Microbiology 1- Endocarditis and other cardiac infections Flashcards
What 2 symptoms together are endocarditis until proven otherwise?
Fever + new murmur
What is the main cause of infection on a normal valve?
Staph aureus
Does endocarditis on a normal valve tend to run an acute or subacute course?
Acute
Does endocarditis on an abnormal valve tend to run an act or subacute course?
Subacute
What are the common types of bacteria that cause native valve endocarditis? (4)
Staph aureusViridans streptococciEnterococcusStaph. epidermidis
What is the difference between bacteraemia and septicaemia?
Bacteraemia = presence of bacteria in the bloodSepcticaemia = multiplication of bacteria in the blood
How is bacteraemia/ septicaemia tested for?
Blood samples are taken and put in blood culture machines - this incubates the bottles at 37 degrees and detects the production of CO2 indicating growthIf CO2 is detected, the bottle is promptly removed and a small sample cultured and looked at under the microscope
What does the presence of bacteria in the blood usually indicate?
That there is a focus of infection elsewhere in the body (can be a skin contaminant)
What is infective endocarditis?
Infection of the endothelium of the heart valves
What are the categories of endocarditis based on time of onset?
AcuteSubacute (over weeks/ months)
What is the mean age of getting infective endocarditis?
Majority greater than 50 years old but can occur in children with congenital heart disease
Predisposing factors for endocarditis?
Heart valve abnormality e.g. calcification/ sclerosis in elderly, congenital heart disease, post rheumatic feverProsthetic heart valveiv drug usersIntravascular lines
How does endocarditis form?
Heart valve damage causes turbulent blood flow over roughened endotheliumPlatlets and fibrin are depositedBacteraemia occurs (may be very transient)Organisms settle in fibrin/ platelet thrombi becoming a microbial vegetationInfected vegetations are friable and break off becoming lodged in the next capillary bed they encounter causing abscesses or haemorrhage (can be fatal)
What side of the heart is usually affected by endocarditis?
Left side (mitral and aortic valves)
What are the unusual organisms causing endocarditis?
Atypical organisms (Bartonella, Coxiella burnetti, Chlamydia, Legionella, Mycoplasma, Brucella)Gram negativesFungi
What microorganism causes Q fever?
Coxiella burnetti
What are the usual presenting symptoms of acute endocarditis?
Overwhelming sepsisCardiac failure
Symptoms of subacute endocarditis?
FeverMalaiseWeight lossTirednessBreathlessness
Signs of subacute endocarditis?
FeverNew or changing heart murmurFinger clubbingSplinter haemorrhagesSplenomegalyRoth spots, Janeway lesions, Osler nodesMicroscopic haematuria
What are Janeway lesions?
non-tender, small erythematous or haemorrhagic macular or nodular lesions on the palms or soles
Roth spots?
A hemorrhage in the retina with a white center.
What are osler nodes?
painful, red, raised lesions found on the hands and feet
Diagnosis of endocarditis?
Take 3 sets of blood cultures (taken at different times at different sites before antibiotics are started)If blood culture negative, consider serology for atypical organismsEchocardiogram (transoesophageal more sensitive than transthoracic)
What are the 2 different types of prosthetic valve endocarditis and what usually causes each?
Early (within 60 days of placement) = usually infected at time of valve insertion = staph aureus or staph epidermisLate = many years later valve insertion due to co-incidental bacteraemiaWide range of possible organisms
