint space haematogenous or contiguous

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14
Q

Septic Arthritis →Most commonly seen in

A

Hip or Knee

Usually mono-articular

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15
Q

Septic Arthritis →Predisposition

A

Rheumatoid Arthritis

Joint Disease

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16
Q

Septic Arthritis →Pathogenesis

A

Synovial membrane highly vascular
Local polymorphonuclear response
→ Release of proteolytic enzymes and bacterial toxins
→ Rapid cartilage destruction, joint effusion
→ Decreases blood supply

17
Q

Septic Arthritis → Complications

A

Decreased function of joint, if not treated promptly

18
Q

Septic Arthritis → Signs and Symptoms

A

Painful hot swollen joint +/- malaise, pyrexia

Unable to weight bear, decrease range of movement

19
Q

Septic Arthritis → Pathogens

A
  • 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
20
Q

Reactive Arthritis → Description

A
  • May occur following infectious diarrhoea e.g. Salmonella, Campylobacter, Yernisina and Shigella.
  • Also following Chlamydia, gonorrhoea (Reiters syndrome), hepatitis B.
21
Q

Reactive Arthritis → Investigations

A
  • Bacteria are not cultured from the joint arthritis is an inflammatory reaction
  • Serology or recent +ve stool cultures/GU swabs confirm diagnosis
22
Q

Prosthetic Joint Infections → Description

A

Septic arthritis in a prosthetic joint. May follow joint replacement within <3 months of replacement surgery (early infection)

23
Q

Prosthetic Joint Infections → % of joint replacement that have infections

A

0.5-2% of all joint replacements

24
Q

Prosthetic Joint Infections → Cause

A

Direct inoculation hence skin-type flora
Late – haematogenous
Biofilm produced on foreign material
Often multiple organism

25
Q

Prosthetic Joint Infections → Biofilm formation

A
  • Many/most infection now believed to involve biofilms
  • Complex communities of surface-associated cells in an extracellular matrix
  • Physical protection from antibiotics
  • Biofilm cells change their phenotype (may be less susceptible)
26
Q

Prosthetic Joint Infections → Diagnosis

A
  • History, examination, ESR, CRP, X-rays, isotope, scanes, MC &S of joint aspirate
  • Stain of sample
27
Q

Prosthetic Joint Infections → Treatment

A
  1. Conservative – washout, debride, retain joint + systemic antibiotics
  2. Radiacl i.e. remove prosthesis
  3. Lifelong suppressive therapy if unfit for surgery 30-60% patients retain useful joint function.
  4. Do nothing – if elderly comorbidities and current symptoms do not impact on quality of life
28
Q

Prosthetic Joint Infections → Treatment without removal

A

• Surgical drainage + 6 weeks antibiotics

29
Q

Prosthetic Joint Infections → 1 stage replacement

A
  • Removal and replacement at the same operation (+ antibiotic loaded cement)
  • 70-80% success
  • May be suitable for patients unfit for 2 operations
30
Q

Prosthetic Joint Infections → Stage 2

A
  • Removal followed by 6 weeks antibiotics (+/- cement spacer impregnated) then re-implantation
  • 90-95% success rate
  • May require plastic surgery, skin and muscle flaps
31
Q

Diagnosis of Bone and Joint infection → Diagnosis method

A
  • Blood cultures, FBC , CRP
  • Pus/joint fluid/bone specimens (Before treatment)
  • Multiple specimens for PJI or osteomyelitis
  • Imaging – Xrays, Ultra-sound, MRI, bone scans
  • (Serology if reactive arthritis, antistaphylococcal titres may be useful)
  • Review previous bacteriology if recurrent problem
32
Q

Diagnosis of Bone and Joint infection → Treatment pharma

A
  • Combination therapy PJI
  • 2-3 weeks for septic arthritis
  • 4 weeks for paediatric osteomyelitis
  • 6-8 + weeks for adult osteomyelitis and PJI
33
Q

Diagnosis of Bone and Joint infection → Treatment other

A
  • Drainage of effusions/pus is essential – also provides specimen for diagnosis
  • Debridement of all infected bone essential to Rx osteomyelitis (ex paediatrics)
  • Removal of prosthetics joint is usually required to effectively clear infection
  • NB. It is rarely necessary to start antibiotics immediately in a patients with PJI or chronic osteomyelitis – get appropriate samples for culture first
34
Q

Diagnosis of Bone and Joint infection → organisms to think of

A
  • S aureus
  • MRSA
  • Streptococci
  • Coliforms
  • Pseudomonas –
35
Q

S aureus antibiotics

A

flucloxacillin _ rifampicin, fusidic acid or gentamicin

36
Q

MRSA antibiotics

A

vancomycin + rifampicin or fusidic acid

37
Q

Streptococci antibiotics

A

benzyl penicillin or cefuroxime

38
Q

Coliforms antibiotics

A

consider ciprofloxacin

39
Q

Pseudomonas – antibiotics

A

ciprofloxacin/ceftazidine + gentamicin initially – NB check sensitivities

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