Lecture 18 - Septic arthritis and Rheumatic fever Flashcards Preview

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Flashcards in Lecture 18 - Septic arthritis and Rheumatic fever Deck (14):

Group A Streptococcal disease

-skin - empetigo, cellulitis
-scarlet fever
-bloodstream infection
-septic arthritis
-necrotising fascitis
-toxi shock syndrome
-puerperal sepsis

-can have delayed sequalae following uncomplicated infections
-can cause acute rheumatic fever, rhuematic heart disease or streptococcla glomerulonephritis


Septic arthritis

-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


what is most common cause of joint infection

-staphylococcus aureus
2nd most common cause Streptococcus pyogenes


Main points about septic arthritis

-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


Rhematic fever

-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


Major and minor criteria for rheumatic fever

Need 2 major or 1 major and 2 minor

also need evidence of preceding streptococcal infection


Most common symptom of rheumatic fever

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


Sydenhams chorea

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


Erythema marginatum

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


How does rheumatic fever cause this

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)


Symptoms and signs

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


Streptococcal antibody titers

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



Penicillin is used to treat this
-can have aqueous, or can have intramuscular injection - to prevent in children which known areas


Septic arthritis vs acute rhuematic fever

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)