Antibiotic therapy with penicillin, doxycycline, and ceftriaxone has proven to be effective for the treatment of Lyme borreliosis. In some patients, however, it was noticed that borreliae can survive in the tissues in spite of seemingly adequate therapy. For a better understanding of this phenomenon, we investigated the different modes of degeneration of Borrelia burgdorferi suspensions during a 96-h exposure to various antibiotics. By dark-field microscopy and ultrastructural investigations, increasing blebbing and the gradual formation of granular and cystic structures could be followed during the exposure time. Although antibiotic concentrations at the MIC at which 90% of organisms are inhibited after 72 h were 80% or even greater, motile organisms were still present after incubation with penicillin and doxycycline but not after incubation with ceftriaxone. By transmission electron microscopy, intact spirochetal parts, mostly situated in cysts, were seen up to 96 h after exposure with all three antibiotics tested. According to experiences from studies with other spirochetes it is suggested that encysted borreliae, granules, and the remaining blebs might be responsible for the ongoing antigenic stimulus leading to complaints of chronic Lyme borreliosis.Borrelia burgdorferi, the pathogenic agent of Lyme borreliosis, has been recognized as a bacterium that is susceptible to antibiotics. The long-term persistence of these bacteria in tissues, despite adequate treatment of infected patients, has been indicated to be responsible for late complications and a chronic course of disease (17,26,28). The withdrawal of borreliae, or parts of them, into privileged or secluded sites, where they are further inaccessible to antibiotics, raises the question of whether antibiotics themselves can be made responsible for transforming the organism into a persistent, viable, or nonviable but antigenically potent form.Immobilization of bacteria has been seen as a result of incubation with antibiotics in vitro (21). By light microscopy, Preac-Mursic et al. (29) observed blebs, spherical structures, and granules in B. burgdorferi cultures during incubation with antibiotics. In ultrastrucutral studies the action of penicillin on cultures of Borrelia hermsii has been investigated (3).Penicillin, doxycycline, and ceftriaxone are the most preferred antibiotics for treating Lyme borreliosis. Although certain differences in the actions of these antimicrobial agents have been evaluated, they seem to be equally effective (34).Culture experiments were carried out to investigate the actions of these antibiotics on the motility, morphology, and survival of B. burgdorferi during exposure to antibiotic solutions. The course and mode of degeneration of these spirochetes were recorded on a videomicroscope and were photographed with an electron microscope. MATERIALS AND METHODSCulture experiments. Three strains of B. burgdorferi sensu lato, B31 (ATCC 35219) and two isolates from erythema migrans lesions on the skin of patients in Vienna, isolates hig...

The reliability of various in vitro techniques to identify Borrelia burgdorferi infection is still unsatisfactory. Using a high-power resolution videomicroscope and staining with the borrelia genus-specific monoclonal flagellar antibody H9724, we identified borrelial structures in skin biopsies of erythema chronicum migrans (from which borrelia later was cultured), of acrodermatitis chronica atrophicans, and of morphea. In addition to typical borreliae, we noted stained structures of varying shapes identical to borreliae found in a "borrelia-injected skin" model; identical to agar-embedded borreliae; and identical to cultured borreliae following exposure to hyperimmune sera and/or antibiotics. We conclude that the H9724-reactive structures represent various forms of B. burgdorferi rather than staining artifacts. These "atypical" forms of B. burgdorferi may represent in vivo morphologic variants of this bacterium.

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Humoral immune responses to Borrelia burgdorferi (Bb) have been reported to occur in certain patients with circumscribed scleroderma (CS) (morphoea). Together with the isolation of spirochaetes from CS skin biopsies, this finding was taken to suggest Bb as the aetiological agent of CS. Since there is cellular immunoreactivity to Bb in patients with chronic Lyme borreliosis (LB), Bb-specific lymphocytic responses were tested in patients with CS. For this purpose, peripheral blood mononuclear cells from CS patients and, as controls, from patients with various manifestations of LB, and from healthy volunteers without any evidence of Bb infection, were exposed to Bb organisms for 5 days and then assayed for DNA synthesis. Stimulation indices (SI) > 10 were scored positive. By performing lymphocyte proliferation tests we found: (i) that not only patients with various manifestations of LB but also a considerable percentage of seropositive (five of 13 = 38%) and seronegative (six of 26 = 23%) CS patients exhibit an elevated Bb-induced lymphocyte proliferation; (ii) that the magnitude of the cellular response seen in CS patients is comparable to that encountered in patients with established Bb manifestations; and (iii) that, within a given patient, antibiotic therapy can result in a significant reduction of this response. These results support a causative role of Bb in at least some CS patients. Bb-induced lymphocyte responses were also seen in both seropositive and seronegative erythema chronicum migrans patients. These findings show that the pattern of Bb-specific immune responses is more complex than previously thought, and underscore the importance of lymphocyte function assays in evaluating the diagnosis of potential Bb infection in seronegative patients.