Infections Flashcards
What are the common organisms involved in Septic arthritis?
S. Aureus N Gonnorhoea Salmonella - sickle cell Bartonella - HIV Kingella + GBS in children
What organisms are involved in SA in IV drug users?
Pseudomonas
GNB
What is the pathophysiology behind the damage done to cartilage in SA?
Proteolytic enzymes are released from bacteria and synovium
IL 1
How does one diagnose septic arthritis?
WBC > 50 000 on fluid
Bone scan
What factors are involved in Kochers criteria?
- Weight bearing status
- Temp >38.5
- WBC count >12
- ESR >40
2 = 40% 3 = 93%
Common bony infections in dialysis patients?
Spine and Ribs
What are the 5 stages of biofilm formation?
- Adherence (reversible)
- Aggregation
- Biofilm formation
- Maturation
- Dispersion
What are the 2 anti-biofilm agents?
- Rifampacin - Gram Pos
2. Cipro - Gram Neg
What are the 2 characteristics of a biofilm?
Bacteria enter a sessile stage
Biofilm made from a Extracellular Polymeric Substance (EPS) - GLYCOLAX
What is the staging system of osteomyelitis and what 2 broad categories is it based on?
Cierny-Mader
Host and Anatomic location
What type of bacteria is TB?
Obligate aerobic acid fast bacilli
How is TB cultured?
Lowenstein-Jensen Medium
What does histology reveal in TB infection?
Granuloma
Casseating central necrosis
TB Treatment duration in bone/joint?
12-18 months
What are the 2 main mechanisms of action of anti-TB drugs?
Cell wall inhibition
Inhibition of cell protein synthesis
All of the 1st line TB drugs interfere with production of the cell wall except?
Rifampacin - inhibit mRNA transcription and translation
What 3 factors contribute to osteitis at the metaphysis?
Sluggish + turbulent blood flow
Low o2
Low ph
Septic arthritis CANNOT develop in which joint following osteitis?
Knee
What are the 3 most common pathogens for osteitis in kids?
- S AUREUS!!
- GBS in neonates
- Kingella
What is a Brodie’s abscess?
Chronic abscess surrounded by sclerotic bone
When is a bone scan indicated in osteomyelitis?
Need to localise infection in an infant/toddler with non-focal exam
What can increase the sensitivity of a MRI in Osteomyelitis?
Gadolinium
What are the 2 mechanisms of infection with hardware?
Seeding
Biofilm
What is the most sensitive test in hardware infections?
CRP - should decrease D2 post op
How long should DMARDs be stopped prior to replacement?
4-6/52
What markers should have normalised off antibiotics for revision arthroplasty?
ESR
CRP
What is the time to onset for acute periprosthetic infections?
<90 days from surgery
What is the difference between the acute and chronic periprosthetic infections?
Acute = no invasion into the prosthetic-bone interface
No biofilm production
Key radiographic findings in periprosthetic infections?
Generalised bone resorption without implant wear
What other 2 scans are used with periprosthetic infections?
- Bone scan - Tc-99m detects inflammation
In-111 - detects leukocytes
If infection suspected but cannot be confirmed via bloods/aspiration - PET
What criteria are used to diagnose periprosthetic infections?
- MSIS criteria
2 Major
2. Minor
What are the 2 most sensitive blood markers for prosthetic joint infection?
alpha defensin
IL 6
What is the treatment for acute (<3 weeks) periprosthetic infections?
Poly exchange with component retention and 4-6/52 abx
What are the 2 classes of antibiotics available in PMMA?
Aminoglycosides (Genta/Tobra)
Vancomycin
