Background Lyme disease is caused by infection with the spirochete Borrelia burgdorferi and has become the most common tickborne illness in the world today. Chronic Lyme disease results from persistent spirochetal infection that may be difficult to treat (Johnson & Stricker, Expert Rev Anti-Infect Ther 2004;2:533-57). We have examined the clinical efficacy of an oral antibiotic regimen combining a macrolide with a third-generation cephalosporin in patients with chronic Lyme disease.
Methods One hundred seventy-four adult patients with chronic Lyme disease were included in the study. All patients had clinical and serologic evidence of infection with Borrelia burgdorferi and had failed at least one course of antibiotics. Patients were treated with clarithromycin 500 mg and cefdinir 300 mg taken twice daily in an open-ended protocol. Clinical symptoms of Lyme disease were assessed using a four-point Lyme Disease Symptom Scale (0=none, 1=mild, 2=moderate, 3=severe). CD3(-)CD57(+) natural killer (NK) cells were measured by flow cytometry at the start of combination therapy, as previously described (Stricker & Winger, Immunol Lett 2001;76:43).
Results The mean duration of clarithromycin/cefdinir therapy was 5.64±2.97 months (range, 1-18 months). The mean symptom score decreased significantly in patients treated with the combination regimen, from 2.77±0.45 (severe) prior to treatment to 1.33±0.87 (mild) following treatment (P≤0.0001). Each month of treatment was associated with a symptom score decrease of 0.20. The mean initial level of CD57 NK cells was 60±55 cells/μl (range, 0-303 cells/μl; normal range, 60-360 cells/μl). Similar responses to combination therapy were seen in patients with low vs. normal initial CD57 NK levels, with post-treatment symptom scores of 1.38±0.92 vs. 1.21±0.77 respectively (P=NS). Surprisingly, patients with the lowest CD57 NK levels (≤20 cells/μl) responded as well to the treatment regimen as patients with the highest CD57 NK levels (≥100 cells/μl). The combination antibiotic regimen was well tolerated.
Conclusions The combination of clarithromycin and cefdinir appears to be an effective treatment for patients with chronic Lyme disease. Response to therapy was independent of the initial CD57 NK level. Prolonged antibiotic therapy may be required to treat persistent infection in chronic Lyme disease.