Cat-bite-induced Francisella tularensis infection with a false-positive serological reaction for Bartonella quintana

. Tularaemia is caused by infection with Francisella tularensis transmitted via direct contact with an infected hare carcass or indirectly through the bites of vectors, but may be cat-bite-associated as well. Medical history and reliable diagnostic analysis are important in order to differentiate it from other cat-associated infections, e.g. Bartonella spp. Case presentation. A healthy 56-year-old man was examined because of a cat-bite-associated ulceroglandular wound on his right thumb. Nineteen days after the cat bite occurred, a serology test was positive for anti- Bartonella quintana , but negative for anti- F. tularensis . Since Bartonella infections are rare in Sweden, another serology test was analysed 2 weeks later with a positive result for anti- F. tularensis . The patient was treated with doxycycline for 14 days and recovered. The patient was re-sampled after 18 months to obtain a convalescent sample. The acute and the convalescent samples were both analysed at a reference centre, with negative results for anti- Bartonella spp. this time. Conclusion. This case is enlightening about the importance of extending the medical history and re-sampling the patient for antibody detection when the clinical suspicion of cat-bite-associated tularaemia is high. The false-positive result for anti- B. quintana antibodies may have been due to technical issues with the assay, cross-reactivity or both.