Failure to Isolate Borrelia Burgdorferi After Antimicrobial Therapy in Culture-documented Lyme Borreliosis Associated with Erythema Migrans: Report of a Prospective Study

Background: Borrelia burgdorferi, the etiologic agent of Lyme borreliosis, has occasionally been isolated from tissues or body fluids of patients after antimicrobial treatment. A prospective study of patients with Lyme borreliosis associated with erythema migrans (EM) was initiated in Westchester County, New York, to determine: (1) the clinical and laboratory parameters associated with culture positivity, and (2) the microbiologic response to treatment.

Methods: Skin biopsies were performed in patients with EM and cultured for B. burgdorferi in modified Barbour-Stoenner-Kelly medium at 33 degrees C. Subsequent biopsies for culture were performed adjacent to the original biopsy site for culture-positive patients after the completion of antimicrobial therapy.

Results: Initial biopsy cultures were performed for 44 patients; 6 were unevaluable due to culture contamination with other bacteria. Cultures were positive in 21 of 29 patients prior to treatment (72%), but in none of 9 patients during treatment (p < 0.001). The only other identified factor associated with successful recovery of B. burgdorferi was shorter duration of EM. When patients who had received prior antimicrobial therapy were excluded, the mean duration of the EM lesion for those with positive cultures was 5.0 +/- 5.2 days compared with 14.6 +/- 9.9 days for those with negative cultures (p < 0.01). B. burgdorferi could not be reisolated from any of 18 evaluable subsequent biopsies of skin from 13 culture-positive patients 4 to 209 days after completion of a course of antimicrobial therapy. Five patients had negative subsequent biopsy cultures on two separate occasions 3 to 5 months apart.

Conclusions: After brief courses of antibiotics, B. burgdorferi appears to be rapidly eliminated from the skin at EM sites. The ability to recover B. burgdorferi from skin biopsy cultures of untreated patients with EM lesions wanes with increasing duration of EM, suggesting that this organism may also be spontaneously cleared from skin over time.