Microbiological Testing

Culture, PCR, and serology are used to identify the causative pathogen of infective endocarditis (IE). Blood culture is the most important test, with a minimum of two or three sets recommended for diagnosis. Automated blood culture systems are used in resource-rich countries, with each set of blood cultures consisting of one aerobic and one anaerobic blood culture bottle. Most pathogens causing IE, including many traditionally considered agents of “culture-negative” IE, can be detected in blood cultures by a standard 4–5 days of incubation. Valve PCR is the most important microbiological test for identifying the pathogen in patients who undergo surgery. Valve specimens obtained during surgery are commonly cultured, but valve culture has a low sensitivity and specificity. Culture of embolic lesions may also identify the causative pathogen. Serological testing, which provides indirect evidence of infection, may be useful when the causative pathogen does not grow in blood cultures.