Microbiology 8: Wound, Bone And Joint Infections Flashcards

1
Q

What are the 3 main organisms causing surgical site infections ?

A

Staphylococcus aureus
E.Coli
Pseudomonas aeruginosa

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2
Q

Does shaving a patient using a razor increase or decrease the risk of surgical site infection ?

A

Increase- you are making micro-abrasions which can be an entry route for skin bacteria.

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3
Q

Which of the following is associated with a reduced risk of surgical site infections ?

A) Obesity
B)bactericidal concentration of antibiotics in the serum at time of incision
C)Smoking
D) Diabetes

A

B

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4
Q

List 3 bacterial factors that contribute to the risk of septic arthritis ?

A

S.Aureus- fibronectin binding proteins
S.Aureus- Panton-Valentine leucocidin
Kingella kingae- bacterial pili

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5
Q

Which bacterial factor is associated with more fulminant septic arthritis ?

A

Panton-valentine Leukocidin (S.aureus)

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6
Q

Which organism is the most common cause of septic arthritis ?

A

S.aureus

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7
Q

What is the most common organism responsible for vertebral osteomyelitis ?

A

S.aureus

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8
Q

Which part of the spine is most commonly affected in vertebral osteomyelitis ?

A)Cervical
B)Thoracic 
C) Lumbar
D)Sacral
E)coccyx
A

C

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9
Q

What is the diagnostic investigation for vertebral Osteomyelitis ?

A

MRI scan

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10
Q

Which techniques are used to treat Chronic osteomyelitis ?

A

Lautenbach technique- debridement of infected/dead bone and insertion of 2 drains that allow delivery of antibiotics, fluids and irrigation.

Papineau technique- complete excision of infected tissue and necrotic bone followed by cancellous bone grafting and skin grafting.

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11
Q

What characteristic radiological finding of Prosthetic joint infection ?

A

Loosening (bone loss along the cement-bone interface)

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12
Q

What is the treatment for prosthetic joint infection ?

A

Single stage revision- The old prosthesis and all infected/necrotic tissue and bone is debrided. A new prosthesis is put in place with antibiotics.

Two stage revision- The old prosthesis and all the infected/necrotic bone and tissue is debrided. A spacer is put in and the area is treated for 6 weeks with Antibiotics before a new prosthesis is put in place.

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13
Q

Which organism is the most common cause of Prosthetic joint infection ?

A

Coagulase negative staphylococci - Staphylococcus epidermidis

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14
Q

how many organisms must a surgical site be contaminated with to increase the risk of SSI

A

> 10^5 microorganisms

dose of contaminating material is much lower where there is foreign material present

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15
Q

what are the 3 levels of SSI

A

superficial incisional - skin and subcutaneous tissue
deep incisional - fascial and muscle layers
organ/space infection - any part of the anatomy other than the incision

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16
Q

name a gram positive coccus which is haemolytic and causes SSI

A

MRSA

treat with IV linezolid

17
Q

what factors increase your risk of getting a SSI

A
age (independent RF)
diabetes 
malnutrituin 
radiotherapy and steroids 
rheumatoid arthritis 
obesity 
smoking
18
Q

why is nasal contamination done pre surgery

A

done if a patient is found to have S. Aureus in their nostrils

19
Q

what antiseptics are used to prepare the skin pre-surgery

A

povidine - iodine

chlorhexidine 70% alcohol

20
Q

features of septic arthritis

A

more common in people with rheumatoid arthritis
organisms
Staph aureus - fibronecting binding protein
Kingella Kingae - adherence via bacterial pili
strains of S. Aureus produce PVL (panton-valentine leukocidin), associated with fulminant infections

21
Q

what organisms commonly cause septic arthrits

A

S. aureus
Streptococci
gram -ves: E. Colid, haemophilus influenzae, nisseria gonorrhoeae

22
Q

clinical features of septic arthritis

A

1-2 w history of red, painful, swollen joint with restricted movement
monoarticular in 90%

23
Q

investigations for septic arthritis

A

blood cultures BEFORE antibiotics
synovial fluid aspiration - send for mc+s
synovial count >50,000 WBC/ml suggest septic arthritis
US
CT - erosive bone change
MRI - joint effusion, articular cartilage destruction

24
Q

management of septic arthritis

A
antibiotics 
via OPAT (outpatient parenteral antimicrobial therapy)
drainage of the joint
25
Q

what causes vertebral osteomyelitis

A

acute haematogeous spread (bacteraemia)

exogenous (eg implantation during disc surgery)

26
Q

what organisms cause vertebral osteomyelitis

A

staph aureus
coagulase-negative staphylococcus
gram-negative rods
streptococcus

27
Q

what is the most common site for vertebral osteomyelitis

A

lumbar
cervical
cervico-thoracic

28
Q

symptoms of vertebral osteomyelitis

A

back pain
fever
neurological impairment

29
Q

treatment for vertebral osteomyelitis

A

antibiotics - at least 6 weeks

30
Q

treatment for chronic osteomyelitis

A

radical debridement down to living bone
remove sequestra (dead bone tissue) and infected bone and soft tissue
lautenbach technique - debridement and collection of multiple samples for culture and histology
Papineau technique - complete excision of infected tissue and necrotic bone

31
Q

clinical features of prosthetic joint infection (PJI)

A

pain
persistent complaint that the joint was ‘never right’
early failure
sinus tract

32
Q

causative organisms for PJI

A

coagulase negative staphylococci
streptcocci
enterococci

33
Q

diagnosis of PJI

A

radiology - loosening - bone loss along the cement-bone interface
CRP>13.5 for prosthetic knee joint
CRP>5 for hip
joint aspiration

34
Q

Treatment for PJI

A

single stage revision:

  • remove all foreign material and dead bone
  • re-implant new prosthesis with antibiotic impregnated cement and give IV antibiotics

2 stage revision:

  • remove prosthesis and put in a spacer
  • period of IV antibiotics (for 6 weeks)
  • re-debride and sample at 2nd stage