Apicoplast polymorphisms correlated with clindamycin resistance. (A) Polymorphism detection was performed for the organellar genomes (api, apicoplast; mt, mitochondrion) versus the reference 3D7. IQE3502 and IQE4006 represent the mutations we saw in the Peruvian parasites. PCR amplification and sequencing revealed these polymorphisms to be point mutations: A4210C (a) and A4743T (b) in PFC10_API0010, a gene located in the inverted repeat region of the apicoplast genome (IRA, IRB). Mutation T16659C (c) was a synonymous SNP in apicoplast gene PFC10_API0060. The mitochondrion polymorphisms were predicted to be near base pair positions 1690 (d), 4807 (data not shown), and 4947 (e). (B) The peptidyl transferase domain of the 23S rRNA secondary structure was modeled based on E. coli. Mutations of residues (blue letters) were implicated in bacteria and algal chloroplasts resistance to lincosamides. The red circles indicate residues that were mutated in our patient isolates. While A2612U was not correlated with resistance, A2058C was correlated with greater than 100-fold increase in clindamycin in vitro EC50.
