Microbiology 8: Wound, Bone And Joint Infections Flashcards
What are the 3 main organisms causing surgical site infections ?
Staphylococcus aureus
E.Coli
Pseudomonas aeruginosa
Does shaving a patient using a razor increase or decrease the risk of surgical site infection ?
Increase- you are making micro-abrasions which can be an entry route for skin bacteria.
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
B
List 3 bacterial factors that contribute to the risk of septic arthritis ?
S.Aureus- fibronectin binding proteins
S.Aureus- Panton-Valentine leucocidin
Kingella kingae- bacterial pili
Which bacterial factor is associated with more fulminant septic arthritis ?
Panton-valentine Leukocidin (S.aureus)
Which organism is the most common cause of septic arthritis ?
S.aureus
What is the most common organism responsible for vertebral osteomyelitis ?
S.aureus
Which part of the spine is most commonly affected in vertebral osteomyelitis ?
A)Cervical B)Thoracic C) Lumbar D)Sacral E)coccyx
C
What is the diagnostic investigation for vertebral Osteomyelitis ?
MRI scan
Which techniques are used to treat Chronic osteomyelitis ?
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.
What characteristic radiological finding of Prosthetic joint infection ?
Loosening (bone loss along the cement-bone interface)
What is the treatment for prosthetic joint infection ?
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.
Which organism is the most common cause of Prosthetic joint infection ?
Coagulase negative staphylococci - Staphylococcus epidermidis
how many organisms must a surgical site be contaminated with to increase the risk of SSI
> 10^5 microorganisms
dose of contaminating material is much lower where there is foreign material present
what are the 3 levels of SSI
superficial incisional - skin and subcutaneous tissue
deep incisional - fascial and muscle layers
organ/space infection - any part of the anatomy other than the incision
name a gram positive coccus which is haemolytic and causes SSI
MRSA
treat with IV linezolid
what factors increase your risk of getting a SSI
age (independent RF) diabetes malnutrituin radiotherapy and steroids rheumatoid arthritis obesity smoking
why is nasal contamination done pre surgery
done if a patient is found to have S. Aureus in their nostrils
what antiseptics are used to prepare the skin pre-surgery
povidine - iodine
chlorhexidine 70% alcohol
features of septic arthritis
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
what organisms commonly cause septic arthrits
S. aureus
Streptococci
gram -ves: E. Colid, haemophilus influenzae, nisseria gonorrhoeae
clinical features of septic arthritis
1-2 w history of red, painful, swollen joint with restricted movement
monoarticular in 90%
investigations for septic arthritis
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
management of septic arthritis
antibiotics via OPAT (outpatient parenteral antimicrobial therapy) drainage of the joint
what causes vertebral osteomyelitis
acute haematogeous spread (bacteraemia)
exogenous (eg implantation during disc surgery)
what organisms cause vertebral osteomyelitis
staph aureus
coagulase-negative staphylococcus
gram-negative rods
streptococcus
what is the most common site for vertebral osteomyelitis
lumbar
cervical
cervico-thoracic
symptoms of vertebral osteomyelitis
back pain
fever
neurological impairment
treatment for vertebral osteomyelitis
antibiotics - at least 6 weeks
treatment for chronic osteomyelitis
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
clinical features of prosthetic joint infection (PJI)
pain
persistent complaint that the joint was ‘never right’
early failure
sinus tract
causative organisms for PJI
coagulase negative staphylococci
streptcocci
enterococci
diagnosis of PJI
radiology - loosening - bone loss along the cement-bone interface
CRP>13.5 for prosthetic knee joint
CRP>5 for hip
joint aspiration
Treatment for PJI
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
