MICROBIOLOGY

• Small fastidious intracellular pleomorphic Gram-negative bacilli.
  • Columbia, Brucella, BHI, and trypticase soy-based agars (all 5% blood supplemented), and chocolate agar are the most frequently used solid media for Bartonella isolation.
  • Human infection occurs by the introduction of infection via flea feces from cats or kittens that become inoculated into the skin, often within new or existing scrapes/scratches.
  • The intracellular lifestyle means recommended antibiotics for treatment (e.g., tetracyclines and macrolides) have good activity within the infected cells.
• Bartonella has > 45 known species, and more than seven cause human disease: B. henselae, B. bacilliformis, B. quintana, B. vinsonii, B. grahamii, B. elizabethae and B. koehlerae.
  • Evolving nomenclature as subspecies classifications, e.g., Bartonella vinsonii subsp. yucatanensi.
• Best seen with Warthin-Starry silver stain or a Brown-Hopps tissue Gram stain.
• The primary reservoir of B. henselae is cats—50% of cats are seropositive and transmitted by saliva contact or scratching ("cat scratch fever" or catch scratch disease [CSD]).
• The menu of diseases caused by Bartonella includes cat scratch disease, retinitis, trench fever, Carrión’s disease [Oroyo fever and verruga peruana], relapsing bacteremia, endocarditis, bacillary angiomatosis, and bacillary peliosis hepatitis.