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
