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Cardiovascular > Cardiac Infections + Microbiology Revision > Flashcards

Cardiac Infections + Microbiology Revision Flashcards

1
Q

what is bacteraemia

A

presence of bacteria in the bloodstream

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2
Q

is blood usually sterile

A

yes

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3
Q

what could happen if bacteraemia is not treated

A

patient could go into septic shock and die

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4
Q

why is it important to have sterile techniques when taken blood cultures

A

to avoid contamination and false negatives

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5
Q

what is the difference between a positive and negative blood culture bottle

A

different colours, positive infected with organism

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6
Q

what should you not start antibiotics without

A

evidence of bacterial infection

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7
Q

what is infective endocarditis

A

infection of the endothelium of the heart valves

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8
Q

what are the types of onsets of infective endocarditis

A

acute or subacute

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9
Q

what are the predisposing factors of IE

A

heart valve abnormality, prosthetic heart valve, intravenous drug users, patients with IV lines

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10
Q

what are three types of heart valve abnormalities and why do they predispose IE

A

calcification/ sclerosis in elderly,
congenital heart disease,
post rheumatic fever

creates turbulent blood flow which causes endothelial injury, inflammation, bacteria adhere to inflamed sites

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11
Q

why does a prosthetic valve predispose a patient to IE

A

as bio films grow over them

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12
Q

describe the pathogenesis of endocarditis

A

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

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13
Q

which side of the heart is most likely affected with IE

A

left side of heart- mitral and aortic valves

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14
Q

why do infected vegetations pose such a risk

A

as they are friable and easily break off, can lodge in next capillary bed causing abscesses or haemorrhage

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15
Q

what can dislodges infected vegetations cause if they travel distally

A

gangrene/ septic emboli

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16
Q

what are the most common causative agents of IE, commonest first

A

staphylococcus aureus,
viridans streptococci,
enterococcus sp,
staph epidermidis

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17
Q

what atypical organisms can cause endocarditis

A

bartonella, coxiella burnetii (Q-fever) (in farm animal poo), chlamydia, legionella, mycoplasma, brucella

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18
Q

how are atypical organisms detected

A

cant be grown on blood culture but detected via serology- looking for antibodies

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19
Q

what gram negative organisms can cause endocarditis and how are the detected

A

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)

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20
Q

along with atypical and gram negatives, what other unusual organism can cause IE

A

fungi

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21
Q

what are the major criteria in dukes criteria for diagnosis endocaritis

A

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

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22
Q

what organisms are typical for IE

A

staphylococcus aureus, viridans streptococci, community acquired enterococci, streptococci bovis, HACEK group

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23
Q

what are the minor criteria of duke criteria

A

predisposition, temp >38, vascular or immunological phenomena, micro-bacterial evidence

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24
Q

what non immunological investigations are done to diagnose IE

A

transthoracic echocardiography and (not always necessary) transoesophageal echocardiography

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25
Q

gram positive cocci in clusters=

A

staph

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26
Q

gram pos cocci in chains =

A

strep

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27
Q

what antibiotics for staph infections

A

penicillins

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28
Q

what are lancefield group a antigens

A

molecules on surface of strep

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29
Q

describe the coagulase test

A

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.

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30
Q

what is the most common coagulase negative staphylococcus

A

staphylococcus epidermidis

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31
Q

what is the usual habitat of staph epidermidis

A

often a skin contaminant but can infect prosthetic material

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32
Q

what does staph aureus look like

A

gram pos, in clumps, golden on blood agar (beta haemolysis)

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33
Q

what are the three types of haemolysis

A

alpha- green discolouration surrounding colony= partial decomposition of haemoglobin

beta- complete break down, clearing of agar around the colony

gamma- no breakdown, brownish discolouration

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34
Q

what other mechanisms can be used to identify microorganisms

A

mass spectrometer (peptides, amplification of DNA), agar culture, serology, PCR

35
Q

what should be done if a patient has a positive result for staph aureus in the blood

A

if possible remove IV device, think if there is an IV source, asses severity and source before giving antibiotics

36
Q

what are the presenting symptoms of acute endocarditis

A

overwhelming sepsis and cardiac failure

37
Q

what are the symptoms of subacute endocarditis

A

fever, malaise, weight loss, tiredness, breathlessness

38
Q

what are the clinical signs of subacute endocarditis

A

fever, new/changing heart murmur, finger clubbing, splinter haemorrhages, splenomegaly, roth spots, osler nodes, janeway lesions, microscopic haematuria

39
Q

what are roth spots

A

retinal haemorrhages with white or red centres

40
Q

what are janeway lesions

A

non-tender, small erythematous or haemorrhagic macular or nodular lesions on the palms or soles

41
Q

what are osler nodes

A

painful, red, raised lesions found on the hands and feet (osler ouch)

42
Q

what type of haemolysis does strep viridans cause

A

alpha

43
Q

what type of endocarditis does strep viridans cause

A

subacute

44
Q

where are strep viridans found

A

normal oral commensals

45
Q

are there lacefield group on viridans

A

no

46
Q

why is it important to take 3 sets of blood cultures

A

to determine between a causative agent and a contaminant

47
Q

why are infections caused by atypical organisms harder to treat

A

as harder to identify causative organism and tailor antibiotics

48
Q

which is the first echocardiography to be performed

A

transthoracic

49
Q

when should a transoesophageal echocardiography be performed

A
  • prosthetic valve or intracardiac device
  • positive for infective endocarditis
  • non-diagnostic images
  • negative for IE but high clinical suspicion
50
Q

when does the infection in early prosthetic valve endocarditis usually occur

A

at time of valve insertion (until following 60 days)

51
Q

what is usually the causative agent in early prosthetic valve endocarditis

A

staph aureus or epidermidis

52
Q

when does late prosthetic valve endocarditis occur and due to what

A

up to many years after valve insertion, due to co-incidental bacteraemia

53
Q

what should all patients with prosthetic valves be given

A

vancomycin + gentamycin+ (later after other two have worked a bit) rifampicin

54
Q

what are the complications of IE

A

cerebral emboli, roth spots, haemorrhages, murmurs, conduction disorders, cardiac failure, systemic emboli, loss of pulses, clubbing, splinter haemorrhages, janeway lesions, oslers nodes, splenomegaly, hematuria

55
Q

what part of heart is most commonly affected by IE in PWIDs

A

right side- tricuspid valve

56
Q

what organism is common in IE in PWIDs

A

staph aureus

57
Q

how is native valve endocarditis treated and what is it called by

A

viridans strep

amoxicillin and gentamicin (IV)

58
Q

what happens when amoxicillin and gentamicin are used together

A

synergistic effect

59
Q

how is prosthetic valve endocarditis treated

A

Vancomycin & gentamicin IV
Add in day 3 to 5 (delayed) rifampicin PO

valve replacement often required

60
Q

what ids rifampicin good at getting rid of

A

biofilm

61
Q

how is drug user endocarditis treated (MSSA)

A

flucloxacillin IV

62
Q

what is staph aureus IE treated (not MSSA)

A

flucloxacillin IV

63
Q

how is viridans streptococci IE treated

A

Benzylpenicillin iv & gentamicin iv (synergistic)

64
Q

how is enterococcus sp. treated

A

Amoxicillin/ vancomycin & gentamicin IV

65
Q

how is staph epidermidis treated

A

Vancomycin & gentamicin IV & rifampicin PO

66
Q

describe the monitoring of treatment in IE and how long it usually lasts

A

IV antibiotics for 4-6 weeks

monitor cardiac function, temperature, serum -reactive protein

if failing consider surgery

67
Q

what worsen the prognosis of IE

A

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,

68
Q

when in IE should urgent surgery be taken out in stead of medical management

A

severe heart failure (and HF with severe vale regurgitation), high embolic risk with other poor prognostic values, persistent sepsis

69
Q

when in IE can elective surgery be taken out in stead of medical management

A

HF with severe vale regurgitation, high embolic risk with no nother prognostic values,

70
Q

in what group of people is myocarditis common and what does it result in

A

in young people (cause of sudden death)

71
Q

what are the symptoms of myocarditis

A

fever, chest pain, shortness of breath, palpitations

72
Q

what are the signs of myocarditis

A

arrhythmia, cardiac failure

73
Q

what is myocarditis

A

inflammation of the cardiac muscle

74
Q

what is myocarditis mainly caused by

A

enteroviruses- Coxsackie A and B, echovirus

75
Q

how is myocarditis diagnosed

A

viral PCR- throat swab and stool for enteroviruses, throat swab for influenza

76
Q

what else can cause myocarditis

A

non infectious agents (toxins, hypersensitivity, immunological syndromes)

infectious aetiologies (viruses, parasites, bacteria, fungal, protozones)

77
Q

what causes the inflammation of the myocardium in myocarditis

A

the body’s immune response (innate and acquired)

78
Q

what is pericarditis

A

inflammation of the pericarditis

79
Q

what is the main feature of pericarditis

A

chest pain- often when breathing

80
Q

what are the common causes of pericarditis

A

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

81
Q

what is the treatment for pericarditis

A

antibiotics and drainage

82
Q

what is night sweats a key word for

A

TB

83
Q

what organism causes Q fever

A

coxiella burnetti

84
Q

what is coagulase

A

a bacterial enzyme which brings about the coagulation of blood or plasma and is produced by disease-causing forms of staphylococcus

Cardiovascular (34 decks)

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