infective endocarditis and other infections Flashcards
blood cultures
normally sterile
the presence of bacteria in the bloodstream = bacteraemia
may develop sepsis shock and die if not treated
>blood cultures the most important test for diagnosis
>collection of blood culture:
avoid contamination
collect 2 sets at separate sites
volume is the most important factor
timing of collection -
interpretations of blood culture
common contaminants ie stuff that lives on the skin
causes of false negative blood cultures
multiple BC+ from separate sites
>too little volume collected, antimicrobials prior to collection, fastidious organism that does not grow in standard blood cultures
diagnosis of bacteraemia
examination > sampling > transport preparation >loading > gram staining > sub-culturing > organism ID and AST > validation > report
all this within 24 hours
bacteraemia - think !
> can be subdivided into continuous (?) and intermittent (ie an abscess)
what is the usual habitat of the organism ?
what disease is this organism associated with ?
what is the optimum antimicrobial management required ?
what do we need to avoid w/o microbiological sample
empiric antibiotics
infective endocarditis
infection of the endothelium of the heart valves
life threatening
>often diagnosed late (will be mistaken for something else)
usually left side or heart affected (mitral and aortic valves)
may be acute or subacute
categorisations of endocarditis :
R vs L
native vs prosthetic valve
acute vs subacute
and according to the microorganism
pathogenesis
> heart valve damage
turbulent blood flow over roughened endothelium
platelets / fibrin deposited
bacteraemia eg from dental treatment
organisms settle in fibrin / platelet thrombi becoming a microbial vegetation
1. valvular destruction
2. microvascular and large vessel embolisation
3. metastatic inception of target organisms
4. immunologic phenomena (ie hypocomplementemic glomerulonephritis and false positive serologic findings)
predisposing factors
> heart valve abnormality ie calcification / sclerosis / congenital heart disease /
post rheumatic fever
> poor dentition IV drug ise haemodialysis chronic liver disease diabetets neoplastic disease indwelling IVDs
what causes endocarditis
mostly gram + bacterias ie Staphylococcus / strep
uncommon = legionella , mycoplasma , chlamydia etc (+)
(-) = HACEK organisms and fungi lol
s aureus ! s viridans ! s gallolyticus ! HACEK these ^ are the main ones
diagnosis - the modified duke criteria
rooted in microbiologic, echocardiographic and clinical factors
has lower sensitivity in infections
major = typical micro-organisms >persistently positive blood cultures
>single positive blood cultures
»vegetation
» new valvular regurgitation
minor = positive blood cultures
predisposing cardiac conditions or IV drug use
vascular phenomena
immunologic phenomena
staph . epidermis
often a skin contaminant but can infect prosthetic material
>take more than one set of blood cultures
presentation of endocarditis
overwhelming sepsis and cardiac failure
subacte presentation
fever malaise weight loss tiredness breathlessness
signs = fever new or changing heart murmur
finger clubbing splinter haemorrhage
splenomegaly
roth spots , osler nodes, janeway lesions , microscopic haematuria
TTE/TOE
transthoracic echocardiogram
can use for diagnosis of endocarditis
prosthetic valve endocarditis
can get early and late presentations
early = usually infected at time of valve
late =
