Lecture 18 - Septic arthritis and Rheumatic fever

Question 1

Group A Streptococcal disease

Answer 1

• tonsilitis/pharyngitis
• skin - empetigo, cellulitis
• scarlet fever
• bloodstream infection
• septic arthritis
• necrotising fascitis
• pneumonia/empyema
• myositis
• toxi shock syndrome
• puerperal sepsis
• can have delayed sequalae following uncomplicated infections
• can cause acute rheumatic fever, rhuematic heart disease or streptococcla glomerulonephritis

Question 2

Septic arthritis

Answer 2

• presence of infection from bacteria in bone and marrow
• occurs mainly in chlidren (high vasculature while it is growing)
• general symptoms include fever and unwellnes
• swelling, erythema, tenderness around affected d joint

arthritis - limitation of movement, hot joint, pain or tender to palpate

-knee joint easy to assess

Question 3

what is most common cause of joint infection

Answer 3

-staphylococcus aureus

2nd most common cause Streptococcus pyogenes

Question 4

Main points about septic arthritis

Answer 4

• needs to be diagnosed quickly as early treatment prevents complications such as irreversible damage from growth plate disruption
• ealry diagnosis is hard to see
• knee, hip and ankle most common joints
• 2 most common - staph aureus and streptococcus pyogens
• drainage and wash out of septic joint is often needed for diagnosis and treatment
• IV antibiotics are needed initially and total corse is likley to be 2-3 weeks

Question 5

Rhematic fever

Answer 5

• auto-immune response following throat infection after pharyngitis with streptococcus pyogens
• inflammation, attacking certain parts of body - heart, joints, skin/brain
• can cause lasting damage to mitral and aortic valves (rhematic heart disease)

-get infection with group A strep, then latent period for several weeks then symptoms of RHD occur

Question 6

Major and minor criteria for rheumatic fever

Answer 6

Need 2 major or 1 major and 2 minor

also need evidence of preceding streptococcal infection

Question 7

Most common symptom of rheumatic fever

Answer 7

arthritis

• most people get this
• polyarthritis - pain can move between the joints

Question 8

Sydenhams chorea

Answer 8

symptoms of dancing but uncontrollable
and slightly hypotonic
-can also become more emotional

Question 9

Erythema marginatum

Answer 9

-rashes, uncommon
on upper arms, legs and not face
-spreads outwards in a circular shpae
-edge become raised, red and center clearas

Question 10

How does rheumatic fever cause this

Answer 10

get a normal host response to group A streptococcus - produce antibodies to bacterial antigens
-then get production of cross-reactive antibodies giving an immune response against the pathogen, but produces antibodies which are recognised by the host and microbial antigens (host cells - cardiac, neural, joints)

• these antibodies cross react with collagen and cardiac valvular endothelia antigens and t cells infiltrate leading to inflammation or long term damage (caridits then RHD)
• autoantibody mediated neuronal cell signaling in cerebrospinal fluid may be part of pathogenesis in chorea

-can get bad scaring of heart valves with repeated rhematic fever attacks

(cause a reaction against the streptococcus , and then this will go to other places and cause an autoimmune reaction)

Question 11

Symptoms and signs

Answer 11

Prolonged PR interval
stretococcal titers - were elvated above nromal range
-troat normal examination and negative culture
-echo showed aortic regugitation

Question 12

Streptococcal antibody titers

Answer 12

most rheumatic fever cases do not have culture positive throat or history of sore throat either

• even when group A strep cultured, could be represent carriage, does not confirm recent infection
• tests used - tests are plasma ASO and anti-Dnase B

Question 13

Treatment

Answer 13

Penicillin is used to treat this

-can have aqueous, or can have intramuscular injection - to prevent in children which known areas

Question 14

Septic arthritis vs acute rhuematic fever

Answer 14

Any age group – infancy through to young childhood (peak age < 10 yrs)
• Acute active infection- arthritis due to bacteria and pus in the joint – pyogenic bacteria (S.aureus and S.pyogenes)
• Treatment with cleaning joint and penicillin to clear infection

Rhematic fever
School age 5 – 15 year • Autoimmune antibody
response to S.pyogenes
• Multisystem inflammatory disease (symptoms and signs of heart, joint, skin, brain involvement
• Penicillin used long term to prevent recurrence (secondary prevention)