The long ospC operator version more effectively reduces the activity of a fused flaB promoter in joints of SCID mice. Subgroups of five SCID mice were inoculated with the clone Bp-C/1, Bp-C/2, Co1-Bp-C/1, Co1-Bp-C/2, Co2-Bp-C/1 or Co2-Bp-C/2. One month later, mice were euthanized; heart, joint and skin specimens were used for RNA extraction. RNA samples were quantified for flaB and ospC expression by RT-qPCR. Data are presented as ospC transcripts per 1000 flaB mRNA copy numbers in three groups by combining the subgroups Bp-C/1 and Bp-C/2, Co1-Bp-C/1 and Co1-Bp-C/2, and Co2-Bp-C/1 and Co2-Bp-C/2.