Short report: cloning of the Babesia gibsoni cytochrome B gene and isolation of three single nucleotide polymorphisms from parasites present after atovaquone treatment.

We determined the nucleotide sequence of the Babesia gibsoni cytochrome b (cytb) gene. DNA was extracted from B. gibsoni isolated from Aomori Prefecture, Japan, and 1,288 basepairs of the cytb gene, including 1,071 basepairs of the open reading frame, were sequenced. The cytb gene of B. gibsoni obtained from three dogs that had been experimentally infected with B. gibsoni and treated with atovaquone was also sequenced. The B. gibsoni cytb gene obtained from all three atovaquone-treated dogs contained a single polymorphism resulting in an amino acid change in one of the putative ubiquinone-binding sites of Plasmodium falciparum. This polymorphism was homologous to mutations in other apicomplexan protozoa that exhibit resistance to atovaquone. Two other single polymorphisms were identified in parasites isolated from two of the dogs. These results indicate that single nucleotide polymorphisms in the sequence for mitochondrial cytb gene may be associated with decreased susceptibility of Babesia species to atovaquone.