Bartonella clarridgeiae infection in a patient with aortic root abscess and endocarditis

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Introduction: Bartonella species are increasingly recognized as agents of culture-negative endocarditis. However, to date, almost all human cases have been associated with two members of the genus, Bartonella henselae and Bartonella quintana. B. henselae infections are zoonotic, with domestic cats serving as reservoir hosts for the pathogen. Bartonella clarridgeiae also exploits cats as reservoir hosts, but its zoonotic potential is far less established.

Case presentation: A 34-year-old male presented with palpitations after a history of aortic incompetence. During surgery for an aortic valve replacement, two vegetations were found on the aortic valve. PCR analysis of the vegetation demonstrated the presence of Bartonella species and so the patient was treated post-operatively with ceftriaxone and doxycycline, making a good recovery. Further PCR-based analysis of the patient’s aortic vegetation confirmed the presence of B. clarridgeiae .

Conclusion: This report expands the number of Bartonella species associated with endocarditis and provides clear evidence that B. clarridgeiae should be considered a zoonotic pathogen.



Aortic root abscess is a life-threatening complication of endocarditis.  In this case, caused by Bartonella clarridgeiae, a strain of Bartonella found to cause cat scratch disease going back to 1997 by none other than Dr. Breitshwerdt, after a veterinarian was bitten on the finger by a cat:

Important excerpt:

Within 3 weeks he developed headache, fever, and left axillary lymphadenopathy. Initial blood cultures from the cat and veterinarian were sterile. Repeat cultures from the cat grew Bartonella-like organisms with lophotrichous flagella.

This is a reminder that Bartonella, similar to Lyme (borrelia) is fastidious and hard to find.  Most doctors quit after an initial test returns negative.  In this case the patient was lucky enough to be under the observation of a veterinarian who understands this fact and cultured repeatedly.  The issue of strain variation is important as well.  The test is only as good as what it is testing for.

How many patients have had endocarditis caused by Bartonella species that either aren’t considered pathogenic yet OR weren’t picked up in a singular test?  

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