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Microbiology Flashcards

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1
Q

Which bones does osteomyelitis usually occur in

A

One of the long bones

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2
Q

What are some of the classifications of osteomyelitis

A

Acute or chronic - refers to speed of onset

Contiguous or haematogenous - either spread locally or through blood

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3
Q

How can osteomyelitis infection present

A

As micro abscess in the metaphis

Or as a infected pus filled abscess

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4
Q

How do you diagnose osteomyelitis

A

Clinical suspicion from history and examination
Can take swab to help pick treatment - not always diagnostic
GOLD STANDARD - bone biopsy

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5
Q

Why is swabbing a site of osteomyelitis not always useful

A

warm wet place so will have bugs growing that may not be causing issue
Not always diagnostic

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6
Q

What is the best imaging technique for osteomyelitis

A

MRI scan

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7
Q

How do you treat osteomyelitis

A

Surgical debridement to remove infected tissue

Antimicrobials to back up - wait for microbiology results

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8
Q

Do you ever start empirical antimicrobial treatment for osteomyelitis

A

ONLY if there are signs of sepsis

Otherwise wait for microbiology results

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9
Q

How long does it take to treat osteomyelitis

A

In general 6 weeks

This is because debrided bone takes 6 weeks to be covered by vascularised soft tissue

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10
Q

What is the antibiotic of choice for staph aureus

A

flucloxacillin

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11
Q

What is an obvious clinical sign of osteomyelitis

A

If you can see tendon or probe a bone

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12
Q

How can open fractures lead to osteomyelitis

A

Contiguous infection
Bone is open to air etc
Common pathogens are staph aureus and aerobic gram negatic bacteria

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13
Q

What is the key sign that a fracture has become infected

A

non-union of bone and poor wound healing

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14
Q

What are some features of diabetic foot

A 
Micro neurovascular dysfunction 
Ischaemia 
Diminished sensation
Deformity in toes and 
arch 
Ulceration
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15
Q

What feature of a diabetic foot commonly leads on to osteomyelitis

A

Ulcers

Probe to bone is the best sign as diagnosis can be hard

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16
Q

What is the best way to determine the bacterial cause of osteomyelitis

A

A bone biopsy

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17
Q

What types of bacteria does gentamicin treat

A

Gram negative

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18
Q

How long is antibiotic treatment for skin and soft tissue infection

A

7 days

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19
Q

How long is antibiotic treatment for blood

infection

A

14 days

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20
Q

Which antimicrobials might you use to treat osteomyelitis

A

Gram + cover: flucloxacillin (vancomycin if pen allergic)
Oral switch to doxycycline
Gram -ve cover: gentamicin IV if severe

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21
Q

Why do you switch to oral doxycycline rather than oral flucloxacillin in osteomyelitis

A

Bone penetration of doxy is great

Fluclox has poor bone penetration

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22
Q

Which groups are most likely to get haematogenous osteomyelitis

A

Prepubertal children
PWID
Central lines, dialysis patients, elderly

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23
Q

What would you do if a central line led to haematogenous osteomyelitis

A

Remove the line immediately

Keep doing blood cultures and treat until you get a negative result

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24
Q

What are the key pathogens for haematogenous osteomyelitis in PWIDs

A

Staph and Strep
Particularly aureus and viridans respectively

More likely to have unusual pathogens

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25
What sites are common for PWIDs to develop infection
In unusual sites with unusual pathogens Sternoclavicular Sternochondral joints, Sacroiliac joint Pubic symphysis
26
What is the most common pathogen to cause haematogenous osteomyelitis in dialysis patients
Staph aureus - due to colonisation | Aerobic gram negatives
27
What is clavicle ostemyeltis
A rarer site of the infection | Often caused by neck surgery or subclavian vein catheritsation
28
What is osteitis pubis
Another unusual site of bone inflammation Occurs in the pubic bones Can be triggered by surgery and its seen in athletes
29
Describe sickle cell osteomyelitis
Common infectious complication in those with sickle cell anaemia - 12% Get acute long bone osteomyelitis
30
What are the most common pathogens in sickle cell osteomyelitis
Salmonella | Staphylococcus aureus
31
What is Gaucher's disease
Lysosomal storage disorder - affects tibia May mimic bone crisis Usually sterile but can be infected by staph aureus
32
What are SAPHO and CRMO
Synovitis Acne Pustolosis Hyperostosis Osteitis Chronic Recurrent Multifocal Osteomyelitis Both unusual and rare conditions
33
What are the symptoms of SAPHO and CRMO
Fever, weight loss, generalised malaise | Multifocal osteitis
34
How does vertebral osteomyelitis usually occur
Mostly spreads through the blood - haematogenous
35
What are some potential causes of vertebral osteomyelitis
``` Epidural or Psoas abscesses PWID IV sites STIs or GU infections Post-op ```
36
What are some symptoms of vertebral osteomyelitis
Fever Pain and tenderness Raised inflammatory markers Neurological symptoms
37
How do you diagnose vertebral osteomyelitis
Biopsy | May need to do several or progress to open biopsy
38
How do you treat vertebral osteomyelitis
Drain any abscesses | Put onto antimicrobials for 6 weeks
39
Do you need to have pulmonary TB to get it in the spine (or other bones)
No | Less than half presenting with vertebral TB have the lung condition
40
What are the risk factors for infection in prosthetic joints
Rheumatoid arthritis Diabetes Obesity Malnutrition
41
How can a prosthetic joint become infected
Direct inoculation of pathogen at time of surgery Due to joint manipulation in surgery Seeding of joint at later time e.g. via blood
42
What is a common sign of prothesis becoming infected
Signs at the wound site and the wound opening up again
43
What conditions can be caused by PVL producing staph aureus
Skin infections Necrotising pneumonia Invasive infection
44
How do you treat PVL producing staph aureus infections
Flucloxacillin, clindamycin, linezolid, depending on sensitivities
45
What is the best way to treat a prothesis infection
Remove the prosthesis Give antimicrobial therapy for at least 6 weeks Replace if possible
46
How do you diagnose prosthesis infections
Culture samples taken during operation Blood culture CRP Radiology
47
Which STI can cause septic arthritis
Gonorrhoea | Neisseria gonorrheae
48
How do you treat septic arthritis
Start empirical treatment with flucloxacillin (high dose) | Alter if needed when you confirm the organism
49
What is pyomositis
Bacterial infection of the skeletal muscles which results in a pus-filled abscess 90% staph cuased Common in temperate areas and the immunosuppressed
50
How do you treat pyomyositis
Multidisciplinary approach - plastics, orthopaedics, infection Needs wide local excision Antibiotics often don't help
51
How do you treat tetanus
``` Surgical debridement. Antitoxin Supportive measures such as intubation, beta blocker etc Antibiotics- penicillin / metronidazole Booster vaccination ```
52
What are the 5 key signs of infection
``` Rubor - redness Calor - heat Dolor - pain Tumour - swelling Loss of function ```
53
When should you start antibiotic treatment
ONLY once you know which bug you are treating - wait for culture and lab confirmation EXCEPTION is if sepsis or meningitis is suspected, therefore empirical treatment may be life saving
54
What are some useful blood tests in infection
C -reactive protein - inflammatory marker that can be sensitive to infection Plasma viscosity Occasionally blood cultures, WCC and ESR
55
This
Mostly post-traumatic - e.g. open fractures Then occurs in children Immunosuppression
56
How must you treat a bone infection when there is pus present
Must physically remove the pus and any dead material from the area Antibiotics will not get rid of pus
57
What is an involucrum
This is formed when infection gets under the periosteum and raises it up New bone forms from this periosteum and starts a new layer Occurs in chronic osteomyelitis
58
How does septic arthritis occur
Infection gets into joint via inoculation Spreads from the metaphysis of bone Spreads through the blood
59
Describe necrotising fasciitis
``` Soft tissue infection Life-threatening Often occurs in the immunocompromised Bacteria may produce gas that gets into the tissue Needs emergency surgery ```
60
What tests would you do if you suspected infection in a replacement joint
CRP Joint aspiration Bone scan X ray
61
What prophylaxis can be given against infection during/after surgery
Clean air theatres Hand hygiene Local antibiotics - in bone cement Systemic antibiotics - IV
62
Which bugs do you normally use prophylaxis for after surgery
Staph aureus | Staph epidermidis

MSK (21 decks)

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