Lecture 18: Septic arthritis and rheumatic fever

Question 1

Potential differential diagnosis’s for hot swollen knee joint

Answer 1

• Septic arthritis
• rheumatic fever
• other: reactive arthritis, trauma

Question 2

Gram stain revision

Answer 2

Gram +: Streptococci: alpha haemolytic: pneumoniae, Beta: pyogenes; staphyococci
Gram -: Nesseria meninigitidis

Gram + bacillus: Clostridium, listeria
Gram - bacillus: Haemophillus influenzae, enteric pathogens e.coli, salmonella

Question 3

What diseases can group A strep cause?

Answer 3

Acute pyogenic/suppurativeinfections: 
-tonsilitis 
-pharyngitis
-scarlet fever
-septic arthritis
*Non suppurative/inflammatory sequelae:
Acute rheumatic fever/RHD
post streptococcal glomerulonephritis

Question 4

Septic arthritis

note most common cause staph then strep

Answer 4

• Occurs often in childhood (bone growing –> increase blood flow)
• occurs with fever and malaise
• swelling, erythema
• Joint held in position that maximise joint capsule volume: Flexed knee, flexed abducted ext rotated hip
• Joint aspirate
• Must be diagnosed quick to prevent any growth plate disruption

Question 5

Septic arthritis management

Answer 5

Joint washouts
IV antibiotics
Then oral course, total a few weeks

Question 6

What is acute rheumatic fever?

Answer 6

• AI response following throat infection with Strep pyogenes
• Generalised inflammation; attacking certain parts of the body - heart,skin,joints
• can cause lasting damage heart valves = Rhuematic heart disease

Question 7

Jones criteria

Answer 7

Used to diagnose rheumatic heart disease.
diagnosis requires 2 Major or 1 major and 2 minor criteria
Major: Carditis, polyarthritis (asymmetircal and migratory), sydenhams chorea (dance like movements remeber little girl in video) , erythema marginatum (line shaped rash)
Minor: fever, polyarthrlagia, raised CRP or ESR, prolonged PR on ECG

Question 8

How does RF occur

Answer 8

Autoimmune mechanism where antibodies created against strep interact with similar host proteins. e.g M protein and cardiac myosin

Question 9

Importance of strep antibody titres

Answer 9

Neede to confirm recent strep infection. Those with ARF have much higher.
Use ASO (antistreptolysin) and anti-DNAse B titres.

Question 10

Preventing RF and managing

Answer 10

managing: best rest, monitor systemic inflammation (CRP)IM penicillin every 4 weeks for next ten years

Preventing: Penicillin

Question 11

Septic arthritis vs RF

Answer 11

Septic arthritis: Any age group, acute active infection, arthritis due to bacteria in joint, staph or strep, treat with cleaning and antibiotic (aqueous penicillin G, then IM benzathine penicillin G)

RF: school age 5-15, AI, multisystem, penicillin used long term