Infective Endocarditis

Question 1

Risk factors for infective endocarditis?

Answer 1

Age > 60 years
Male sex
Intravenous drug use - predisposition to Staph. aureus infection and right-sided valve disease e.g. tricuspid endocarditis
Poor dentition and dental infections

Question 2

What is Infective endocarditis?

Answer 2

Infective endocarditis refers to any infection of the endocardial surface of the heart.
Infective endocarditis (IE) can be a life-threatening condition associated with a number of severe complications. It refers to infection of the inner lining of the heart known as the endocardium. Infection of the endocardium may involve one or more heart valves or an intracardiac device (e.g. prosthetic valve).

Question 3

The clinical presentation of IE is highly variable. There are two major disease courses:

Answer 3

Acute, rapidly progressive infection

Subacute, or chronic, low-grade infection

Question 4

There are three major types, or categories, of IE:

Answer 4

Native valve endocarditis (NVE): normal valves without previous intervention. May be acute or subacute.
Prosthetic valve endocarditis (PVE): may occur early (< 1 year) or late (> 1 year) following surgical intervention. Account for 10-20% of cases.
Intravenous drug abuse (IVDA) endocarditis: classically affects the tricuspid valve (50%). Staphylococcus aureus most common microorganism. (Right side)

Question 5

Intravenous drug abuse (IVDA) endocarditis: classically affects which valve? And what is the most common microorganism?

Answer 5

classically affects the tricuspid valve (50%). Staphylococcus aureus most common microorganism.

Question 6

Traditionally, IE was considered a fatal condition, which commonly occurred in patients with pre-existing valvular disease from … … disease. In the modern era, use of antibiotics has significantly improved outcomes.

Answer 6

Traditionally, IE was considered a fatal condition, which commonly occurred in patients with pre-existing valvular disease from rheumatic heart disease. In the modern era, use of antibiotics has significantly improved outcomes.

Question 7

It is estimated that over 50% of IE cases occur in patients aged > … years old. With the increasing number of invasive procedures and use of intracardiac devices, the incidence of IE is expected to rise. The use of devices has led to an increase in Staphylococcal IE, which is now the most common cause.

Answer 7

It is estimated that over 50% of IE cases occur in patients aged > 60 years old. With the increasing number of invasive procedures and use of intracardiac devices, the incidence of IE is expected to rise. The use of devices has led to an increase in Staphylococcal IE, which is now the most common cause.

Question 8

Patient-associated risk factors for IE

Answer 8

Age: more than half of IE cases occur in patients aged > 60 years old.
Male: sex predominance varies from 3:2 to 9:1.
Intravenous drug use: may occur due to contamination of drugs used for injection or seeding of skin flora during injection
Dentition: poor dental hygiene, dental infections and certain dental procedures increase risk.

Question 9

Cardiac risk factors for IE

Answer 9

Structural heart disease
Valvular heart disease: any valve pathology can predispose too IE.
Congenital heart disease (e.g. bicuspid aortic valve, ventricular septal defect and cyanotic heart disease).
Prosthetic heart valves: metallic, tissue and transcatheter devices all associated with IE
Previous IE: recurrence rate 2.5-9% across reports
Intravascular devices

Question 10

Other risk factors for IE?

Answer 10

Other risk factors

Immunosuppression (e.g. HIV)
Haemodialysis

Question 11

Streptococcal and … species are implicated in the majority of IE cases.

Answer 11

Streptococcal and staphylococcal species are implicated in the majority of IE cases.

Question 12

… and staphylococcal species are implicated in the majority of IE cases.

Answer 12

Streptococcal and staphylococcal species are implicated in the majority of IE cases.

Question 13

The most common cause of IE overall is …

Answer 13

The most common cause of IE overall is Staphylococcal aureus, which is the usual pathogen in IE associated with intravenous drug use (IVDU) and prosthetic heart valves. Other commonly isolated bacteria are Streptococcal and Enterococcal species, which used to be the most common cause of IE. They are typically associated with subacute IE.

Question 14

Causes of endocarditis can be divided into:

Answer 14

Native valve endocarditis (NVE)
Prosthetic valve endocarditis (PVE)
IVDU-associated endocarditis
Culture-negative endocarditis
Non-infective endocarditis

Question 15

NVE is commonly due to underlying rheumatic heart disease, congenital heart disease or structural heart disease. It is usually due to … species and presents with a subacute course.

Answer 15

Streptococcal species (alpha-haemolytic, S. bovis) and enterococci: implicated in around 70% of cases.
Staphylococcal species: implicated in around 25% of cases. More aggressive disease course.

Question 16

Prosthetic valve endocarditis

Answer 16

The aetiology of PVE depends on if it occurs early (< 1 year) or late (> 1 year). The time differentiation is an arbitrary cut-off. Some guidelines quote within 60 days as ‘early IE’. Coagulase-negative Staphylococcus (CoNS) account for 30% of PVE (most common).

Early PVE: occurring shortly after surgery. Staphylococcal species commonly implicated. Acute course that can cause local abscess, fistula formation, and valvular dehiscence.
Late PVE: occurring a medium-to-long period after surgery. Streptococcal species commonly implicated. Has a more subacute course.

Question 17

IVDU-associated IE

Answer 17

Due to injection through the venous system, IE affecting the right side of the heart is commonly seen with IVDU. Most common organism implicated is Staphylococcus aureus.

Question 18

Culture-negative IE

Defined as endocarditis with no definite microbiological aetiology despite adequate sampling. Culture negative IE may be due to:

Answer 18

Typical pathogens: usual bacterial pathogens may not be cultured in the lab because of early antibiotic use.
Pathogens with complex growth: some organisms are described as fastidious, with complex growth requirements in the lab
Intracellular bacteria: these bacteria cannot be cultured by standard methods
Non-bacterial pathogens (e.g. fungi)

Question 19

Rarely, endocarditis may occur in the absence of infection. Other terms for non-infective endocarditis include marantic endocarditis or Libman-Sacks endocarditis. It is due to sterile platelet thrombi on heart valves

Causes include:

…

Answer 19

Causes include:

Advanced malignancy (80%)
Systemic lupus erythematous
Other: Rheumatoid arthritis, burns

Question 20

A variety of pathogens can cause IE - The most common microorganisms that cause IE …. (3 species)

Answer 20

The most common microorganisms that cause IE are Staphylococcal, Streptococcal and Enterococcal species. As discussed, the microorganisms implicated in IE depends on the underlying cardiac disease (e.g. prosthetic or native valve) and patient factors (e.g. intravenous drug use).

Question 21

… …: causes both acute and subacute IE. May lead to significant valve destruction.

Answer 21

Staphylococcus aureus: causes both acute and subacute IE. May lead to significant valve destruction.

Question 22

Coagulase negative staphylococcus (CoNS): subacute course. Commonly associated with … devices.

Answer 22

Coagulase negative staphylococcus (CoNS): subacute course. Commonly associated with prosthetic devices.

Question 23

Alpha-haemolytic streptococci: commonly implicated in subacute IE due to poor …. Accounts for 50-60% of subacute IE cases. Examples include Viridans streptococci.

Answer 23

Alpha-haemolytic streptococci: commonly implicated in subacute IE due to poor dentition. Accounts for 50-60% of subacute IE cases. Examples include Viridans streptococci.

Question 24

Beta-haemolytic …
Group A: more virulent course, similar to S. Aureus.
Group B: usually an acute course. Typically seen in pregnancy.
Group D: streptococcus gallolyticus (previously streptococcus bovis) is a classic cause of subacute IE. It has a strong association with colorectal cancer, which needs to be investigated if isolated.
Others: group C, G.

Answer 24

Beta-haemolytic streptococci
Group A: more virulent course, similar to S. Aureus.
Group B: usually an acute course. Typically seen in pregnancy.
Group D: streptococcus gallolyticus (previously streptococcus bovis) is a classic cause of subacute IE. It has a strong association with colorectal cancer, which needs to be investigated if isolated.
Others: group C, G.

Question 25

Enterococcus - what is the most commonly implicated enterococcus in IE?

Answer 25

Enterococcus faecalis

Question 26

Fungal causes of IE

Answer 26

Candida species (e.g. C. albicans, C. stellatoidea)
Aspergillus species

Associated with a poor prognosis (~50% mortality)

Question 27

IE is characterised by the formation of vegetations on cardiac …

Answer 27

IE is characterised by the formation of vegetations on cardiac valves.

Question 28

Infective endocarditis - The vegetation can cause local destruction of valves, which leads to regurgitant murmurs and eventually congestive cardiac failure. If this process occurs acutely (e.g. acute IE secondary to Staphylococcal aureus) it can lead to acute heart failure and cardiogenic shock. The order of frequency in which the valves are affected include:

…

Answer 28

The vegetation can cause local destruction of valves, which leads to regurgitant murmurs and eventually congestive cardiac failure. If this process occurs acutely (e.g. acute IE secondary to Staphylococcal aureus) it can lead to acute heart failure and cardiogenic shock. The order of frequency in which the valves are affected include:

Mitral
Aortic
Combined mitral and aortic
Tricuspid
Pulmonary

Question 29

IE is most commonly associated with … (~90%) and cardiac … (~85%).

Answer 29

IE is most commonly associated with fever (~90%) and cardiac murmurs (~85%).

Question 30

The clinical presentation of IE is highly variable depending on the speed of development (… vs …), underlying organism (e.g. … vs …) and patients co-morbidities.

Answer 30

The clinical presentation of IE is highly variable depending on the speed of development (acute vs subacute), underlying organism (e.g. Streptococcal vs Staphylococcal) and patients co-morbidities.

Question 31

Symptoms of IE (7)

Answer 31

Fever (90%)
Malaise, lethargy
Anorexia
Weight loss
Abdominal pain: splenic abscess
Haematuria: renal embolic phenomenon
Cardiac symptoms: shortness of breath, chest pain, palpitations

Question 32

Signs of IE

Answer 32

Cardiac murmur (85%): pansystolic murmur of mitral regurgitation or early diastolic murmur of aortic regurgitation classical
Features of heart failure*: raised JVP, bilateral crackles on respiratory auscultation
Splinter haemorrhages: thin, red to reddish-brown lines of blood under the nails (microemboli)
Petechiae (20-40%): skin and mucous membranes (microemboli and immune complex deposition)
Janeway lesions: nontender erythematous macules on the palms and soles (microabscesses). Acute > subacute.
Osler nodes: tender subcutaneous violaceous nodules mostly on the pads of the fingers and toes (immune complex deposition). Subacute > acute.
Roth spots: exudative, oedematous hemorrhagic lesions of the retina with pale centre (immune complex deposition). Subacute > acute.
Splenomegaly: splenic abscess formation

Question 33

…. …. : nontender erythematous macules on the palms and soles (microabscesses). Acute > subacute.

Answer 33

Janeway lesions: nontender erythematous macules on the palms and soles (microabscesses). Acute > subacute.

Question 34

… … : thin, red to reddish-brown lines of blood under the nails (microemboli)

Answer 34

Splinter haemorrhages: thin, red to reddish-brown lines of blood under the nails (microemboli)

Question 35

raised JVP, bilateral crackles on respiratory auscultation - all features of what?

Answer 35

Heart failure

Question 36

tender subcutaneous nodules on the finger pads and toes - what are these?

Answer 36

Osler nodes

Question 37

exudative haemorrhagic retinal lesions with pale centres - what are these?

Answer 37

Roth spots - exudative haemorrhagic retinal lesions with pale centres

Question 38

Clinical signs of infective endocarditis include:

Answer 38

Janeway lesions - nontender macules on palms and soles
Osler nodes - tender subcutaneous nodules on the finger pads and toes
Roth spots - exudative haemorrhagic retinal lesions with pale centres
Microscopic haematuria and glomerulonephritis
Splinter haemorrhages
PR prolongation or complete AV block - sign of aortic root abscess

Question 39

Complications of infective endocarditis can also be the initial presenting complaint

Answer 39

Acute valvular insufficiency causing heart failure
Neurologic complications e.g. stroke, abscess, haemorrhage (mycotic aneurysm)
Embolic complications causing infarction of kidneys, spleen or lung
Infection e.g. osteomyelitis, septic arthritis

Question 40

Signs and symptoms of…

Answer 40

Infective endocarditis

Question 41

Around 25% of patients with IE have evidence of embolic phenomenon at the time of diagnosis. Peripheral stigmata of IE are increasingly less common due to earlier recognition and diagnosis.

Answer 41

Hands and feet: Osler nodes and Janeway lesions (see above)
Ophthalmological (2%): Roth spots (see above)
Neurological (40%): cerebral abscess, intracerebral haemorrhage, embolic stroke, seizures
Septic emboli (25%): splenic, renal, pulmonary abscesses. Vertebral osteomyelitis, septic arthritis, psoas abscess
Immune reaction (i.e. immune complex deposition): glomerulonephritis, synovitis

Question 42

… and … form the key investigations in the diagnosis of IE.

Answer 42

Echocardiography and blood cultures form the key investigations in the diagnosis of IE.

Question 43

Microbiology - infective endocarditis

Answer 43

Positive microbiology with multiple sets of blood cultures is critical in the diagnosis of IE. In any patient with suspected IE, at least 3 sets of blood cultures should be taken at 30 minute intervals with a good volume of blood per bottle (10 mls). Peripheral cultures should be taken with strict aseptic technique. Ideally, blood cultures should be taken before initiation of systemic antibiotics.

NOTE: pathological examination of resected valvular tissue or embolic fragments remains the diagnostic gold standard.

Question 44

What are the imaging modalities of choice in suspected endocarditis?

Answer 44

Transthoracic echocardiography (TTE) or transoesophgeal echocardiography (TOE)

TTE is a useful initial investigation that is non-invasive. If the TTE is negative or of suboptimal quality, and the index of suspicion is high, then a TOE is performed. In addition, a TOE is performed following a positive TTE to look for local complications (e.g. valve perforation, abscess formation).

Question 45

Findings on TTE/TOE suggestive of IE include:

5

Answer 45

Vegetation
Abscess formation
Pseudoaneurysm
Valve perforation
New dehiscence of a prosthetic valve

Question 46

Other investigations for IE

Answer 46

Bedside: urine dip (haematuria/proteinuria)
ECG: at risk of conduction abnormalities. A prolonged PR interval is suggestive of para-aortic abscess
Bloods: FBC, U&E, CRP/ESR, LFT, Venous blood gas
Thorax and abdominal imaging: CT or US may be needed to look for pulmonary or splenic abscesses
Cerebral imaging: CT or MRI may be needed to assess for neurological complications (even in absence of clinical features)

Question 47

In 2000, the modified … criteria were recommended for the diagnosis of IE.

Answer 47

In 2000, the modified Duke criteria were recommended for the diagnosis of IE.

Question 48

The Modified Duke criteria contains both major and minor criteria that are used to make a diagnosis of IE.

Major criteria? Minor criteria?

Answer 48

Major:
Microbiological criteria: typical microorganisms from two separate blood cultures, OR microorganisms consistent with IE from persistently positive blood cultures (i.e. ≥2 positive cultures from samples ≥12 hours apart, OR, 3 or a majority of ≥4 separate samples taken at least an hour apart).
Evidence of endocardial involvement: echocardiographic evidence of IE (vegetation, abscess, new dehiscence of a prosthetic valve), OR new valvular regurgitation.

Minor criteria

Predisposing heart condition or IVDU
Fever (>38º)
Vascular phenomenon (diagnosed clinically or by imaging): arterial emboli, infectious aneurysm, intracranial haemorrhage, Janeway lesion, conjunctival haemorrhage.
Immunological phenomenon: glomerulonephritis, Osler nodes, Roth spots, rheumatoid factor positive
Microbiological evidence: positive cultures not meeting major criteria. Serological evidence of active infection with organism consistent with IE.

Question 49

Based on the modified duke criteria, IE can be divided into definitive, possible and rejected:

Answer 49

Definite (pathological): vegetation or intracardiac abscess demonstrating active endocarditis on histology, OR microorganism demonstrated by culture or histology of a vegetation or intracardiac abscess
Definite (clinical): 2 major criteria, OR 1 major and 3 minor criteria, OR 5 minor criteria.
Possible: 1 major and 1 minor criteria, OR 3 minor criteria
Rejected: firm alternative diagnosis, OR resolution of symptoms suggesting IE within 4 days of antibiotics, OR no pathological evidence of IE at surgery or autopsy within 4 days of antibiotics, OR does not meet criteria for possible IE.

Question 50

the modified Duke criteria has a lower diagnostic accuracy for … valve endocarditis and …-sided IE.

Answer 50

the modified Duke criteria has a lower diagnostic accuracy for prosthetic valve endocarditis and right-sided IE.

Question 51

The diagnosis of IE should follow the European Society of Cardiology diagnostic algorithm.

Answer 51

Question 52

Prolonged use of … form the cornerstone of treatment of IE.

Answer 52

Prolonged use of antibiotics form the cornerstone of treatment of IE. Antibiotics should always be targeted to the organism that has been cultured with reference to the resistance patterns. This should always be completed in close communication with the endocarditis team (discussed below) or microbiology.

Question 53

Staphylococcus aureus - IE

Answer 53

Methicillin-sensitive staphylococcus aureus (MSSA): flucloxacillin 12 g/day in 4-6 doses. Duration 4-6 weeks.

Methicillin-resistance staphylococcus aureus (MRSA) or penicillin allergy: vancomycin 30-60 mg/kg/day in 2-3 doses. Duration 4-6 weeks.

NOTE: in the presence of a prosthetic valve, rifampicin and gentamicin should be added to both regimens and the duration should be ≥6 weeks.

Question 54

Streptococcal species - IE management

Answer 54

Standard four-week regimen: penicillin G, OR amoxicillin, OR ceftriaxone
Standard two-week regimen: penicillin G, OR amoxicillin, OR ceftriaxone combined with gentamicin.
Penicillin allergic: vancomycin for four weeks

Question 55

When IE is highly suspected, but the organism is not yet known, empirical antibiotics can be started following three sets of blood cultures.

Answer 55

Native valve endocarditis or late prothetic valve endocarditis: Ampicillin, flucloxacillin and gentamicin, OR vancomycin and gentamicin.
Early prosthetic valve endocarditis: vancomycin, gentamicin and rifampicin.

Question 56

Surgery in IE

Answer 56

Up to 50% of patients with IE will require surgery during their inpatient hospital stay. The two main aims of surgery are removal of infected tissue and reconstruction of cardiac anatomy (i.e. valve repair or replacement).

Question 57

There are numerous indications for surgery in IE patients, which can broadly be divided into the following:

Answer 57

Heart failure (e.g. new acute heart failure with haemodynamic compromise)
Uncontrolled infection (e.g. abscess formation or persistently positive blood cultures) 
Prevention of embolisation (e.g. large vegetations >10 mm).

Question 58

Emergency surgery (within … hours)
Urgent surgery (within …)
Elective surgery (within…weeks of antibiotics therapy)

Answer 58

Emergency surgery (within 24 hours)
Urgent surgery (within a few days)
Elective surgery (within 1-2 weeks of antibiotics therapy)

Question 59

Endocarditis team

Answer 59

All patients with strongly suspected or confirmed IE should be referred to the IE team. This team includes, but not limited too, a cardiologist, cardiothoracic surgeon, microbiologist and nurse specialist.

Patients with complicated IE, which refers to IE with heart failure, abscess formation or embolic complications, need referral to a tertiary centre with cardiothoracic facilities.

Question 60

Patients high-risk of developing IE may be offered what?

Answer 60

Patients high-risk of developing IE may be offered prophylactic antibiotics.

Question 61

Prophylactic antibiotics may be prescribed to high-risk patients undergoing high-risk procedures.

High-risk procedures may include:

Answer 61

Cardiac procedures (screening for S. aureus, perioperative prophylaxis may be needed, eliminate source of sepsis ≥2 weeks before procedure)
Dental procedures (manipulation of gingival or perioapical region, local anaesthetic injections, treatment of superficial caries, tooth removal or orthodontic procedures)
Respiratory tract procedures (bronchoscopy, laryngoscopy, transnasal or endotracheal intubation)
Gastrointestinal procedures (transoesophageal echocardiography, gastroscopy, colonoscopy)
Urological procedures (cystoscopy)
Obstetric procedures (vaginal or caesarian delivery)

Question 62

Antibiotic prophylaxis may be used in sub-group of high-risk patients (if benefit is felt to outweigh risk). This group is defined as any patient with:

Answer 62

Prosthetic heart valves or material used for cardiac valve repair
Previous IE
Congenital heart disease (any cyanotic heart disease, those with a lifelong shunt or valvular regurgitation)

Question 63

Prophylactic antibiotics

Options for prophylactic antibiotics for dental procedures (if benefit is felt to outweigh risk) may include:

Answer 63

No penicillin allergy: amoxicillin 2 g orally or IV 30-60 minutes before procedure
Penicillin allergy: clindamycin 600 mg orally or IV 30-60 minutes before procedure

Question 64

… is the most frequent and one of the most severe complications of IE. It is a common indication for surgery.

Answer 64

Heart failure is the most frequent and one of the most severe complications of IE. It is a common indication for surgery.

Question 65

Complications of IE include:

Answer 65

Cardiac (50%): heart failure, perivalvular abscess, pericarditis, cardiac tamponade
Neurological (80% - may be silent): stroke, abscess, meningitis, encephalitis, haemorrhage, seizures
Metastatic infection: mycotic aneurysm, embolisation, abscess formation
Embolisation sequelae: stroke, blindness, ischaemic limb, splenic/renal infarct, pulmonary embolism, myocardial infarction

Question 66

A … interval is strongly suggestive of a developing para-aortic root abscess from perivalvular extension of infection.

Answer 66

A prolonged PR interval is strongly suggestive of a developing para-aortic root abscess from perivalvular extension of infection.

Question 67

The two major complication of aortic valve endocarditis are…

Answer 67

The two major complication of aortic valve endocarditis are para-aortic abscess and valvular insufficiency leading to heart failure. Abscess formation may complicate up to 40% of native valve aortic IE, but is more common in prosthetic valves. Perivalvular extension of infection should always be suspected in patients with new conduction disturbances on the ECG, which commonly includes PR prolongation (i.e. first degree atrioventricular block).

Question 68

A 64-year-old patient presents to ED with fever, shortness of breath and a new-onset cardiac murmur. She has been feeling unwell for the last few weeks with a suspected urinary tract infection. She has a past medical history of rheumatoid arthritis and hypertension. On admission, she is noted to have an early diastolic murmur heard loudest at the left lower sternal edge and a pan systolic murmur heard in the mitral region.

Which of the following investigations are most important to carry out?

A	Urine dip and blood cultures
B	Full blood count & urea and electrolytes
C	ECG and troponins
D	Blood cultures and echocardiography
E	Lactate

Answer 68

D

Any patient with a fever and new murmur should be investigated for suspected IE.

Question 69

IE is associated with a number of clinical features. Classical stigmata of IE include:

Answer 69

Splinter haemorrhages - linear points of bleeding underneath the nails.
Janeway’s lesions - irregular, erythematous, flat, painless macules on the palms and soles.
Osler’s nodes - painful, red, raised lesions found on the hands and feet.
Roth spots - retinal haemorrhages.

The diagnosis of IE is based on the modified Duke’s criteria, which has major and minor criteria. The major criteria are based upon blood cultures and echocardiography.

Question 70

Which of the following is the most common clinical feature in infective endocarditis (IE)?

A	Abdominal pain
B    Fever 
C	Osler nodes
D	Roth spots
E	Haematuria

Answer 70

B FEVER

The other extremely common finding is a new cardiac murmur, which together with fever, is highly suspicious of IE.

Lethargy, anorexia and weight loss are all commonly experienced symptoms, particularly in subacute bacterial IE. The remaining clinical features are largely dependent on the develop of emboli events:

• Abdominal pain: splenic infarcts/abscess
• Osler notes: tender subcutaneous violaceous nodules mostly on the pads of the fingers and toes (immune complex deposition)
• Roth spots: exudative, oedematous hemorrhagic lesions of the retina with pale centre (immune complex deposition)
• Haematuria: development of glomerulonephritis due to immune complex deposition and inflammatory reaction

Question 71

Which of the following organisms is most likely to be implicated in native valve endocarditis?

A	Staphylococcus aureus
B	Alpha-haemolytic streptococci
C	Streptococcus bovis
D	Coagulase negative staphylococci
E	Haemophilus aphrophilus

Answer 71

Streptococci are most commonly implicated in native valve infective endocarditis (IE).
Native valve IE is usually secondary to streptococcal species such as alpha-haemolytic streptococci. Other less common streptococci include Streptococcus bovis, which has been reclassified into four different species including Streptococcus gallolyticus. Enterococci may also be implicated. One of the suspected pathophysiological mechanisms of IE is brief bacteraemia of alpha-haemolytic streptococci from poor dental health that may initiate an infection in a predisposed individual (i.e. an individual with previous rheumatic heart disease or other risk factor).

Question 72

A 38 year old intravenous drug use is admitted to hospital with high fevers and palpitations. He is a known intravenous drug use and was recently treated for cellulitis at an injection site. On this admission his MRSA swab was positive. He has very poor dentition and appears cachexic. On examination he is tachycardic (120 bpm) with blood pressure 134/68 mmHg. There is an early diastolic murmur and bibasal crackles on auscultation of the lung. Three sets of cultures are taken and he is started empirically on co-amoxclav. The working diagnosis is infective endocarditis and a transthoracic echocardiogram is organised for the next day. Initial blood cultures show gram positive cocci in clusters.

Which of the following is the most appropriate antibiotic?

A	Clindamycin
B	Gentamicin
C	Rifampicin
D    Flucloxacillin
E     Vancomycin

Answer 72

Given the likely diagnosis of a Staphylococcus aureus IE and previous MRSA positivity, vancomycin would be the treatment of choice.
Any patient with suspected IE should be discussed with microbiology and ideally referred and reviewed by the IE team. The treatment of choice for a methicillin sensitive staphylococcus aureus (MSSA) would be flucloxacillin. If the patient has methicillin resistant staphylococcus aureus (MRSA), is at risk of this MRSA (e.g. MRSA swab positive) or has coagulase negative staphylococci (CoNS), then vancomycin would be the more appropriate option. In this case, the history of intravenous drug use is concerning for staphylococcus aureus infection and the finding of gram positive cocci in clusters suggests of staphylococci. Remember, Streptococci are gram positive organisms that appear in chains or as diplococci (e.g. streptococcus pneumoniae).

Question 73

The treatment of choice for a methicillin sensitive staphylococcus aureus (MSSA) would be ….

Answer 73

The treatment of choice for a methicillin sensitive staphylococcus aureus (MSSA) would be flucloxacillin.

Question 74

If the patient has methicillin resistant staphylococcus aureus (MRSA), is at risk of this MRSA (e.g. MRSA swab positive) or has coagulase negative staphylococci (CoNS), then … would be the more appropriate option.

Answer 74

vancomycin

Question 75

A … PR interval is strongly suggestive of a developing para-aortic root abscess from perivalvular extension of infection.

Answer 75

A prolonged PR interval is strongly suggestive of a developing para-aortic root abscess from perivalvular extension of infection.

Question 76

A 38 year old intravenous drug use is admitted to hospital with high fevers and palpitations. He is a known intravenous drug use and was recently treated for cellulitis at an injection site. On this admission his MRSA swab was positive. He has very poor dentition and appears cachexic. On examination he is tachycardic (120 bpm) with blood pressure 134/68 mmHg. There is an early diastolic murmur and bibasal crackles on auscultation of the lung. Three sets of cultures are taken and he is started empirically on co-amoxclav. The working diagnosis is infective endocarditis and a transthoracic echocardiogram is organised for the next day. Initial blood cultures show gram positive cocci in clusters.

What antibiotic?

Answer 76

Given the likely diagnosis of a Staphylococcus aureus IE and previous MRSA positivity, vancomycin would be the treatment of choice.