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11. CP - Diseases of the musculoskeletal system > (56) Bone and joint infections > Flashcards

(56) Bone and joint infections Flashcards

(58 cards)

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1
Q

What is infection of bone known as?

A

Osteomyelitis

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2
Q

Give 3 features of osteomyelitis?

A
  • heterogeneous disease (diff pathogens, diff sites, diff clinical contexts)
  • difficult to diagnose in some cases
  • difficult to treat
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3
Q

State 3 methods of pathogenesis of osteomyelitis

A
  • haematogenous
  • contiguous-focus
  • direct inoculation
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4
Q

Describe how haematogenous spread may cause osteomyelitis

A

Bacteria shed into the blood stream from other infection eg. endocarditis, and then seeds bone - infants and children

vertebral body osteomyelitis usually haematogenous

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5
Q

What does contiguous-focus cause of osteomyelitis mean?

A

Spread from adjacent area of infection (focus of infection next to bone, can spread into bone)

eg. diabetic foot - deep infection around ulcers spreads to bone

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6
Q

How can osteomyelitis be caused by direct inoculation?

A

Through trauma or surgery

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7
Q

State the 4 stages of classification of osteomyelitis

A
  • stage I medullary
  • stage II superficial
  • stage III localised
  • stage IV diffuse
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8
Q

What does stage I medullary osteomyelitis mean?

A

Necrosis of medullary contents/endosteal surface - confined to medulla of bone - haematogenous

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9
Q

What does stage II superficial osteomyelitis mean?

A

Necrosis limited to exposure surface, periosteum disrupted - contiguous - eg. diabetic foot, sacral pressure sore infection in elderly

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10
Q

What does stage III localised osteomyelitis mean?

A

Full thickness cortical sequestration, stable before and after debridement (trauma/stage I or II evolving)

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11
Q

What does stage IV diffuse osteomyelitis mean?

A

Extensive, unstable bone

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12
Q

What is debridement?

A

The process of removing dead (necrotic) tissue or foreign material from and around a wound to expose healthy tissue

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13
Q

If infected bone is necrotic and lacks blood supply, how does this cause trouble with treatment?

A

Can’t deliver antibiotics are they are delivered via the blood stream, need surgery to get rid of the infected bone

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14
Q

How does osteomyelitis present clinically?

A
  • pain that is localised, constant and progressing (and nocturnal)
  • soft tissue swelling
  • erythema
  • warmth
  • localised tenderness
  • reduced movement of affected limb
  • systemic flu-like symptoms (fever, chills, night sweats, rigor)
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15
Q

Clinical presentation of osteomyelitis varies with which factors?

A
  • age
  • type of infecting organism
  • location of infection
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16
Q

What is the most common causative organism of osteomyelitis?

A

Staphylococcus aureus (at least 60%)

  • especially haematogenous
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17
Q

Give some other causative organisms of osteomyelitis (other than staph. aureus)

A
  • streptococci (group A and B)
  • enterococci
  • gram negative bacilli
  • anaerobes
  • mycobacterium tuberculosis, brucella spp.
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18
Q

Give some examples of gram negative bacilli that may cause osteomyelitis

A
  • slamonella spp.
  • klebsiella spp.
  • pseudomonas aeruginosa

(in premature babies, IVDU, sickle cell disease)

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19
Q

Myco. TB can cause indolent osteomyelitis, particularly where?

A

In the vertebral bodies

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20
Q

What is the gold standard test for osteomyelitis?

A

Cultures and histology of bone biopsy/needle aspirate (needle into bone or area of adjacent pus)

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21
Q

Other than culture and histology, what are other tests used in osteomyelitis diagnosis?

A
  • superficial swabs
  • leukocytosis (not diagnostic)
  • C-reacitve protein (usually raised, monitor response to therapy)
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22
Q

Why are superficial swabs not very useful in diagnosing osteomyelitis?

A

Limited value in contiguous-focus infections as will grow lots of different bacteria, including normal bacteria on skin etc.

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23
Q

What is the therapy for osteomyelitis?

A

Antimicrobials +/- surgery depending on site/stage

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24
Q

What type of antimicrobial treatment should you avoid in osteomyelitis?

Study These Flashcards
A

Avoid empirical antimicrobial therapy if possible - give directed antimicrobial therapy guided by causative organism

25
Antimicrobials should be administered by which route initially in osteomyelitis?
Intravenous - this ensures compliance and optimal bone levels - penetration into bone is low orally
26
Which antibiotics achieve acceptable levels in bone and so can be used in osteomyelitis?
- clindamycin - ciprofloxacin - vancomycin - B-lactams - gentamicin
27
What is the antimicrobial of choice for S. aureus OM in patients who are not penicillin-allergic?
Flucloxacillin IV
28
Vancomycin is often used for OM when?
When the patient has a penicillin allergy
29
Vancomycin is effective against which type of bacteria?
Gram-positive (staphylococci, streptococci, enterococci - has to be given IV)
30
Gentamicin is effective against which type of bacteria?
Gram-negative
31
What is septic (infective) arthritis?
Inflammatory reaction in joint space (arthritis) caused by infection - result from direct invasion of the joint
32
How is septic arthritis classified?
- native (natural) joint infection | - prosthetic (artificial) joint infection (early/late)
33
Describe the pathogenesis in native joint infection
- organisms enter a joint via the blood (haematogenous) or trauma (surgery or injection) - cartilage erosion causes joint space narrowing/impaired function
34
What about native joint infection causes impaired function?
Narrowing of the joint space caused by cartilage erosion by the infection
35
What are the predisposing factors of native joint infection?
- rheumatoid arthritis - trauma - intravenous drug use - immunosuppressive disease
36
Is native joint infection associated with mortality?
Low mortality condition but with significant dysfunction - unless it causes severe sepsis and then it is associated with mortality
37
Describe the pathogenesis of prosthetic joint infection
- organisms enter a joint via the blood (haematogenous), during surgery or following wound infection - joint prosthesis and cement provide a surface for bacterial attachment - polymorph infiltration results in tissue damage instability of the prosthesis
38
How do polymorphs cause damage to joint and instability in prosthetic joint infection?
Polymorphs try to phagocytose the bacteria but cannot - so they give out lytic enzymes which cause damage to the joint
39
What are the predisposing factors to prosthetic joint infection?
- prior surgery at site of prosthesis - rheumatoid arthritis - corticosteroid therapy - diabetes mellitus - poor nutritional status - obesity - extremely advanced age
40
What are the clinical features of septic arthritis?
- joint pain, swelling, tenderness, redness, and limitation of movement - systemic upsets like fever, chills, night sweats
41
Symptoms of septic arthritis depend on what?
Duration of symptoms is variable and influences by site of infection, type of joint (native vs. prosthetic) and causative organisms
42
What are the causative bacteria of native joint infections?
- staph. aureus - strep. A/B/C/G - haemophilus influenzae - gram neg bacilli - neisseria gonorrhoea - neisseria meningitidis - anaerobes - mycobacteria
43
What are the causative bacteria in prosthetic joint infections?
- staph. aureus - coagulase negative strep (CoNS) - step A/B/C/G - enterococci - gram neg bacilli - corynebacteria - propionibacteria etc
44
Other than bacteria, what else can cause septic arthritis?
- fungi eg. Candida spp. | - viruses eg. parovirus B19, rubella virus, mumps virus (usually self-limiting)
45
How is a joint aspirate examined in diagnostics?
- total white cell count - differential WCC - gram stain - crystal examination - culture - PCR
46
WCC is normally what in infection?
Over 40,000/mm3 during infection - but raised in lots of things, not just septic arthritis
47
What would a differential WCC show in infection?
Over 75% polymorphs during infection
48
Why is gram stain not a very good test for septic arthritis?
Not very reliable (35-65% positive)
49
What does doing a culture in septic arthritis allow?
Allows change from empirical therapy to direct therapy
50
Describe the therapy for native joint infection
- removal of purulent material (joint drainage/washout) - empirical IV antimicrobial therapy if required - direct IV antimicrobial therapy depending on causative organism and susceptibility
51
How long is a native joint infection treated for?
2-4 weeks
52
Which antimicrobial is used for native septic arthritis caused by S. aureus?
Flucloxacillin
53
What should be done before empirical therapy is started for septic arthritis?
Take microbiology samples
54
Describe the therapy for prosthetic joint infections
- removal of implant or replacement of some elements, washout - empirical IV antimicrobial therapy if required - directed IV antimicrobial therapy depending on causative organism and susceptibility
55
How long is a prosthetic joint infection treated for?
6 weeks (more complicated - so longer treatment) NB. oral switch (OVIVA)
56
Which antimicrobials would you use for staph. aureus prosthetic joint infection?
Flucloxacillin plus rifampicin (never give rifampicin on its own to treat S. aureus as often develops resistance)
57
Which antimicrobials would you use to treat CoNS prosthetic joint infection?
Vancomycin IV plus rifampicin
58
What is the most common bacterial pathogen causing septic arthritis?
Staphylococcus aureus

11. CP - Diseases of the musculoskeletal system (4 decks)

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