A 28-year-old immunocompromised HIV patient (CD4 50 cells/µL) develops recurring bacteraemia with gram-negative bacilli forming small vessel angiomatous lesions on skin (bacillary angiomatosis) and liver (peliosis hepatis). Silver stain of skin biopsy shows clumps of extracellular bacilli. What is the most likely causative organism and treatment?
- A Kaposi sarcoma-associated herpesvirus (KSHV/HHV-8); antiretroviral therapy
- B Bartonella henselae or B. quintana; erythromycin or azithromycin for ≥3 months ✓
- C Rickettsia typhi; doxycycline
- D Mycobacterium avium complex; clarithromycin + ethambutol + rifabutin
Explanation
Bacillary angiomatosis (BA) is caused by Bartonella henselae (cat flea, associated with cats) or B. quintana (human body louse, associated with homelessness/infestation) in immunocompromised hosts, particularly HIV patients with low CD4 counts. Histologically, BA shows lobular vascular proliferation with clumps of bacterial bacilli visible on Warthin-Starry or Steiner silver stain. KS (KSHV) is the main differential but lacks bacterial clumps on silver stain and is managed with ART. Treatment: erythromycin 500 mg QID or doxycycline 100 mg BD for ≥3 months (relapse is common in AIDS).
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.