DIFFERENTIATION OF BORRELIACIDAL ACTIVITY CAUSED BY IMMUNE SERUM OR ANTIMICROBIAL AGENTS BY FLOW-CYTOMETRY

We demonstrated that borreliacidal activity caused by immune serum and complement can easily be differentiated by flow cytometry from killin g activity caused by antimicrobial agents that are commonly used for t he treatment of Lyme disease. Assay suspensions containing normal or i mmune serum were incubated with Borrelia burgdorferi in the presence o r absence of ceftriaxone, doxycycline, penicillin, and phosphomycin fo r 2, 8, 16 and 24 h. Samples containing killing activity were identifi ed by using flow cytometry and acridine orange. In 30 min, the effects of immune serum and complement were easily distinguished from the kil ling of spirochetes by antimicrobial agents by adding fluorescein isot hiocyanate-conjugated goat anti-hamster immunoglobulin. This simple pr ocedure greatly enhanced the usefulness of the borreliacidal assay by eliminating a major source of false-positive reactions.