# Bartonella > Bartonella for MBBS Microbiology: cat-scratch disease, bacillary angiomatosis, trench fever, Carrión disease and Warthin-Starry staining. - Canonical URL: https://prepelephant.com/topics/mbbs/microbiology/bartonella - Exam / course: MBBS · Subject: Microbiology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Bartonella", PrepElephant, https://prepelephant.com/topics/mbbs/microbiology/bartonella ## Direct answer A child with a cat scratch weeks earlier and one tender axillary node should prompt Bartonella henselae before an FNAC for tuberculosis is ordered. Bartonella are small, fastidious, facultatively intracellular gram-negative rods that stain poorly with Gram and best with Warthin-Starry silver; they are culture-negative by routine methods and slow even in enriched or automated systems, so serology and histology carry the diagnosis. Three species define the examinable spectrum: B. henselae — cat-scratch disease (regional lymphadenopathy after a cat scratch or flea bite, usually self-limiting) and, in advanced HIV, bacillary angiomatosis and peliosis hepatis; B. quintana — louse-borne trench fever, now urban homelessness and culture-negative endocarditis; B. bacilliformis — sandfly-transmitted Carrión disease, whose acute phase (Oroya fever) is a dramatic haemolytic anaemia from red cell invasion and whose chronic phase is the vascular tumours of verruga peruana. ## What you must remember - **Morphology and staining:** pleomorphic gram-negative rods, weakly Gram-staining; Warthin-Starry silver stain demonstrates them in tissue — the name to attach to cat-scratch lymph node histology. - **Vectors and reservoirs:** B. henselae — cats are the reservoir and the cat flea (Ctenocephalides felis) the vector; flea faeces inoculated by scratching transmit; B. quintana — human body louse, humans the sole reservoir; B. bacilliformis — Lutzomyia sandflies in Andean valleys. - **Cat-scratch disease:** papule at the inoculation site, then regional lymphadenopathy one to two weeks later (axillary, cervical, epitrochlear), tender with overlying red skin, low fever; suppurates in a minority; usually resolves over weeks to months. - **Uncommon CSD presentations to quote:** Parinaud oculoglandular syndrome (conjunctivitis with preauricular node), neuroretinitis with a macular star, encephalopathy and seizures in children. - **Bacillary angiomatosis:** lobular proliferations of capillaries in skin, bone, liver (peliosis) of severely immunocompromised patients — clinically mimicking Kaposi sarcoma; Warthin-Starry-positive organisms within; treated with prolonged erythromycin or doxycycline. - **Trench fever (B. quintana):** the "five-day fever" of trench warfare — relapsing fever, severe shin pain, sterile blood cultures; today it causes chronic bacteraemia and culture-negative endocarditis in homeless, louse-infested populations. - **Carrión disease (B. bacilliformis):** acute Oroya fever — fever and severe haemolytic anaemia with organisms filling erythrocytes — then weeks later verruga peruana angiomatous skin lesions; Daniel Carrión's fatal self-inoculation proved both phases one disease. - **Diagnosis and therapy:** indirect fluorescent antibody serology is the practical standard, with PCR and prolonged blood culture to confirm; azithromycin shortens bulky CSD; endocarditis needs doxycycline plus gentamicin. ## The AIDS-era angiomatosis, and what it taught Rewind to the early HIV era, before combination antiretroviral therapy: patients with advanced immunosuppression under early NACO-era care in India had no such category yet, but Western cohorts were filling with violaceous skin nodules initially dismissed as Kaposi sarcoma — until biopsies showed not spindle-cell sarcoma but lobular capillary proliferations stuffed with Warthin-Starry-positive bacilli. Epidemiological detective work traced the agent to a new species, Bartonella henselae, and linked the same organism to peliosis hepatis, a blood-filled cystic liver disease in the same patients. The punchline: bacillary angiomatosis melted under prolonged erythromycin or doxycycline — a "tumour" that was a curable infection, reshaping how medicine thinks about vascular proliferation. The same logic returns today: biopsy, not assumption, separates vascular lesions in HIV patients, and B. quintana serology or weeks-long blood cultures name pathogens routine protocols miss in culture-negative endocarditis. ## Where students slip Two vector errors recur: students credit the scratch itself with transmitting B. henselae directly from claw to blood, when the claw inoculates infected flea faeces — the cat is the reservoir, the flea the amplifier; and they assign trench fever to fleas or ticks rather than the body louse. Second slip: reaching for acid-fast or Gram expectations — Bartonella is the Warthin-Starry organism, and calling lymph node biopsy "negative for AFB, so no diagnosis" misses the granulomatous with stellate microabscesses and silver-positive bacilli that define cat-scratch histology. Third, treatment reflexes misfire: CSD in an immunocompetent child usually needs no antibiotic, and the examinable indications are bulky painful nodes, systemic illness, retinitis or immunocompromise. A final Indian angle for viva: cat-scratch disease is under-recognised rather than absent — with abundant street and household cats and fleas, the index of suspicion, backed by serology, is what finds it. ## Frequently asked questions ### Which Bartonella species causes cat-scratch disease, and how is it transmitted? Bartonella henselae, with cats as reservoir and the cat flea as vector; infective flea faeces are inoculated through scratched skin, producing a papule and then regional lymphadenitis. ### Why does bacillary angiomatosis mimic Kaposi sarcoma? Both present as violaceous vascular skin lesions in immunocompromised hosts, but angiomatosis shows capillary lobules with neutrophils and Warthin-Starry-positive bacilli, and it responds to antibiotics. ### What distinguishes the two phases of Carrión disease? The acute Oroya fever phase is an intravascular haemolytic anaemia with bartonellae filling red cells; the chronic verruga peruana phase erupts as angiomatous cutaneous nodules weeks later, both caused by Bartonella bacilliformis. ### What is trench fever, and who gets it now? A relapsing fever with severe shin and back pain transmitted by the human body louse, classically of First World War trenches; today B. quintana also causes chronic bacteraemia and culture-negative endocarditis in homeless populations. ### When should azithromycin be given in cat-scratch disease? For bulky, painful suppurating lymphadenitis, systemic illness, hepatosplenic disease, neuroretinitis, or immunocompromised hosts — while uncomplicated CSD in healthy children is managed supportively.