Diagnosis of infective endocarditis (Modified duke criteria)
المؤلف:
APURBA S. SASTRY , SANDHYA BHAT
المصدر:
Essentials Of Medical Microbiology 2021
الجزء والصفحة:
3rd edition , p288-290
2025-10-20
56
The diagnosis of IE is established with the help of a highly sensitive and specific diagnostic schema— known as the modified Duke criteria; which is based on clinical, laboratory, and echocardiographic findings (Table 1).
Table1. Modified Duke criteria for the clinical diagnosis of infective endocarditis.
Blood Cultures
Isolation of the causative microorganism from blood cultures is critical for diagnosis, determination of antimicrobial susceptibility, and planning of treatment. Blood cultures should be collected before antibiotic therapy.
- Two blood culture sets should be collected at an interval of >12hr between 1st and 2nd set
- Alternatively, three blood culture sets can be collected over one hour (e.g. 30 min gap between 1st and 2nd set and 30 min gap between 2nd and 3rd set).
Note: Blood culture set refers to ‘pair of bottles’; collected from different venipuncture sites.
A major criterion can be fulfilled (Table 1), if:
- A typical IE organism is isolated from two separate blood cultures, or
- Agent other than typical IE organisms is isolated persistently from blood cultures (see Table 1) in the absence of an extra-cardiac focus of infection.
A minor criterion is considered to be fulfilled (Table 1) if blood cultures show positive but not meeting major criterion.
Blood culture collection technique and processing is discussed in detail in Chapter 29.
Non-blood-culture Tests
Various non-blood-culture tests that can be used for the diagnosis of IE include:
- Serologic tests can be used to implicate some organisms that are difficult to recover by blood culture: Brucella, Bartonella, Legionella, Chlamydophila psittaci, and Coxiella burnetiid
- Isolation of the pathogens in vegetations by culture
- Microscopic examination with special stains (e.g. periodic acid–Schiff stain for Tropheryma whipplei)
- Direct fluorescence antibody techniques
- PCR to recover unique microbial DNA or 16S rRNA that, when sequenced, allows identification of the etiologic agent.
Echocardiography
Echocardiography allows anatomic confirmation of infective endocarditis, sizing of vegetations, detection of intracardiac complications, and assessment of cardiac function.
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