Culture-negative endocarditis

Organism	Clinical clues	Diagnostic tests
Brucella species	unpasteurized dairy	blood cultures, serology, culture, immunohistology, PCR
Coxiella burnetii	animal exposure (especially pregnant sheep)	serology (IgG phase I >1:800), tissue culture, immunohistology, PCR
Bartonella species	cat exposure, louse exposure, crowding	blood cultures, serology, culture, immunohistology, PCR
Tropheryma whipplei		histology and PCR
Mycoplasma species		serology, culture, immunohistology, PCR
Legionella species		blood cultures, serology, culture, immunohistology, PCR
Fungi	IV drug use, immunocompromise	blood cultures, serology, PCR