Replication Kinetics of Rickettsia raoultii in Tick Cell Lines

is one of the causative agents of tick-borne lymphadenopathy in humans. This bacterium was previously isolated and propagated in tick cell lines; however, the growth characteristics have not been investigated. Here, we present the replication kinetics of in cell lines derived from different tick genera (BME/CTVM23, RSE/PILS35, and IDE8). Tick cell cultures were infected in duplicate with cryopreserved prepared from homologous cell lines. By 12-14 days post infection, 100% of the cells were infected, as visualized in Giemsa-stained cytocentrifuge smears. growth curves, determined by rickettsiae-specific gltA qPCR, exhibited lag, exponential, stationary and death phases. Exponential phases of 4-12 days and generation times of 0.9-2.6 days were observed. in BME/CTVM23 and RSE/PILS35 cultures showed, respectively, 39.5- and 37.1-fold increases compared to the inoculum. In contrast, multiplication of in the IDE8 cultures was 110.1-fold greater than the inoculum with a 7-day stationary phase. These findings suggest variation in the growth kinetics of in the different tick cell lines tested, amongst which IDE8 cells could tolerate the highest levels of replication. Further studies of are needed for a better understanding of its persistence within tick populations.