Effects of penicillin, ceftriaxone, and doxycycline on morphology of Borrelia burgdorferi

In vitro activities of fluoroquinolones against the spirochete Borrelia burgdorferi

Little is known to date about the in vitro activity of fluoroquinolones against Borrelia species. Our study aimed at determining the in vitro activities of 15 quinolones against nine isolates of the Borrelia burgdorferi sensu lato complex in addition to one Borrelia valaisiana and one Borrelia bissettii tick isolate. For the determination of MICs, a standardized colorimetric microdilution method was applied. Determination of minimal borreliacidal concentrations providing 100% killing of the final inoculum (MBCs) after 72 h and time-kill experiments were performed by conventional culture in Barbour-Stoenner-Kelly medium in combination with dark-field microscopy. The rank order of potency on a microgram-per-milliliter basis for the substances with in vitro activity against B. burgdorferi was gemifloxacin (MIC at which 90% of the isolates tested are inhibited [MIC(90)], 0.12 microg/ml) > sitafloxacin (MIC(90), 0.5 microg/ml), grepafloxacin (MIC(90), 0.5 microg/ml) > gatifloxacin (MIC(90), 1 microg/ml), sparfloxacin (MIC(90), 1 microg/ml), trovafloxacin (MIC(90), 1 microg/ml) > moxifloxacin (MIC(90), 2 microg/ml), ciprofloxacin (MIC(90), 2 microg/ml) > levofloxacin (MIC(90), 4 microg/ml) > ofloxacin (MIC(90), 8 microg/ml), norfloxacin (MIC(90), 8 microg/ml) > fleroxacin (MIC(90), >16 microg/ml), and pefloxacin (MIC(90), 32 microg/ml) > nalidixic acid (MIC(90), 256 microg/ml). After 72 h of exposure, gemifloxacin was borreliacidal (100% killing) against the isolates investigated at a median MBC of 4 microg/ml. In the other compounds tested, median MBCs were higher (> or =8 microg/ml). Results of electron microscopy and time-kill studies clearly support an in vitro activity of some fluoroquinolones against borreliae. Our study demonstrates for the first time the enhanced in vitro effectiveness of some of the recently introduced 4-quinolones against B. burgdorferi.

In vitro activity of mezlocillin, meropenem, aztreonam, vancomycin, teicoplanin, ribostamycin and fusidic acid against Borrelia burgdorferi

The in vitro susceptibility profile of Borrelia burgdorferi is not yet well defined for several antibiotics. Our study explored the in vitro susceptibility of B. burgdorferi to mezlocillin, meropenem, aztreonam, vancomycin, teicoplanin, ribostamycin and fusidic acid. Minimal inhibitory concentrations (MICs) and minimal borreliacidal concentrations (MBCs) were measured using a standardised colorimetric microdilution method and conventional subculture experiments. MIC values were lowest for mezlocillin (MIC(90), < or =0.06 mg/l) and meropenem (MIC(90), 0.33 mg/l). Vancomycin (MIC(90), 0.83 mg/l) was less effective in vitro. Borreliae proved to be resistant to aztreonam (MIC(90), >32 mg/l), teicoplanin (MIC(90), 6.6 mg/l), ribostamycin (MIC(90), 32 mg/l), and fusidic acid (MIC(90), >4 mg/l). The mean MBCs resulting in 100% killing of the final inoculum after 72 h of incubation were lowest for mezlocillin (MBC, 0.83 mg/l). This study gathered further data on the in vitro susceptibility patterns of the B. burgdorferi complex. The excellent in vitro effectiveness of acylamino-penicillin derivatives and their suitability for the therapy of Lyme disease is emphasised.

Serum-starvation-induced changes in protein synthesis and morphology of Borrelia burgdorferi

It has been demonstrated previously that motile Borrelia burgdorferi cells transform into non-motile cyst-forms when incubated for several weeks in BSKII (a complex medium) lacking rabbit serum. B. burgdorferi cells cannot synthesize fatty acids de novo and serum is thought to provide a source of fatty acids and lipids. When B. burgdorferi cells were serum-starved in defined RPMI medium, -90% of the cells formed spherical cysts within 48 h. Cyst formation was inhibited by tetracycline. Cyst opening and recovery of vegetative cells was rapidly induced by the addition of either BSKII or rabbit serum. The percentage of viable cells recovered from cysts ranged from 2.9% to 52-5%. Viability was inversely proportional to cyst age. Protein synthesis by B. burgdorferi during serum starvation was examined by labelling cells with Tran35S-Label and analysing the labelled proteins by two-dimensional gel electrophoresis and fluorography. The synthesis of over 20 proteins was induced during serum starvation. Western blots of proteins from vegetative cells and cysts probed with sera from either B. burgdorferi-infected humans or monkeys revealed that several cyst proteins were antigenic. These data suggest that cells of B. burgdorferi, although possessing a small genome and extremely limited biosynthetic capabilities, rapidly respond to conditions of serum starvation by inducing changes in protein synthesis and cell morphology. This study may help explain how cells of B. burgdorferi can survive periods of nutrient deprivation in different hosts and host tissues.

An in vitro study of the susceptibility of mobile and cystic forms of Borrelia burgdorferi to metronidazole

The aim of this study was to examine the susceptibility of mobile and cystic forms of Borrelia burgdorferi to metronidazole. Because B. burgdorferi is a microaerobic bacterium like Helicobacter pylori, metronidazole (MZ) was chosen in the susceptibility test. For both microaerobic and aerobic incubation the normal mobile spirochetes were resistant to this antibiotic with an MBC > or = 512 microg/ml. Conversion of mobile spirochetes to cystic forms was not observed when they were incubated with MZ. When they were incubated under microaerobic conditions, the biologically active cystic forms had an MBC > or = 4 microg/ml, but the MBC was > or = 32 microg/ml with aerobic incubation at 37 degrees C. Staining with acridine orange (AO), dark field microscopy (DFM), and transmission electron microscopy (TEM) revealed that the contents of the cysts were degraded when the concentration of MZ was > or = MBC. Some cysts were also ruptured. When incubated with a sufficient concentration of MZ, core structures did not develop inside the cysts, and AO revealed less RNA in the cysts. Our observations may help efforts to treat resistant infections caused by B. burgdorferi with a combination of MZ and other antibiotics in order to eradicate both cystic and mobile forms of B. burgdorferi.

A rapid method for generating cystic forms of Borrelia burgdorferi, and their reversal to mobile spirochetes

Mobile Borrelia burgdorferi were transferred to distilled water (10(6) per ml). The cultures were observed by dark field microscopy (DFM), interference contrast microscopy (ICM) and transmission electron microscopy (TEM). 95% of the spirochetes were converted to cysts after 1 min, and after 4 h no normal mobile borreliae were observed. When transferred to growth medium (BSK-H), the cysts became smaller and more irregular, and were filled with organic substances. After 1 day, 1-5 thin structures sprouted from the cysts. They continued to grow in both length and thickness until they attained a normal spirochetal structure. Finally, these new-born spirochetes detached from the cysts, by which time their mobility had become normal. The present method for producing large amounts of cystic forms of B. burgdorferi is well suited for further studies of this unique microbe.

In vitro conversion of Borrelia burgdorferi to cystic forms in spinal fluid, and transformation to mobile spirochetes by incubation in BSK-H medium

The purpose of this study was to examine the structural alterations of Borrelia burgdorferi when exposed to spinal fluid. Normal, mobile spirochetes were inoculated into spinal fluid, and the spirochetes were converted to cysts (spheroplast L-forms) after 1-24 h. When these cystic forms were transferred to a rich BSK-H medium, the cysts were converted back to normal, mobile spirochetes after incubation for 9 to 17 days. The cultures were examined by dark field microscopy (DFM), interference contrast microscopy (ICM) and transmission electron microscopy (TEM). When neuroborreliosis is suspected, it is necessary to realize that B. burgdorferi can be present in a cystic form, and these cysts have to be recognized by microscopy. This study may also explain why cultivation of spinal fluid often is negative with respect to B. burgdorferi.

Transformation of cystic forms of Borrelia burgdorferi to normal, mobile spirochetes

The purpose of this study was to evaluate the behaviour of Borrelia burgdorferi under controlled conditions. The occurrence of cystic forms of Borrelia burgdorferi in vitro was noted, and these cysts were able to be transformed to normal, mobile spirochetes. B. burgdorferi was cultivated in a commercial culture medium without serum. The spirochetes multiplied only slowly in this medium, and transformation to encysted forms was observed after 1 week. When these cysts were transferred to the same culture medium with rabbit serum, the encysted forms developed into regular, mobile spirochetes after 6 weeks, and their regeneration time was normal. Examination of these cysts in the transmission electron microscope revealed transverse fission inside the cysts. It is probable that similar phenomena may occur in vivo under conditions unfavourable for spirochetes. These observations may help to explain why diagnosis and treatment of B. burgdorferi infections in humans can be difficult.

In vitro activity of trimethoprim against Borrelia burgdorferi

A new culture medium has been developed to evaluate the activity of trimethoprim and sulfamethoxazole against Borrelia burgdorferi in vitro. In this specially modified Barbour-Stoenner-Kelly medium, in which antagonizing substances were reduced to a minimum, trimethoprim was more active against Borrelia burgdorferi than against a sensitive strain of Escherichia coli, but sulfamethoxazole was not active against Borrelia burgdorferi.

Heterogeneity of Borrelia burgdorferi in the skin

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.

Formation and cultivation of Borrelia burgdorferi spheroplast-L-form variants

As clinical persistence of Borrelia burgdorferi in patients with active Lyme borreliosis occurs despite obviously adequate antibiotic therapy, in vitro investigations of morphological variants and atypical forms of B. burgdorferi were undertaken. In an attempt to learn more about the variation of B. burgdorferi and the role of atypical forms in Lyme borreliosis, borreliae isolated from antibiotically treated and untreated patients with the clinical diagnosis of definite and probable Lyme borreliosis and from patient specimens contaminated with bacteria were investigated. Furthermore, the degeneration of the isolates during exposure to penicillin G in vitro was analysed. Morphological analysis by darkfield microscopy and scanning electron microscopy revealed diverse alterations. Persisters isolated from a great number of patients (60-80%) after treatment with antibiotics had an atypical form. The morphological alterations in culture with penicillin G developed gradually and increased with duration of incubation. Pleomorphism, the presence of elongated forms and spherical structures, the inability of cells to replicate, the long period of adaptation to growth in MKP-medium and the mycoplasma-like colonies after growth in solid medium (PMR agar) suggest that B. burgdorferi produce spheroplast-L-form variants. With regard to the polyphasic course of Lyme borreliosis, these forms without cell walls can be a possible reason why Borrelia survive in the organism for a long time (probably with all beta-lactam antibiotics) [corrected] and the cell-wall-dependent antibody titers disappear and emerge after reversion.

Success and failure in the treatment of acrodermatitis chronica atrophicans

To determine the most effective treatment for acrodermatitis chronica atrophicans, several clinical trials were undertaken in recent years to evaluate whether a 2-week course of ceftriaxone would be superior to oral antibiotics. Of the 46 patients suffering from acrodermatitis chronica atrophicans, 14 were treated with ceftriaxone 2g for 15 days. The remaining patients received either oral penicillin V 1.5 million IU t.i.d. or doxycycline 100 mg b.i.d. for 20 to 30 days. Patients were followed up for at least 1 year. Of the 14 ceftriaxone-treated patients four showed incomplete regression of the inflammatory skin changes after 6 to 12 months. Two out of five patients who were monitored for Borrelia burgdorferi DNA excretion were still positive after 12 months as compared to none of six patients who were treated orally for 20-30 days. Six out of 11 patients treated orally for only 20 days needed retreatment after 6 months because of continuing skin manifestations, neuropathy or arthralgia. A 30-day duration of treatment with oral antibiotics and not the chosen antibiotic is crucial for curing acrodermatitis chronica atrophicans. The duration of treatment with ceftriaxone needed for eradication of Borrelia in acrodermatitis chronica atrophicans has yet to be determined in future studies.

Erythema migrans: three weeks treatment for prevention of late Lyme borreliosis

An open, randomized, prospective study was carried out to compare the clinical efficacy and safety of phenoxymethylpenicillin with that of minocycline in the treatment of erythema migrans. Sixty patients (minocycline 30, penicillin 30) were enrolled in the study. The two groups of patients were statistically homogeneous regarding age and sex distribution. IgG and IgM antibodies against Borrelia burgdorferi were determined by ELISA before and after treatment and 1 year thereafter. Thirty-nine patients completed the study. All these patients (penicillin 21, minocycline 18) who received a 21-day course of treatment were free of clinical symptoms of late Lyme borreliosis after 1 year. Serum antibodies against B. burgdorferi could be detected before treatment in 6/21 patients treated with penicillin and 3/18 patients treated with minocycline. After 1 year 8/39 patients were seropositive without any evidence of ongoing disease. In the remaining 21 patients treatment could not be completed with the initial antibiotic due to side effects (penicillin 9/30, minocycline 12/30). One patient, who stopped penicillin treatment at day 14 and one patient who stopped minocycline at day 4, developed fatigue and memory impairment within the observation period. A 3-week course of treatment with penicillin or minocycline is equally effective in treating patients with erythema migrans and preventing late symptoms of Lyme borreliosis.