Low oxygen arrests Babesia duncani schizonts and leads to increased drug susceptibilities in hamster erythrocytes

We studied the effect of oxygen concentrations on the in vitro growth and drug susceptibility of Babesia duncani. We found that the growth of B. duncani required high level oxygen and the culture condition at ambient aerobic condition (21% O2) was optimal. Compared with ambient air, our results further showed that low oxygen (6-16%) could arrest B. duncani schizonts and lead to high susceptibilities to antiparasitic drugs atovaquone, pyrimethamine, quinine, and chloroquine at certain concentrations in vitro. Drug susceptibilities of other Babesia spp impacted by O2 levels need to be studied in the future, and this study indicates that culturing conditions of Babesia spp should be considered and reestablished for generating more comparable and reliable results in drug research in the future. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/426147v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@6414b2org.highwire.dtl.DTLVardef@8ad845org.highwire.dtl.DTLVardef@17cd3bcorg.highwire.dtl.DTLVardef@30f1f2_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIThe in vitro growth of B. duncani requires high level oxygen and the culture condition of 5% CO2 ambient air is optimal C_LIO_LILow level oxygen results B. duncani in low growth rate and high schizont ratio in vitro C_LIO_LICompared with 5% CO2 ambient air, in vitro drug susceptibilities of B. duncani can be significantly increased when cultured in microaerobic condition C_LI