In vitro inhibitory effect of fosmidomycin on the asexual growth of Babesia bovis and Babesia bigemina

The in vitro inhibitory effect of fosmidomycin was evaluated against the asexual growth of bovine Babesia parasites (Babesia bovis and Babesia bigemina). In the cultures with these parasites, severe reduction of parasite growth was observed by the addition of 1.25 μg/ml of the final drug concentration. Under these conditions, B. bigemina was completely cleared until the third day of cultivation. On the other hand, B. bovis was completely eliminated on the fourth day when the concentration was 6.25 μg/ml in the culture. These parasites failed to grow again when a drug-free medium was substituted for the subsequent cultivation. The IC50 values of fosmidomycin against B. bovis were determined as 0.88 and 0.63 μg/ml in the in vitro cultures with serum-containing M199 and serum-free GIT media, respectively, while it was 0.55 μg/ml against B. bigemina in a serum-containing M199 medium. Severe morphological changes, such as pycnotic and degenerative changes, were preferably observed in the treated parasites. These results suggest that fosmidomycin can be a potent chemotherapeutic agent against bovine babesiosis