We attempted to develop a strain of
Babesia gibsoni resistant to diminazene aceturate (DA), an anti-babesial drug,
in vitro. Since the DA-sensitive
B. gibsoni strain could survive and proliferate in culture medium containing 1
ng/m
l DA, the concentration of DA was gradually increased from 1 to 200
ng/m
l. The results showed that the parasites could survive and proliferate in the medium containing 200
ng/m
l DA, which was much higher than the 50% inhibitory concentration (IC
50) of DA for
B. gibsoni. Subsequently, these parasites were removed from erythrocytes and exposed directly to 200
ng/m
l DA. They were able to survive and invade fresh erythrocytes, though the DA-sensitive
B. gibsoni strain did not survive. Based on these results, the parasites cultured within 200
ng/m
l DA were determined to be a DA-resistant
B. gibsoni strain. In addition, the IC
50 levels of clindamycin, doxycycline and pentamidine for the DA-resistant
B. gibsoni strain were determined. The IC
50 levels of clindamycin, doxycycline and pentamidine for the DA-resistant strain were higher than those for the DA-sensitive strain. The IC
50 of pentamidine for the resistant strain was much greater than that for the DA-sensitive strain. These results indicated that the DA-resistant
B. gibsoni strain could have resistance not only to DA, but also to other anti-babesial drugs. In conclusion, we successfully developed a DA-resistant
B. gibsoni strain
in vitro.
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