Infections Flashcards
Which is the most common joint in which septic arthritis develops?
The knee
What is the most common bacteria to cause septic arthritis?
Staphylococcus aureus
What is a common cause in young adults who are sexually active?
Neisseria gonorrhoeae
Which bacteria is likely to cause septic arthritis in prosthetic joints?
Staph epidermidis
What bacteria can cause septic arthritis?
- Staphylococcus aureus
- Neisseria gonorrhoeae
- Staph epidermidis
- Lyme disease
- Haemophilus influenzae - used to be high in children but now vaccine for it
- Gram-NEGATIVE bacteria e.g. E.coli or Pseudomonas Aeruginosa in the elderly or very young or those who are systemically unwell/ IV drug user
What are the risk factors for septic artheritis?
- Prosthetic joints
- Diabetes mellitus
- Immunosuppression e.g. HIV
- Pre existing joint disease e.g. RA (10x)
- Low socioeconomic status
- Age <15 and >55
- IVDU (Intravenous Drug user)
- Osteomyelitis
- Intra-articular injection
- Recent joint surgery
What are the signs for septic arthritis?
- Red hot swollen joint, usually just one joint
- Tachy and feverish
What are the symptoms in the early infection with septic arthritis?
Wound inflammation/discharge, joint effusion, loss of function and pain
What are the symptoms in the late disease?
- Presents with pain or mechanical dysfunction
- Fluid accumulation leading to joint destruction
What would you see in the FBC?
Raised WCC
What will you see in the joint aspiration?
- Fluid will be purulent/opaque/thick/pussy due to the high WCC in it
What should normal joint aspiration fluid look like?
Yellow and quite thin
What would you see in the xray in septic arthritis?
Not much unless you can see loosening or bone loss around a previously well fixed implant
What is the main differential for crystal arthritis and what test therefore distinguishes the two?
Crystal arthritis and joint aspiration will show the crystals if not infection
What is the pharmacological treatment for septic arthritis?
IV antibiotics for 6-12 weeks
What type of bacteria are you targeting in septic arthritis?
Gram negative cocci
What antibiotic would you give in the majority of cases?
IV flucloxacillin (targets most gram negative)
What antibiotic would you give if allergic to penicillin?
Erythromycin
What antibiotic would you give for MRSA?
Vancomycin
What surgical options could be used in septic arthritis?
- needle aspiration to decompress the joint
- arthroscopic lavage
What is osteomyelitis defined as?
Infection of bone
Does osteomyelitis usually affect a single bone or multiple sites?
A single bone
How can you categorise osteomyelitis?
- Acute haematogenous
- Secondary to continuous local infection
- Direct inoculation from trauma or surgery
What does chronic osteomyelitis mean?
Bone necrosis (months to years)
What organisms are likely to cause osteomyelitis?
- Staph aureus - commonest cause
- Pseudomonas
- E coli
- Streptococci
What two routes can the bacteria spread via?
Direct or haematogenous
What does haematogenous spread mean?
Spreads to the bones via the blood
What bones are most likely to be affected by haematogenous spread in adults and in children?
- Children - long bones
- Adults - vertebrae
What is the necrotic bone referred to as?
The sequestrum
What is new bone formation called?
Involucrum
What is process that leads to new bone formation in osteomyelitis?
- Inflammatory exudate in the marrow
- Increased intramedullary pressure
- Extension of exudate into the bone cortex
- Rupture through the periosteum
- Interruption of periosteal blood supply
- Leaves pieces of seperated dead bone
- New bone forms here
What are the risk factors for osteomyelitis?
- Diabetes mellitus
- IV drug user
- Immunosuppression
How does osteomyelitis present?
- Non specific pain at the site of infection
- Fever, malaise, fatigue
- Local inflammation
- Wound drainage
- Reduced range of movement
What would you see on the blood test in osteomyeltistis?
Raised ESR/CRP and WCC
What is the gold standard investigation for osteomyelitis?
Bone biopsy with culture. Only 50% of cases will show on a blood culture
What would you see on the xray in osteomyelitis?
- cbone density changes aren't apparent for 10-14 days - Shows haziness and loss of - Subperiosteal reaction - Sequestrum and involucrum can be seen in later infection
Why is an MRI better then an xray?
- Shows inflammation better
- Shows changes 3-5 days as well as soft tissue involvement
What is the non-pharmacological treatment for osteomyelitis?
Bed rest if its spinal
What is the pharmacological treatment for osteomyelitis?
- Flucoxicillin or vancomycin for 6 weeks
What would you use if the infection was caused by TB?
Triple therapy
What surgical therapy can be done?
- Debridement
- Hardware replacement or removal
