4- infective endocarditis and other cardiac conditions Flashcards
what are bacteraemias?
viable bacteria that is found in blood (blood is supposed to be sterile)
are all bacteraemias clinically significant?
no - some can just be because skin hasn’t been adequately cleansed or because technique isn’t good
bacteraemia that cause endocarditis for example need 6 weeks antibiotics - some bacteraemia need no treatment
what is important in blood culture collection?
has to be very good technique and very sterile to make sure that results are correct
what happens with the blood after blood culture?
blood cultures go off to lab and into automated machine and colour change indicates positive blood culture. from that the lab will take sample and try grow bug and do molecular tests to find the name of the molecular bug, this involves a gram stain. usually takes about 2 days to get results
why is it important to know what sites bugs infect at?
different bugs like to cause infection at different sites (the significance of positive culture depends on whether you expect that bug to cause disease at that site)
- if bug relevant to site, you then decide what antibiotic is best
why it important to take right amount of blood for blood culture?
if too little you may miss the infection
= you want many blood cultures positive with same bug
if 1 positive and rest negative more likely to be contaminant
if all positive then more likely to be bug
what is endocarditis?
infection of inner lining of muscles - continuous with lining of blood vessels
life threatening (up to 25% mortality)
what does acute & subacute endocarditis mean?
acute = aggressive or virulent
subacute = slow onset (easy to miss)
what does endocarditis look like on echocardiogram?
looks like cauliflowers on valves
what are predisposing factors for endocarditis?
- heart valve abnormality = calcification/sclerosis in elderly, congenital heart disease, post rheumatic fever (more likely to have abnormal valve)
- Prosthetic heart valve
- People who inject drugs (you’re acting endothelium a lot)
- Intravascular lines (like people on dialysis who have lines)
what is transient bacteraemia and when can it be damaging?
have no consequence normally but if foreign things in body then they can see bacteria
what is pathogenesis of infective endocarditis? (things you need)
- damaged valve
- turbulent blood flow & roughened endothelium
- platelets/fibrin deposited
- bacteraemia (may be very transient) e.g. from dental treatment in high risk patients
- organisms settle in fibrin/platelet thrombi becoming a microbial vegetation
how does infected vegetations cause problems in different areas?
they are friable and break off and then lodge into next capillary bed
if infective endocarditis in right side of heart that becomes friable and breaks off, where most commonly will it cause problems?
kidneys and brain etc
if infective endocarditis in right side of heart that becomes friable and breaks off, where most commonly will it cause problems?
in lung bed - causing lots of septic pulmonary emboli
what are the most important organisms for infective endocarditis
- Staph aureus = 38% (more virulent and more likely to affect native bugs)
- viridans group streptococci = 31%
- enterococcus sp = 8%
- staphylococcus epidermis = 6% (more likely when prosthetic valve, not as virulent as staph aureus)
how many sets of blood culture should you take? and why?
Take 3 sets of blood cultures -very important since if all are positive there is good evidence of continuing bacteraemia. If only one set taken and is positive might be a contaminant. Better clinical outcome when causative organism is identified
each set has 2 bloods
should antibiotics be given before or after blood cultures?
blood cultures always before - antibiotics after
what should you do if blood culture negatives?
consider serology for atypical organisms (in people that really sound like symptoms for infective endocarditis)
what are atypical organisms?
bugs that cause culture negative endocarditis
what are some examples of atypical unusual organisms that can cause infective endocarditis?
coxiella burnetii (Q fever) = farm animals is classic exposure (IMPORTANT ONE)
also can be bartonella, chlamydia, legionella, mycoplasma, brucella, gram negative HACEK organisms and funghi (usually in immunosuppressed people and very difficult to treat)
what is reason for blood cultures?
to identify the bug to then put patient on most efficient antibiotic for that particular bug
what is Duke’s criteria?
criteria to try and decide if patient has endocarditis (as can be very tricky)
major criteria = 2 separate +ve blood culture, echo with evidence, new valvular regurgitation
minor criteria = - predisposing heart condition, temp greater than 38, vascular phenomena, immunological phenomena, microbiological evidence
*don’t worry about it too much
how to diagnose Q fever? (culture negative)
blood test to check if right ratio of antibodies
what is important systematic approach to diagnosing infective endocarditis?
- need right history
- right blood culture
- right imaging
generally how quickly does each bacteria onset?
staph aureus = quick onset, a couple of days
viridans strep = happens much more slowly, over a couple of weeks
what is a hint to staph epidermidis endocarditis?
in someone with prosthetic valve
what test distinguishes between staphylococcus?
coagulase test
coagulase +ve = staph aureus
coagulase -ve = staph epidermidis
what gram and shape is
a) staphylococcus?
b) streptococcus?
a) gram +ve and clusters
b) gram +ve and chains
what is MALDI-TOF?
Matrix Assisted Laser Desorption/Ionisation – Time Of Flight
= Rapid organism identification & Rapid susceptibility
what is most common coagulase negative staphylococcus?
staphylococcus epidermidis
where does staph epidermidis infect?
often a skin contaminant BUT can infect prosthetic material e.g. ICED, prosthetic heart valves/joints, lines
what are skin contaminants bugs?
staph epidermidis (important) and corynebacterium sp (diphtheroids), a rod
when in process is maldi tof done?
usually done after culture
how much antibiotic required for infective endocarditis?
at least 6 weeks
does staph aureus spread?
yes - very commonly spreads and can go anywhere, seed wherever it can (commonly at places if septic arthritis, IV device etc)
*this means that if staph aureus endocarditis then you should check all other places it can be
what is clinical subacute history?
- slow onset
- fever
- malaise
- weight loss
- tiredness
- breathlessness
- Fever
- New or changing heart murmur
- finger clubbing
- splinter haemorrhages
- splenomegaly
- Roth spots, Janeway lesions, Osler nodes
- microscopic haematuria
*very general presentation (could be lots of things)
what is acute clinical history of endocarditis?
- presents as overwhelming sepsis & cardiac failure
- usually due to aggressive virulent organisms like staph auerus
how do you test between different streptococci?
put on blood agar and depending on behaviour (whether they produce toxin that lysis blood in agar classified to beta (complete breakdown), alpha (partial breakdown), gamma (no haemolysis)
what is most common haemolysis in endocarditis?
mostly alpha haemolytic = like strep viridans
what is most common type of bug of sub acute endocarditis?
streptococci
what are alpha haemolytic strep examples?
viridans strep group:
- Strep. mitis
- Strep. sanguinis
- Strep. mutans
- Strep. salivarius etc.
what are characteristics of sub acute endocarditis bugs?
- Normal oral commensals
- No Lancefield group or capsule
what is action plan if clinical suspicion of infective endocarditis?
transthoracic echocardiography and then most people have transesophageal echocardiography (to see much closer and can take better pics)
what is good and bad about transoesophageal echocardiogram (ECG)?
- closer to heart so takes better pics
- but does need to be sedated and much longer procedure
when early infection of prosthetic valve endocarditis - what is it usually due to?
early as in infected at time of valve insertion
usually due to:
staph epidermidis
staph aureus
when late infection of prosthetic valve endocarditis - what is it usually due to?
late = many years after valve insertion
due to:
- coincidental bacteraemia (wide range)
what are common antibiotics prescribed for prosthetic valve endocarditis?
vancomycin, gentamicin, rifampin
what can occur as result of prosthetic valve endocarditis?
- splinter hemorrhage
- clubbing
- oslers nodes
- splenomegaly (only if for a long time)
- cerebral emboli
- cardiac murmurs
- systemic emboli
- loss of pluses in limbs
what is usual drug for endocarditis in person who injects drugs?
- Usually Staphylococcus aureus
- Suspect in Staphylococcus aureus plus septic pulmonary emboli
*usually 75-93% have normal valves which shows how good staph aureus is
where do people who inject drugs most commonly get endocarditis?
right sided endocarditis = tricuspid - mitral - aortic
what antibiotics are prescribed for native valve endocarditis?
amoxicillin & gentamicin IV
(viridans strep)
what antibiotic is prescribed for endocarditis for people who inject drugs?
flucloxacillin IV
what antibiotic is prescribed for people with prosthetic valve endocarditis?
vancomycin & gentamicin IV
- add in day 3 to 5 rifampicin PO
(often valve replacement required)
what does amoxicillin not work for?
staph aureus
what is course of tests for suspected infective endocarditis?
blood culture then if positive identification by mass spec then if +ve do agar culture and if -ve do agar culture
*if blood culture negative to serologies in some cases
what antibiotic should be used for staph aureus endocarditis?
flucloxacillin IV (only if MMSSA - doesn’t work if MRSA)
if MRSA = same as for prosthetic valves
what antibiotic for enterococcus sp?
amoxicillin and gentamicin IV
what antibiotics for viridans streptococci?
benzylpenicillin IV & gentamicin IV
what antibiotics for staphylococcus epidermidis?
vancomycin & gentamicin IV and rifampicin
what should you monitor in infective endocarditis?
monitor cardiac function with temp & serum CRP (c-reactive protein)
monitor clinical response
- consider referral to surgery early
what are the 4 categories of risk that help determine prognosis?
- patient characteristics e.g. age, diabetes
- clinical complications of IE e.g. heart failure, renal failure etc
- microorganisms e.g. type of organism
- echocardiographic findings e.g. valve stuff
is there outpatient antibiotics available?
yes - there is a system in place to determine
what bugs do you get with implantable devices?
- Staphylococcus aureus
- Staphylococcus epidermidis
- Corynebacterium sp.
- Propionibacterium acnes
(skin organisms)
what are risk factors for ICED infections? (implantable cardiac electronic devices)
- Pre procedure prophylaxis errors
- Complexity of procedure
- Temporary pacer use
- Type of device
- Number of revisions / reinterventions
- Fever within 24 hours
- Heart failure, renal failure
- Haematoma post procedure
what can be tricky about diagnosing ICED?
determining where infection is, it can just be in like knees etc - can use Duke criteria to help diagnose
what is myocarditis symptoms?
fever, chest pain, shortness of breath, palpitations
what is myocarditis signs?
arrhythmia, cardiac failure
what is myocarditis caused by?
Mainly caused by enteroviruses -Coxsackie A & B, echovirus, but other viruses possible the list is extensive.
= More common in young people (cause of sudden death)
how is myocarditis diagnosed?
by viral PCR. Throat swab and stool for enteroviruses. Throat swab for influenza
what is pericarditis?
- Often occurs with myocarditis
- Chest pain main feature
mostly viral aetiology
when does pericarditis mostly occur?
post cardiothoracic surgery, rarely secondary spread from endocarditis or pneumonia treatment : antibiotics & drainage
