Case 35: An Aboriginal Boy Flashcards
What is the Gram morphology for Strep. pyogenes?
Gram +ve cocci in chains
What is the colony morphology for Strep. pyogenes on HBA?
Large colonies - beta haemolytic
What are the catalase results for Strep. pyogenes?
Catalase negative
What is the colony morphology for Staph. aureus on HBA?
Cream pigmented - beta haemolytic
What is the Gram morphology for Staph. aureus?
Gram +ve cocci in clusters
What are the catalase and coagulase results for Staph. aureus?
Catalase and coagulase positive
What does the ASOT test investigate?
If there is any antibody against streptococcus
What is impetigo?
A contagious bacterial skin infection forming pustules and yellow crusty sores caused by strep. pyogenes or staph. aureus
This patient, as well a impetigo, also had a severely painful swollen right knee and ankle and pansystolic murmurs loudest at the apex with an elevated cell count. What other condition is likely to be present? Why?
Rheumatic fever
Addition of arthralgia + fever + carditis is associated with Rheumatic fever. M-protein immune response cross-reacts to myocardium.
What is the likely sequence of events that lead from impetigo to rheumatic fever?
Skin infection with strep. pyogenes → immune response to M-antigen → attach M-antigen-like molecules in joints and heart
What is rheumatic fever following impetigo a marker of?
Poverty and overcrowding
What other complications of infection with strep. pyogenes and staph. aureus could ocur?
Toxic shock - both produce superantigens
What is the likely source of infection by strep. pyogenes?
Respiratory tract/mouth
What is the likely source of infection by staph. aureus?
Skin
What treatment should be given for impetigo and rheumatic fever?
Wash skin and oral antibiotic
