Flashcards in Cardiac Infections Deck (58):
What can give us false negatives when taking blood and looking for bacteria?
Recent antibiotics usage, they can still kill existing bacteria even in the blood sample.
Can be contaminated by skin organisms.
What are gram positive cocci in clusters?
What three questions should we ask when going to speak to a microbiologist?
Is the organism likely to be a skin contaminant?
If not, where in the patient is it coming from.
Does the patient need antibiotics and if so which ones.
If we find streptococcus pneumonia in the blood where is the infection likely to be coming from?
Pneumonia and meningitis.
If we find e.coli, klebsiella or other coliforms in the blood where is the infection likely to be coming from?
Urinary tract or gut infection.
If we find staphylococcus aureus in the blood where is the infection likely to be coming from?
Skin or wound infection. Bone/joint infection or endocarditis.
What are two common skin contaminants found in blood samples?
Staphylococcus epidermidis and corynebacterium sp (diphtheroids).
What is staphylococcus and what can it commonly effect?
Commonest coagulase negative staphylococcus. Often a skin contaminant.
Can infect prosthetic materials e.g. IV lines, prosthetic heart valves and joints.
How can we try and stop skin contaminants getting into samples?
Taking more than one sample from different areas.
What is infective endocarditis? What are the two types?
Infection of the endothelium of the heart valves.
Can be life threatening as it is often diagnosed late.
Has up to a 25% mortality rate.
May be acute or subacute.
How many people does infective endocarditis effect?
What is the mean age?
Why are hospital acquired cases increasing?
Approx. 1 in 1000.
Due to staphylococcus aureus.
What four factors can predispose to infective endocarditis?
Heart valve abnormalities.
Prosthetic heart valves.
What heart valve abnormalities can predispose to infective endocarditis?
Calcification/sclerosis in the elderly.
Congenital heart disease.
Post rheumatic fever.
Any valvular disease e.g. Mitral.
What is the pathogenesis of endocarditis?
Heart valve damaged causing turbulent flow over rough endothelium.
Platelets and fibrin deposited.
Bacteraemia e.g. From dental work.
Organisms settle in fibrin/platelet thrombi becoming a microbial vegetation.
Infected vegetations become friable and break off. Lodge in capillary bed causing abscess or haemorrhage.
What population of patients are vegetations more common in?
What side of the heart is more commonly affected by endocarditis?
Left side. Mitral and aortic valves.
What organisms commonly cause endocarditis on native heart valves? Put them in order of frequency highest first.
Viridans streptococci (nearly as common as aureus - most common according to Oxford book).
Last two not far apart but far less frequent than the first two.
What atypical organisms can cause endocarditis?
Bartonella, coxiella burnetii, chlamydia, legionella, mycoplasma, brucella. Gram negatives and fungi.
What can coxiella burnetii cause and how do we catch it?
Q fever. Get it from breathing in contaminated animal dust.
What are the presenting symptoms of acute endocarditis? Why do we normally get it?
Overwhelming sepsis and cardiac failure. Usually due to virulent (aggressive) organisms such as staph aureus.
What symptoms do we get with subacute endocarditis?
Fever, malaise, weight loss, tiredness and breathlessness.
What signs do we get with subacute endocarditis?
Fever, new or changing heart murmur, finger clubbing, splinter haemorrhages, splenomegaly, Roth spots, janeway lesions, Osler nodes and microscopic haematuria.
What do Roth spots look like?
Retinal haemorrhages with white or pale centres.
What do Janeway lesions look like?
Non-tender, small erythematous or haemorrhagic macular or nodular lesions on the palms or soles only a few mm in diameter.
What do Osler nodes look like?
Painful red raised lesions found on the hands and feet.
How do we diagnose infective endocarditis?
Take 3 sets of bloods from different areas at different times. Before any antibiotics given. Usually first two are good enough for a diagnosis.
All positive - good indication of continuing bacteraemia.
One set positive or only one takes, may just be a contaminant.
Echocardiogram to look for vegetations on the valves.
What gives us a better clinical outcome for infective endocarditis?
When we identify the causative organism.
If blood cultures are negative but we are sure there is infection what else can we do?
Serology for atypical organisms, but we are more likely to start with an echo.
What two types of prosthetic valve endocarditis do we get?
Early - within 60 days.
Late - up to many years later.
What is early prosthetic valve endocarditis often due to?
Staphylococcus epidermidis or staphylococcus aureus. Usually infected at the time of insertion.
What is late prosthetic valve endocarditis often due to?
Co-incidental bacteraemia. Wide range of possible organisms.
What are the features of endocarditis that we see in IVDU's?
Usually right sided - tricuspid valve.
Usually due to staphylococcus aureus.
Often presents as staph aureus pneumonia.
May not require valve replacement but long term prognosis poor.
What should we assume if there is a fever and a new murmur?
Endocarditis until proven otherwise.
What should we do for at risk people who have had a fever over a week?
What percentage of endocarditis can happen in normal valves?
Up to 50%
What presentation do we normally see with endocarditis of normal valves?
Usually acute coarse. E.g. Sepsis.
What presentation do we normally see with endocarditis of abnormal valves?
Follow a subacute coarse.
What are the 5 gram negatives that rarely cause endocarditis?
What is the empirical treatment for the different types of infective endocarditis?
Native valve - amoxicillin and gentamicin IV.
Prosthetic - vancomycin and gent IV and rifampicin PO.
IVDU - flucloxacillin IV.
What is the treatment for staphylococcus aureus endocarditis?
Flucoxacillin IV (+gent).
What is the treatment for MRSA endocarditis?
Vancomycin IV and rifampicin PO (+gent).
What is the treatment for Viridans streptococci endocarditis?
Benzylpenicillin and gent IV.
What is the treatment for enterococcus sp. endocarditis?
Amoxicillin/vancomycin and gent IV.
What is the treatment for staphylococcus epidermidis endocarditis?
Vancomycin and gent IV plus rifampicin PO.
How do we monitor patients during and after treatment?
Cardiac function, temp, serum CRP. If failing on antibiotic therapy, consider referral for surgery early.
What steps do we take to prevent endocarditis?
Patients with heart valve lesions, congenital heart defects or prosthetic heart valves are at risk. They get prophylactic antibiotics when having GI or GU procedures if infection suspected.
What is myocarditis?
Inflammation of heart muscle, more common in young people.
What are the symptoms of myocarditis?
Fever, chest pain, SOB and palpitations.
What are the signs of myocarditis?
Arrhythmias and cardiac failure.
What usually causes myocarditis?
Enteroviruses mainly but other viruses on occasion.
How do we diagnose myocarditis?
Viral PCR. throat swab and stool for enteroviruses. Throat swab for flu.
What is pericarditis?
Inflammation of the pericardium, often accompanied by myocarditis.
What is the main symptom feature of pericarditis?
Chest pain relieved by sitting forward.
How do we treat myocarditis?
What causes pericarditis?
Mainly viral. Can be bacterial, after cardiac surgery for example. Very rarely we have a secondary spread from endocarditis from pneumonia.
How do we treat pericarditis?
Supportive treatment, unless bacterial and then we need antibiotics and drainage.
What can infective endocarditis lead to?
Valvular insufficiency, myocardial and other abscesses, congestive heart failure and death. Stroke and organ damage from thrombi.