Infective endocarditis Flashcards
Aetiology of infective endocarditis?
The strongest risk factor for developing infective endocarditis is a previous episode of endocarditis. The following types of patients are affected:
Previously normal valves (50%, typically acute presentation)
- the mitral valve is most commonly affected
Rheumatic valve disease (30%)
Prosthetic valves
Congenital heart defects
Intravenous drug users (IVDUs)
e.g. typically causing tricuspid lesion)
others: recent piercings
Causes of Infective endocarditis?
Staphylococcus aureus
- now the most common cause of infective endocarditis
particularly common in acute presentation and IVDUs
Streptococcus viridans
- historically Streptococcus viridans was the most common cause of infective endocarditis. This is no longer the case, except in developing countries
- technically Streptococcus viridans is a pseudotaxonomic term, referring to viridans streptococci, rather than a particular organism. The two most notable viridans streptococci are Streptococcus mitis and Streptococcus sanguinis
- they are both commonly found in the mouth and in particular dental plaque so endocarditis caused by these organisms is linked with poor dental hygiene or following a dental procedure
Coagulase-negative Staphylococci such as Staphylococcus epidermidis
- commonly colonize indwelling lines and are the most cause of endocarditis in patients following prosthetic valve surgery, usually the result of perioperative contamination.
- after 2 months the spectrum of organisms which cause endocarditis return to normal (i.e. Staphylococcus aureus is the most common cause)
Streptococcus bovis
- associated with colorectal cancer
- the subtype Streptococcus gallolyticus is most linked with colorectal cancer
Non-infective
- systemic lupus erythematosus (Libman-Sacks)
- malignancy: marantic endocarditis
Culture negative causes of infective endocarditis?
prior antibiotic therapy
Coxiella burnetii
Bartonella
Brucella
HACEK: Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella)
Infective endocarditis diagnosed if? (modified duke criteria)
pathological criteria positive, or
2 major criteria, or
1 major and 3 minor criteria, or
5 minor criteria
Major criteria:
Positive blood cultures
- two positive blood cultures showing typical organisms consistent with infective endocarditis, such as Streptococcus viridans and the HACEK group, or
- persistent bacteraemia from two blood cultures taken > 12 hours apart or three or more positive blood cultures where the pathogen is less specific such as Staph aureus and Staph epidermidis, or
- positive serology for Coxiella burnetii, Bartonella species or Chlamydia psittaci, or
- positive molecular assays for specific gene targets
Evidence of endocardial involvement
- positive echocardiogram (oscillating structures, abscess formation, new valvular regurgitation or dehiscence of prosthetic valves), or
- new valvular regurgitation
Minor criteria: infective endocarditis?
- predisposing heart condition or intravenous drug use
- microbiological evidence does not meet major criteria
- fever > 38ºC
- vascular phenomena: major emboli, splenomegaly, clubbing, splinter haemorrhages, Janeway lesions, petechiae or purpura
- immunological phenomena: glomerulonephritis, Osler’s nodes, Roth spots
Pathological criteria include:
Positive histology or microbiology of pathological material obtained at autopsy or cardiac surgery (valve tissue, vegetations, embolic fragments or intracardiac abscess content)
Infective endocarditis prophylaxis:
NICE recommends the following procedures do not require prophylaxis:
dental procedures
upper and lower gastrointestinal tract procedures
genitourinary tract; this includes urological, gynaecological and obstetric procedures and childbirth
upper and lower respiratory tract; this includes ear, nose and throat procedures and bronchoscopy
The guidelines do however suggest:
any episodes of infection in people at risk of infective endocarditis should be investigated and treated promptly to reduce the risk of endocarditis developing
if a person at risk of infective endocarditis is receiving antimicrobial therapy because they are undergoing a gastrointestinal or genitourinary procedure at a site where there is a suspected infection they should be given an antibiotic that covers organisms that cause infective endocarditis
Poor prognostic factors of infective endocarditis?
Staphylococcus aureus infection
prosthetic valve (especially ‘early’, acquired during surgery)
culture negative endocarditis
low complement levels
Infective endocarditis: Mortality according to organism
staphylococci - 30%
bowel organisms - 15%
streptococci - 5%
antibiotic guidelines: initial blind therapy
Native valve
amoxicillin, consider adding low-dose gentamicin
If penicillin allergic, MRSA or severe sepsis
vancomycin + low-dose gentamicin
If prosthetic valve
vancomycin + rifampicin + low-dose gentamicin
antibiotics: Native valve endocarditis caused by staphylococci
Flucloxacillin
If penicillin allergic or MRSA
vancomycin + rifampicin
Antibiotics: Prosthetic valve endocarditis caused by staphylococci
Flucloxacillin + rifampicin + low-dose gentamicin
If penicillin allergic or MRSA
vancomycin + rifampicin + low-dose gentamicin
Antibiotics: Endocarditis caused by fully-sensitive streptococci (e.g. viridans)
Benzylpenicillin
If penicillin allergic
vancomycin + low-dose gentamicin
Antibiotics: Endocarditis caused by less sensitive streptococci
Benzylpenicillin + low-dose gentamicin
If penicillin allergic
vancomycin + low-dose gentamicin
