BARTONELLA HENSELAE INVASION OF FELINE ERYTHROCYTES IN-VITRO

Bartonella henselae, the causative agent of cat scratch disease, estab lishes long-term bacteremia in cats, in which it attaches to and invad es feline erythrocytes (RBC). Feline RBC invasion was assessed in vitr o, based on gentamicin selection for intracellular bacteria or by lase r confocal microscopy and digital sectioning. Invasion rates ranged fr om 2 to 20% of the inoculum, corresponding to infection of less than 1 % of the RBC. Invasion was a slow process, requiring >8 h before signi ficant numbers of intracellular bacteria were detected. Pretreatment o f the bacteria with trypsin, or of the RBC with trypsin or neuraminida se, had no effect, but pronase pretreatment of RBC resulted in a sligh t increase in invasion frequency. The ability to model B. henselae inv asion of feline RBC in vitro should permit identification of bacterial surface components involved in this process and elucidate the signifi cance of RBC invasion to transmission and infection in cats.