Rickettsia vs Coxiella and Bartonella
How to tell Rickettsia and Coxiella and Bartonella apart when a board question makes them look alike.
Rickettsia is arthropod vasculitic rash disease; Coxiella is aerosol livestock Q fever without classic vector bite; Bartonella is cat or louse linked lymph-node or vascular disease.
Side by side
Rickettsia causes vector-borne fever syndromes such as RMSF or typhus, often with severe headache, rash, thrombocytopenia, hyponatremia, and vasculitic endothelial injury.
Coxiella causes Q fever with atypical pneumonia, hepatitis, culture-negative endocarditis, and livestock birth-product aerosol exposure; Bartonella causes cat-scratch lymphadenitis, bacillary angiomatosis, or trench fever.
Rickettsiae are obligate intracellular organisms transmitted by arthropods and infect endothelial cells, causing vasculitis and capillary leak.
Coxiella survives harsh environments as aerosolized particles and replicates intracellularly; Bartonella infects erythrocytes and endothelial cells after cat, flea, or louse exposure.
Rash beginning wrists/ankles then palms/soles, tick exposure, thrombocytopenia, hyponatremia, and serology support RMSF-type Rickettsia.
Q fever serology with pneumonia/hepatitis or culture-negative endocarditis supports Coxiella; Warthin-Starry organisms or cat exposure with tender nodes supports Bartonella.
The trap
These are intracellular zoonotic organisms, but vector, rash, and organ pattern separate them.
The repair move
For intracellular zoonoses, pair the exposure with the syndrome: tick rash, livestock aerosol pneumonia/hepatitis, or cat-scratch nodes.
Try a free question
CoreA patient develops fever, severe headache, thrombocytopenia, hyponatremia, and a rash that begins on wrists and ankles before involving palms and soles after a tick bite. Which organism group is most likely?
Show answer and explanation
Answer: A. Rickettsia. Tick exposure with wrist/ankle rash spreading to palms and soles, thrombocytopenia, and hyponatremia supports RMSF-type Rickettsia.
Why the other choices are tempting
- B. Coxiella causes Q fever from aerosolized livestock exposure and usually lacks a classic rash.
- C. Bartonella causes cat-scratch lymphadenitis, bacillary angiomatosis, or trench fever.
- D. Legionella causes water-linked atypical pneumonia with GI/CNS signs.
- E. Chlamydia pneumoniae causes mild atypical respiratory infection with hoarseness or bronchitis.
Flashcards
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What rash pattern supports Rocky Mountain spotted fever?
Rash starting on wrists and ankles and spreading to palms and soles supports RMSF.
What exposure supports Coxiella burnetii?
Aerosolized livestock birth products or farm exposure supports Coxiella burnetii.
Quick answers
What is the fastest way to tell Rickettsia from Coxiella and Bartonella?
Rickettsia is arthropod vasculitic rash disease; Coxiella is aerosol livestock Q fever without classic vector bite; Bartonella is cat or louse linked lymph-node or vascular disease.
What is the key clue for Rickettsia?
Rickettsia causes vector-borne fever syndromes such as RMSF or typhus, often with severe headache, rash, thrombocytopenia, hyponatremia, and vasculitic endothelial injury.
What is the key clue for Coxiella and Bartonella?
Coxiella causes Q fever with atypical pneumonia, hepatitis, culture-negative endocarditis, and livestock birth-product aerosol exposure; Bartonella causes cat-scratch lymphadenitis, bacillary angiomatosis, or trench fever.
What is the common trap with Rickettsia vs Coxiella and Bartonella?
These are intracellular zoonotic organisms, but vector, rash, and organ pattern separate them.