Culture-negative endocarditis

Differential Diagnosis

Common Fastidious Organisms

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, homelessness	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

Organisms by Risk Factor

• Homelessness with body lice: Bartonella quintana
• Occupational exposures
  • Butchers, fishermen, homemakers, veterinarians, farmers: Erysipelothrix rhusiopathiae
  • Farmers, veterinarians: Coxiella burnetii, Brucella species
• Intravenous drug use:
  • Right-sided with advanced HIV: Salmonella species, Neisseria subflava
  • Pharyngitis: Corynebacterium diphtheriae
  • Other: Neisseria sicca, Clostridium species, Candida species
• Open heart surgery: Legionella species, non-tuberculous mycobacteria including Mycobacterium avium complex, Nocardia species
• Gastroenteritis: Salmonella species
• Sinusitis: Haemophilus influenzae
• Pneumonitis: Chlamydia psittaci
• Diarrhea: Tropheryma whipplei
• Urinary tract infection: Klebsiella species
• Dental procedures: Kingella kingae, Cardiobacterium hominis, Actinobacillus actinomicetemcomitans, Haemophilus parainfluenzae, Lactobacillus speies
  • Cirrhosis and alcoholism: Campylobacter fetus
  • Immunocompromised patient: Gemella species
  • Intravenous drug use: Eikonella corrodens
  • Urinary tract infection: Haemophilus species
• Sexually-transmitted infection: Neisseria gonorrhoeae
• Medicinal leeches: Aeromonas hydrophila
• Dog or cat exposure: Pasteurella species, Bartonella henselae (cats)
• Cattle exposure with prosthetic valve: Coxiella burnetii, Brucella species
• Pregnancy: Listeria monocytogenes
• Cirrhosis or chronic alcohol use: Bartonella quintana, Erysipelothrix species, Campylobacter species, Aeromonas species, Pasteurella species, Listeria monocytogenes

Investigations

• Blood cultures
  • Routine, modern blood culture incubation will grow almost all easily-cultivable bacteria