IN-VIVO ACTIVITIES OF CEFTRIAXONE AND VANCOMYCIN AGAINST BORRELIA SPPIN THE MOUSE-BRAIN AND OTHER SITES

Borrelia burgdorferi, the agent of Lyme disease, and B. turicatae, a n eurotropic agent of relapsing fever, are susceptible to vancomycin in vitro, with an MIC of 0.5 mu g/ml. To determine the activity of vancom ycin in vivo, particularly in the brain, we infected adult immunocompe tent BALB/c and immunodeficient CB-17 scid mice with B. burgdorferi or B. turicatae, The mice were then treated with vancomycin, ceftriaxone as a positive control, or normal saline as a negative control, The ef fectiveness of treatment was assessed by cultures of blood and brain a nd other tissues, Ceftriaxone at a dose of 25 mg/kg of body weight adm inistered every 12 h for 7 to 10 days eliminated cultivable B. burgdor feri or B. turicatae from all BALB/c or scid mice in the study, Vancom ycin at 30 mg/kg administered every 12 h was effective in eliminating infection from immunodeficient mice if treatment was started within 3 days of the onset of infection, If treatment with vancomycin was delay ed for 7 days or more, vancomycin failed to eradicate infection with B . burgdorferi or B. turicatae from immunodeficient mice. The failure o f vancomycin in eradicating established infections in immunodeficient mice was associated with the persistence of viable spirochetes in the brain during antibiotic treatment.