3.18 Bartonella Henselae

Microbiology review for the USMLE Step 1 exam

• Bartonella henselae is an intracellular gram negative rod that causes several different diseases
• Bartonella targets and lives inside specialized immune cells called CD34+ cells
• Bartonella creates a protective vacuole that protects it and helps it evade immune detection
• Bartonella henselae is a facultative intracellular bacteria
• Three different clinical syndromes associated with bartonella henselae: cat scratch disease, bacillary angiomatosis in immunocompromised patients, and bacterial endocarditis
• Cat scratch disease presents with cutaneous manifestations at the site of inoculation (warm, red, swollen, with a vesicle) and swollen lymph nodes near the site
• Bacillary angiomatosis symptoms include fever, multiple clustered red or violaceous papules or nodules on the skin and mucosa, and bone pain
• Bacterial endocarditis: Bartonella makes its way into the bloodstream and infects the inner surface of the heart
• Bartonella henselae is hard to culture from blood, usually diagnosed via serology
• Treatment depends on the clinical syndrome presented, cat scratch disease is usually self-limited and doesn’t necessarily require antibiotics, bacillary angiomatosis treated with a long 4-month course of either erythromycin or doxycycline.