Western blot assay using the 23 kDa recombinant peptide. Top left; lane 1, molecular weight standards; lanes 2–3, sera from patients with Leptospira infection; lanes 4–5, sera from patients with Toxoplasma infection; lanes 6–8, sera from patients with dengue virus infection; lane 9, serum from a patient with Rocky Mountain spotted fever; lane 10, serum from a patient with R. typhi infection; lane 11, serum from a patient with R. felis infection; lane 12, serum from a patient with R. akari infection; lane 13, negative control serum; lane 14, mouse polyclonal antibodies to the 23 kDa recombinant peptide. Top right; lane 1, mouse polyclonal antibodies to the 23 kDa recombinant peptide; lane 2–4, sera from patients with R. felis infection; lane 5, negative control serum. Bottom: lanes 1, mouse polyclonal antibodies to the 23 kDa recombinant peptide; lane 2, serum from a patient with R. felis infection; lanes 3–9, sera from patients with Rocky Mountain spotted fever; lanes 10–12, sera from patients with R. akari infection; lanes 13–15, sera from patients with R. typhi infection; lane 16, negative control serum.