Cardiac Infections + Microbiology Revision Flashcards
what is bacteraemia
presence of bacteria in the bloodstream
is blood usually sterile
yes
what could happen if bacteraemia is not treated
patient could go into septic shock and die
why is it important to have sterile techniques when taken blood cultures
to avoid contamination and false negatives
what is the difference between a positive and negative blood culture bottle
different colours, positive infected with organism
what should you not start antibiotics without
evidence of bacterial infection
what is infective endocarditis
infection of the endothelium of the heart valves
what are the types of onsets of infective endocarditis
acute or subacute
what are the predisposing factors of IE
heart valve abnormality, prosthetic heart valve, intravenous drug users, patients with IV lines
what are three types of heart valve abnormalities and why do they predispose IE
calcification/ sclerosis in elderly,
congenital heart disease,
post rheumatic fever
creates turbulent blood flow which causes endothelial injury, inflammation, bacteria adhere to inflamed sites
why does a prosthetic valve predispose a patient to IE
as bio films grow over them
describe the pathogenesis of endocarditis
heart valve damaged- turbulent blood flow over roughened endothelium- platelets/ fibrin deposited, bacteraemia (may be transient e.g. from dental work)- organisms settle in fibrin/ platelet thrombi becoming a microbial vegetation
which side of the heart is most likely affected with IE
left side of heart- mitral and aortic valves
why do infected vegetations pose such a risk
as they are friable and easily break off, can lodge in next capillary bed causing abscesses or haemorrhage
what can dislodges infected vegetations cause if they travel distally
gangrene/ septic emboli
what are the most common causative agents of IE, commonest first
staphylococcus aureus,
viridans streptococci,
enterococcus sp,
staph epidermidis
what atypical organisms can cause endocarditis
bartonella, coxiella burnetii (Q-fever) (in farm animal poo), chlamydia, legionella, mycoplasma, brucella
how are atypical organisms detected
cant be grown on blood culture but detected via serology- looking for antibodies
what gram negative organisms can cause endocarditis and how are the detected
HACEK organisms and non HACEK organisms
HACEK= can be detected in blood cultures but need to be help for 7-10 days
(HACEK; Haemophilus spp., cardiobacterium etc)
along with atypical and gram negatives, what other unusual organism can cause IE
fungi
what are the major criteria in dukes criteria for diagnosis endocaritis
two separate pos blood cultures with microorganisms typical for IE
echocardiographic evidence of endocardial involvement
typical valvular lesions: vegetations, abscess or surgical wound rupture of a prosthetic valve
new valvular regurgitation
what organisms are typical for IE
staphylococcus aureus, viridans streptococci, community acquired enterococci, streptococci bovis, HACEK group
what are the minor criteria of duke criteria
predisposition, temp >38, vascular or immunological phenomena, micro-bacterial evidence
what non immunological investigations are done to diagnose IE
transthoracic echocardiography and (not always necessary) transoesophageal echocardiography
gram positive cocci in clusters=
staph
gram pos cocci in chains =
strep
what antibiotics for staph infections
penicillins
what are lancefield group a antigens
molecules on surface of strep
describe the coagulase test
used to differentiate Staphylococcus aureus (positive) from Coagulase Negative Staphylococcus (CONS).
identifies whether an organism produces the exoenzyme coagulase, which causes the fibrin of blood plasma to clot
Staphylococcus aureus produces free coagulase; Staphylococcus epidermidis does not.
what is the most common coagulase negative staphylococcus
staphylococcus epidermidis
what is the usual habitat of staph epidermidis
often a skin contaminant but can infect prosthetic material
what does staph aureus look like
gram pos, in clumps, golden on blood agar (beta haemolysis)
what are the three types of haemolysis
alpha- green discolouration surrounding colony= partial decomposition of haemoglobin
beta- complete break down, clearing of agar around the colony
gamma- no breakdown, brownish discolouration
what other mechanisms can be used to identify microorganisms
mass spectrometer (peptides, amplification of DNA), agar culture, serology, PCR
what should be done if a patient has a positive result for staph aureus in the blood
if possible remove IV device, think if there is an IV source, asses severity and source before giving antibiotics
what are the presenting symptoms of acute endocarditis
overwhelming sepsis and cardiac failure
what are the symptoms of subacute endocarditis
fever, malaise, weight loss, tiredness, breathlessness
what are the clinical signs of subacute endocarditis
fever, new/changing heart murmur, finger clubbing, splinter haemorrhages, splenomegaly, roth spots, osler nodes, janeway lesions, microscopic haematuria
what are roth spots
retinal haemorrhages with white or red centres
what are janeway lesions
non-tender, small erythematous or haemorrhagic macular or nodular lesions on the palms or soles
what are osler nodes
painful, red, raised lesions found on the hands and feet (osler ouch)
what type of haemolysis does strep viridans cause
alpha
what type of endocarditis does strep viridans cause
subacute
where are strep viridans found
normal oral commensals
are there lacefield group on viridans
no
why is it important to take 3 sets of blood cultures
to determine between a causative agent and a contaminant
why are infections caused by atypical organisms harder to treat
as harder to identify causative organism and tailor antibiotics
which is the first echocardiography to be performed
transthoracic
when should a transoesophageal echocardiography be performed
- prosthetic valve or intracardiac device
- positive for infective endocarditis
- non-diagnostic images
- negative for IE but high clinical suspicion
when does the infection in early prosthetic valve endocarditis usually occur
at time of valve insertion (until following 60 days)
what is usually the causative agent in early prosthetic valve endocarditis
staph aureus or epidermidis
when does late prosthetic valve endocarditis occur and due to what
up to many years after valve insertion, due to co-incidental bacteraemia
what should all patients with prosthetic valves be given
vancomycin + gentamycin+ (later after other two have worked a bit) rifampicin
what are the complications of IE
cerebral emboli, roth spots, haemorrhages, murmurs, conduction disorders, cardiac failure, systemic emboli, loss of pulses, clubbing, splinter haemorrhages, janeway lesions, oslers nodes, splenomegaly, hematuria
what part of heart is most commonly affected by IE in PWIDs
right side- tricuspid valve
what organism is common in IE in PWIDs
staph aureus
how is native valve endocarditis treated and what is it called by
viridans strep
amoxicillin and gentamicin (IV)
what happens when amoxicillin and gentamicin are used together
synergistic effect
how is prosthetic valve endocarditis treated
Vancomycin & gentamicin IV
Add in day 3 to 5 (delayed) rifampicin PO
valve replacement often required
what ids rifampicin good at getting rid of
biofilm
how is drug user endocarditis treated (MSSA)
flucloxacillin IV
what is staph aureus IE treated (not MSSA)
flucloxacillin IV
how is viridans streptococci IE treated
Benzylpenicillin iv & gentamicin iv (synergistic)
how is enterococcus sp. treated
Amoxicillin/ vancomycin & gentamicin IV
how is staph epidermidis treated
Vancomycin & gentamicin IV & rifampicin PO
describe the monitoring of treatment in IE and how long it usually lasts
IV antibiotics for 4-6 weeks
monitor cardiac function, temperature, serum -reactive protein
if failing consider surgery
what worsen the prognosis of IE
patient characteristics: age, prosthetic valve, diabetes mellitus, co-morbidity
clinical complications of IE: heart failure, renal failure, ischaemic stroke, brain haemorrhage, septic shock
microorganism: staph aureus, fungi, non HACEK gram neg bacilli (bad ones)
echocardiographic findings: pulmonary hypertension, severe valve dysfunction, large vegetations, low LV ejection factor,
when in IE should urgent surgery be taken out in stead of medical management
severe heart failure (and HF with severe vale regurgitation), high embolic risk with other poor prognostic values, persistent sepsis
when in IE can elective surgery be taken out in stead of medical management
HF with severe vale regurgitation, high embolic risk with no nother prognostic values,
in what group of people is myocarditis common and what does it result in
in young people (cause of sudden death)
what are the symptoms of myocarditis
fever, chest pain, shortness of breath, palpitations
what are the signs of myocarditis
arrhythmia, cardiac failure
what is myocarditis
inflammation of the cardiac muscle
what is myocarditis mainly caused by
enteroviruses- Coxsackie A and B, echovirus
how is myocarditis diagnosed
viral PCR- throat swab and stool for enteroviruses, throat swab for influenza
what else can cause myocarditis
non infectious agents (toxins, hypersensitivity, immunological syndromes)
infectious aetiologies (viruses, parasites, bacteria, fungal, protozones)
what causes the inflammation of the myocardium in myocarditis
the body’s immune response (innate and acquired)
what is pericarditis
inflammation of the pericarditis
what is the main feature of pericarditis
chest pain- often when breathing
what are the common causes of pericarditis
viruses, bacteria (less common), mycoplasma, fungal, parasitic
(post cardiothoracic surgery, rarely secondary spread from endocarditis or pneumonia)
non infectious (neoplasm, idiopathic, MI, hyperthyroidism)
drug induced
trauma related
what is the treatment for pericarditis
antibiotics and drainage
what is night sweats a key word for
TB
what organism causes Q fever
coxiella burnetti
what is coagulase
a bacterial enzyme which brings about the coagulation of blood or plasma and is produced by disease-causing forms of staphylococcus
