Comparative in vitro and in vivo susceptibilities of the Lyme disease spirochete Borrelia burgdorferi to cefuroxime and other antimicrobial agents

The In Vitro Antimicrobial Susceptibility of Borrelia burgdorferi sensu lato: Shedding Light on the Known Unknowns

Human Lyme borreliosis (LB) represents a multisystem disorder that can progress in stages. The causative agents are transmitted by hard ticks of the Ixodes ricinus complex that have been infected with the spirochete Borrelia burgdorferi sensu lato. Today, LB is considered the most important human tick-borne illness in the Northern Hemisphere. The causative agent was identified and successfully isolated in 1982 and, shortly thereafter, antibiotic treatment was found to be safe and efficacious. Since then, various in vitro studies have been conducted in order to improve our knowledge of the activity of antimicrobial agents against B. burgdorferi s. l. The full spectrum of in vitro antibiotic susceptibility has still not been defined for some of the more recently developed compounds. Moreover, our current understanding of the in vitro interactions between B. burgdorferi s. l. and antimicrobial agents, and their possible mechanisms of resistance remains very limited and is largely based on in vitro susceptibility experiments on only a few isolates of Borrelia. Even less is known about the possible mechanisms of the in vitro persistence of spirochetes exposed to antimicrobial agents in the presence of human and animal cell lines. Only a relatively small number of laboratory studies and cell culture experiments have been conducted. This review summarizes what is and what is not known about the in vitro susceptibility of B. burgdorferi s. l. It aims to shed light on the known unknowns that continue to fuel current debates on possible treatment resistance and mechanisms of persistence of Lyme disease spirochetes in the presence of antimicrobial agents.

Lyme Disease Frontiers: Reconciling Borrelia Biology and Clinical Conundrums

Lyme disease is a complex tick-borne zoonosis that poses an escalating public health threat in several parts of the world, despite sophisticated healthcare infrastructure and decades of effort to address the problem. Concepts like the true burden of the illness, from incidence rates to longstanding consequences of infection, and optimal case management, also remain shrouded in controversy. At the heart of this multidisciplinary issue are the causative spirochetal pathogens belonging to the Borrelia Lyme complex. Their unusual physiology and versatile lifestyle have challenged microbiologists, and may also hold the key to unlocking mysteries of the disease. The goal of this review is therefore to integrate established and emerging concepts of Borrelia biology and pathogenesis, and position them in the broader context of biomedical research and clinical practice. We begin by considering the conventions around diagnosing and characterizing Lyme disease that have served as a conceptual framework for the discipline. We then explore virulence from the perspective of both host (genetic and environmental predispositions) and pathogen (serotypes, dissemination, and immune modulation), as well as considering antimicrobial strategies (lab methodology, resistance, persistence, and clinical application), and borrelial adaptations of hypothesized medical significance (phenotypic plasticity or pleomorphy).

In vitro and in vivo evaluation of cephalosporins for the treatment of Lyme disease

Background

Lyme disease accounts for >90% of all vector-borne disease cases in the United States and affect ~300,000 persons annually in North America. Though traditional tetracycline antibiotic therapy is generally prescribed for Lyme disease, still 10%–20% of patients treated with current antibiotic therapy still show lingering symptoms.

Methods

In order to identify new drugs, we have evaluated four cephalosporins as a therapeutic alternative to commonly used antibiotics for the treatment of Lyme disease by using microdilution techniques like minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). We have determined the MIC and MBC of four drugs for three Borrelia burgdorferi s.s strains namely CA8, JLB31 and NP40. The binding studies were performed using in silico analysis.

Results

The MIC order of the four drugs tested is cefoxitin (1.25 µM/mL) > cefamandole (2.5 µM/mL), > cefuroxime (5 µM/mL) > cefapirin (10 µM/mL). Among the drugs that are tested in this study using in vivo C3H/HeN mouse model, cefoxitin effectively kills B. burgdorferi. The in silico analysis revealed that all four cephalosporins studied binds effectively to B. burgdorferi proteins, SecA subunit penicillin-binding protein (PBP) and Outer surface protein E (OspE).

Conclusion

Based on the data obtained, cefoxitin has shown high efficacy killing B. burgdorferi at concentration of 1.25 µM/mL. In addition to it, cefoxitin cleared B. burgdorferi infection in C3H/HeN mice model at 20 mg/kg.

In vitro susceptibility of Borrelia burgdorferi isolates to three antibiotics commonly used for treating equine Lyme disease

Background

Lyme disease in humans is predominantly treated with tetracycline, macrolides or beta lactam antibiotics that have low minimum inhibitory concentrations (MIC) against Borrelia burgdorferi. Horses with Lyme disease may require long-term treatment making frequent intravenous or intramuscular treatment difficult and when administered orally those drugs may have either a high incidence of side effects or have poor bioavailability. The aim of the present study was to determine the in vitro susceptibility of three B. burgdorferi isolates to three antibiotics of different classes that are commonly used in practice for treating Borrelia infections in horses.

Results

Broth microdilution assays were used to determine minimum inhibitory concentration of three antibiotics (ceftiofur sodium, minocycline and metronidazole), for three Borrelia burgdorferi isolates. Barbour-Stoner-Kelly (BSK K + R) medium with a final inoculum of 10⁶Borrelia cells/mL and incubation periods of 72 h were used in the determination of MICs. Observed MICs indicated that all isolates had similar susceptibility to each drug but susceptibility to the tested antimicrobial agents varied; ceftiofur sodium (MIC = 0.08 μg/ml), minocycline hydrochloride (MIC = 0.8 μg/ml) and metronidazole (MIC = 50 μg/ml).

Conclusions

The MIC against B. burgorferi varied among the three antibiotics with ceftiofur having the lowest MIC and metronidazole the highest MIC. The MIC values observed for ceftiofur in the study fall within the range of reported serum and tissue concentrations for the drug metabolite following ceftiofur sodium administration as crystalline-free acid. Minocycline and metronidazole treatments, as currently used in equine practice, could fall short of attaining MIC concentrations for B. burgdorferi.

In Vitro Susceptibility of the Relapsing-Fever Spirochete Borrelia miyamotoi to Antimicrobial Agents

Hard-tick-borne relapsing fever (HTBRF) is an emerging infectious disease throughout the temperate zone caused by the relapsing-fever spirochete Borrelia miyamotoi Antibiotic treatment of HTBRF is empirically based on the treatment of Lyme borreliosis; however, the antibiotic susceptibility of B. miyamotoi has not been studied to date. Thus, we set out to determine the in vitro antimicrobial susceptibility of B.miyamotoi A microdilution method with 96-well microtiter plates was used to determine the antibiotic susceptibilities of two B.miyamotoi strains isolated on two different continents (Asia and North America), two Borrelia burgdorferisensu lato strains, and one Borrelia hermsii isolate for purposes of comparison. The MIC and minimal bactericidal concentration (MBC) were determined by both microscopy and colorimetric assays. We were able to show that relative to the B. burgdorferi sensu lato isolates, both B.miyamotoi strains and B. hermsii demonstrated greater susceptibility to doxycycline and azithromycin, equal susceptibility to ceftriaxone, and resistance to amoxicillin in vitro The MIC and MBC of amoxicillin for B. miyamotoi evaluated by microscopy were 16 to 32 mg/liter and 32 to 128 mg/liter, respectively. Since B. miyamotoi is susceptible to doxycycline, azithromycin, and ceftriaxone in vitro, our data suggest that these antibiotics can be used for the treatment of HTBRF. Oral amoxicillin is currently used as an alternative for the treatment of HTBRF; however, since we found that the B. miyamotoi strains tested were resistant to amoxicillin in vitro, this issue warrants further study.

Evidence assessments and guideline recommendations in Lyme disease: the clinical management of known tick bites, erythema migrans rashes and persistent disease

Evidence-based guidelines for the management of patients with Lyme disease were developed by the International Lyme and Associated Diseases Society (ILADS). The guidelines address three clinical questions - the usefulness of antibiotic prophylaxis for known tick bites, the effectiveness of erythema migrans treatment and the role of antibiotic retreatment in patients with persistent manifestations of Lyme disease. Healthcare providers who evaluate and manage patients with Lyme disease are the intended users of the new ILADS guidelines, which replace those issued in 2004 (Exp Rev Anti-infect Ther 2004;2:S1-13). These clinical practice guidelines are intended to assist clinicians by presenting evidence-based treatment recommendations, which follow the Grading of Recommendations Assessment, Development and Evaluation system. ILADS guidelines are not intended to be the sole source of guidance in managing Lyme disease and they should not be viewed as a substitute for clinical judgment nor used to establish treatment protocols.

Culture of the entire mouse to determine whether cultivable Borrelia burgdorferi persists in infected mice treated with a five-day course of Ceftriaxone

Although controversial, it has been suggested that antibiotic treatment of laboratory animals infected with Borrelia burgdorferi often leads to the persistence of residual spirochetes that are claimed to be viable but noncultivable. If viable cells of B. burgdorferi do persist following antibiotic therapy, one possible explanation for the lack of cultivability is that too few organisms persist in any given tissue site that might be sampled and cultured. In this study, we treated SKH (hairless) mice, with B. burgdorferi infection of 3 months' duration, with either ceftriaxone or saline for 5 days and then cultured a suspension extract of nearly the entire mouse using a combined in vivo/in vitro culture method. All of the saline-treated (control) mice were culture positive, compared with none of the antibiotic-treated mice. Our findings further document the effectiveness of antibiotic therapy in eradicating cultivable cells of B. burgdorferi, irrespective of tissue or organ site.

Ineffectiveness of tigecycline against persistent Borrelia burgdorferi

The effectiveness of a new first-in-class antibiotic, tigecycline (glycylcycline), was evaluated during the early dissemination (1 week), early immune (3 weeks), or late persistent (4 months) phases of Borrelia burgdorferi infection in C3H mice. Mice were treated with high or low doses of tigecycline, saline (negative-effect controls), or a previously published regimen of ceftriaxone (positive-effect controls). Infection status was assessed at 3 months after treatment by culture, quantitative ospA real-time PCR, and subcutaneous transplantation of joint and heart tissue into SCID mice. Tissues from all saline-treated mice were culture and ospA PCR positive, tissues from all antibiotic-treated mice were culture negative, and some of the tissues from most of the mice treated with antibiotics were ospA PCR positive, although the DNA marker load was markedly decreased compared to that in saline-treated mice. Antibiotic treatment during the early stage of infection appeared to be more effective than treatment that began during later stages of infection. The viability of noncultivable spirochetes in antibiotic-treated mice (demonstrable by PCR) was confirmed by transplantation of tissue allografts from treated mice into SCID mice, with dissemination of spirochetal DNA to multiple recipient tissues, and by xenodiagnosis, including acquisition by ticks, transmission by ticks to SCID mice, and survival through molting into nymphs and then into adults. Furthermore, PCR-positive heart base tissue from antibiotic-treated mice revealed RNA transcription of several B. burgdorferi genes. These results extended previous studies with ceftriaxone, indicating that antibiotic treatment is unable to clear persisting spirochetes, which remain viable and infectious, but are nondividing or slowly dividing.

Antibiotic treatment of animals infected with Borrelia burgdorferi

Despite resolution of the objective manifestations of Lyme disease after antibiotic treatment, a minority of patients have fatigue, musculoskeletal pain, and/or difficulties with concentration or short-term memory of uncertain etiology; these are called post-Lyme disease symptoms or, in more severe cases, post-Lyme disease syndrome or "chronic Lyme disease." Several recent studies in which Borrelia burgdorferi-infected animals were treated with antibiotic therapy have demonstrated the presence of PCR positivity for B. burgdorferi DNA in the absence of culture positivity. In mice that were treated with antibiotic therapy, residual spirochetes could be taken up by ticks during a blood meal and could be transmitted to SCID mice. These spirochetes are attenuated; their presence is not associated with either inflammation or disease. In this review the methodology and findings of these studies are critically analyzed, and the significance of the results with regard to human Lyme disease is evaluated, with special emphasis on whether these studies provide useful insights into post-Lyme disease syndrome. A serious methodological concern is the failure to consider the pharmacokinetic-pharmacodynamic properties of the antibiotic in choosing the dosage regimen used. We conclude that there is no scientific evidence to support the hypothesis that such spirochetes, should they exist in humans, are the cause of post-Lyme disease syndrome.

A sustained-release formulation of doxycycline hyclate (Atridox) prevents simultaneous infection of Anaplasma phagocytophilum and Borrelia burgdorferi transmitted by tick bite

Current prophylaxis for infected tick bites consists of personal protective measures directed towards ticks. This study compared the efficacy of a single oral dose of doxycycline with that of a single injection of sustained-release doxycycline in a model of Lyme borreliosis and Anaplasma phagocytophilum infection. Dosages of doxycycline were equilibrated based on previously determined peak plasma levels in mice [oral, 2.4 microg (ml plasma)(-1); sustained release, 1.9 microg (ml plasma)(-1)] determined 8 h after inoculation. In challenge experiments where five Borrelia burgdorferi-infected and five A. phagocytophilum-infected nymphs were used per mouse, only 20 and 30 % of mice were protected from B. burgdorferi and A. phagocytophilum infection, respectively, using oral doxycycline. In contrast, 100 % of mice receiving sustained-release doxycycline were protected from A. phagocytophilum infection, as indicated by real-time PCR of blood samples, quantitative PCR and culture isolation of spleen samples, and protected against B. burgdorferi infection as demonstrated by culture of ear, heart and bladder. Although 15-40 copies of A. phagocytophilum could be amplified from the spleens of mice treated with sustained-release doxycycline, no viable A. phagocytophilum from these spleens could be cultured in HL-60 cells. In contrast, 7/10 mice receiving oral doxycycline were PCR- and culture-positive for A. phagocytophilum, with copy numbers ranging from 800 to 10 000 within the spleen, as determined by quantitative PCR. Other correlates with A. phagocytophilum infection included a significant difference in spleen mass (mean of 110 mg for sustained-release treatment versus a mean of 230 mg for oral treatment) and the number of splenic lymphoid nodules (mean of 8 for sustained-release treatment versus mean of 12.5 for oral doxycycline) as determined by histopathology. These studies indicate that a single injection of a sustained-release formulation antibiotic may offer a viable prophylactic treatment option for multiple infectious agents in patients presenting with tick bites.

[Microbiological and pharmacological data useful for the treatment of Lyme disease. Treatment and follow up of early Lyme disease (erythema migrans)]

The aim of this review was first to analyze the microbiological and pharmacological criteria used to choose a treatment for Lyme disease. The determination of Borrelia burgdorferi sensu lato susceptibility to antibiotics is difficult, especially because of the lack of standardization in the methods used. In vitro data is helpful to determine Lyme treatment but discrepancies between in vitro and in vivo results highlight the need to confirm this data by clinical trials. The second part is an analysis of the literature made to evaluate the current strategies of treatment and follow up of early Lyme disease characterized by erythema migrans (EM). beta-lactams (penicillin G and V, amoxicillin, cefuroxime axetil, ceftriaxone), tetracyclines (doxycycline), and macrolides (mainly azithromycin) are the drugs most frequently used during clinical trials. The comparison between treatments is difficult because of the lack of reliable clinical and biological criteria to identify complete recovery. However the prognosis of treated EM is good in most trials. If a clinical follow-up remains necessary after the treatment of an EM, prolonged antibody production among asymptomatic patients reduces the interest of a serological follow-up.

Le traitement des phases secondaires et tertiaires de la borréliose de Lyme

The treatment of secondary and tertiary Lyme borreliosis is difficult because of antibiotic lack of efficacy. This fact may be explained by several factors: the specific pathophysiology, involving not only the presence of bacteria, but also immunological reactions. There is no specific method of diagnosis resulting in difficulties for good indication of treatment and to evaluate treatment efficacy. The literature review shows that ceftriaxone and doxycycline are the two most efficient antibiotics in this indication. Even if the methodology of the published studies is not always convincing, these two antibiotics proved their efficacy in articular as well as in neurological forms of the disease. In the late stage of borreliosis, antibiotics are less efficient. Various treatment modalities with different dosage or duration of treatment cannot let us conclude on a convincing regimen.

[Lyme disease: prophylaxis after tick bite]

Lyme disease is a bacterial infection caused by Borrelia burgdorferi, which is transmitted by infected ticks. The transmission depends on several factors, especially on the duration of the tick's presence in the host body (the nymph which is smaller than the adults and thus less visible, is in this case the most frequently involved) and on whether the tick is infected or not. The interpretation of results in the few available studies is made difficult by the lack of information obtained (due to difficulty to collect information and examination costs). The comparison is made even more difficult by the difference between Borrelia ticks species in various regions. Today, the best methods are preventive: protective clothing, tick repellents, checking and removal of ticks after a journey in an endemic zone, and in case of tick bite, regular examination of the bite site during the following weeks in order to initiate an early curative treatment if ECM is diagnosed. The currently available data seems to be insufficient to suggest systematic antimicrobial prophylaxis in case of tick bite.

Antimicrobial susceptibility of Borrelia burgdorferi sensu lato: what we know, what we don't know, and what we need to know

Human Lyme borreliosis is a multisystem disorder that can progress in stages and is transmitted by ticks of the Ixodes ricinus complex infected with the spirochete Borrelia burgdorferi sensu lato. Today, Lyme borreliosis is regarded as the most important human tickborne illness in the northern hemisphere. Soon after the causative agent was correctly identified and successfully isolated in 1982, antibiotic treatment was shown to be effective and since then a variety of in vitro and in vivo studies have been performed to further characterize the activity of antimicrobial agents against B. burgdorferi s.l. Although many antimicrobial agents have been tested for their in vitro activity against borreliae, the full spectrum of antibiotic susceptibility in B. burgdorferi s.l. has not been defined for many compounds. Moreover, our current understanding of possible antimicrobial resistance mechanisms in B. burgdorferi s.l. is limited and is largely founded on in vitro experiments on relatively few borrelial isolates. This review will summarize what is and what is not known about antimicrobial resistance in B. burgdorferi s.l. and will discuss open questions that continue to fuel the current debate on treatment-resistant Lyme borreliosis.

The clinical assessment, treatment, and prevention of lyme disease, human granulocytic anaplasmosis, and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America

Evidence-based guidelines for the management of patients with Lyme disease, human granulocytic anaplasmosis (formerly known as human granulocytic ehrlichiosis), and babesiosis were prepared by an expert panel of the Infectious Diseases Society of America. These updated guidelines replace the previous treatment guidelines published in 2000 (Clin Infect Dis 2000; 31[Suppl 1]:1-14). The guidelines are intended for use by health care providers who care for patients who either have these infections or may be at risk for them. For each of these Ixodes tickborne infections, information is provided about prevention, epidemiology, clinical manifestations, diagnosis, and treatment. Tables list the doses and durations of antimicrobial therapy recommended for treatment and prevention of Lyme disease and provide a partial list of therapies to be avoided. A definition of post-Lyme disease syndrome is proposed.

Susceptibility of Borrelia afzelii strains to antimicrobial agents

The aim of the present study was to determine the susceptibility of Borrelia afzelii strains to antibiotics, and to test the hypothesis that persistence of borrelia in skin, after therapy, is a consequence of resistance to the antibiotic used for treatment. Ten B. afzelii strains isolated from skin of seven adult patients (two with acrodermatitis chronica atrophicans, five with erythema migrans) were studied. In three patients B. afzelii was isolated from erythema migrans lesion before antibiotic therapy and 2-3 months after treatment with cefuroxime axetil (two patients) or with ceftriaxone (one patient). MICs and MBCs for amoxicillin, azithromycin, ceftriaxone, cefuroxime, doxycycline and amikacin were measured. There was total resistance to amikacin but isolates were susceptible to all other antibiotics except one isolate that was resistant to cefuroxime, MIC > 4 mg/L. Comparison of MBC values after 3 and 6 weeks' incubation revealed comparable results for azithromycin and ceftriaxone while for amoxicillin, cefuroxime and doxycycline, some differences were found. In one of the patients from whom there were borrelia isolated before and after treatment with cefuroxime axetil, both isolates were resistant to cefuroxime. In the other two patients, the paired isolates were susceptible to the antibiotic used for therapy.

Review of treatment options for lyme borreliosis

Lyme borreliosis (Lyme disease) is the most common tick-borne bacterial infection and the incidence is increasing in parts of Europe and the USA. Prompt antimicrobial therapy using oral agents such as doxycycline or amoxicillin is successful among more than 90% of patients. Inadequate penetration of oral agents into the CNS may result in the development of overt neuroborreliosis. The parenteral agent ceftriaxone is the drug of choice for severe acute and chronic infections, due to good penetration into CSF, convenient single daily dosage regimen and proven high efficacy in clinical trials involving a wide variety of disseminated infections. Regardless of therapeutic agent, there appears to a small minority of patients (<10%) who do not respond; such cases may be due to long-term persistence of borrelial cysts and to misdiagnoses based solely on seropositivity. Several adjunct therapies are available, including hyperbaric oxygen therapy and immune system supplements, but clinical trials have yet to be conducted.

Sustained-release formulation of doxycycline hyclate for prophylaxis of tick bite infection in a murine model of Lyme borreliosis

The prophylactic potential of a single injection of sustained-release doxycycline hyclate (Atridox) was compared to that of a single oral dose of doxycycline hyclate in a murine model of Lyme borreliosis. Prophylaxis, as measured by the lack of cultivable spirochetes and demonstrable pathology, was noted for 43% of orally treated mice; in contrast, the sustained-release doxycycline hyclate completely protected mice from infection and resultant pathology.

Diagnosis, treatment, and prevention of Lyme disease in children

The approaches to diagnosing and treating Lyme disease (LD) have been improved and refined as a result of basic and clinical research, and considerable practical experience. In addition, there have been recent studies that have allowed improvements in the ability to prevent infection with Borrelia burgdorferi. This paper will review the relevant literature and address recent developments in the diagnosis, treatment, and prevention of LD. Issues specifically related to the management of children will be identified. Controversies regarding treatment approaches will be examined in some detail. Understanding the clinical manifestations, or stage, of LD is crucial when approaching both diagnosis and treatment. Early localized disease is best diagnosed by recognizing the characteristic skin lesion, erythema migrans. Early disease will frequently, but not always, be accompanied by a detectable antibody response, particularly IgM antibody to the spirochete. Late disease, chiefly arthritis, is generally associated with high levels of IgG antibody. Western blot technology allows confirmation of enzyme immunoassay results and is especially useful when the latter is in the low or equivocal range. Early localized disease responds well to oral antibacterial therapy. Early disseminated disease, often associated with neurologic findings, may require parenteral therapy. The arthritis associated with LD frequently responds to oral antibacterials, but some refractory cases may require intravenous therapy, and occasionally surgery. Doxycycline is the oral antibacterial of choice, while amoxicillin and cefuroxime axetil are alternatives that may be preferred in young children. Owing to its long half-life and once daily dose administration, intravenous ceftriaxone has become the accepted standard for parenteral therapy. Tick avoidance has long been the mainstay for preventing LD. Antibacterial prophylaxis, using doxycycline, for tick bites has been shown to be an effective approach to prevention, but its relevance to pediatrics is uncertain. Vaccines designed to prevent infection have also been developed.

Erythromycin resistance in Borrelia burgdorferi

Susceptibility testing of laboratory strains and clinical isolates of Borrelia burgdorferi indicates that resistance to erythromycin is present in them. Evaluation of the MICs, minimal bactericidal concentrations, and kinetics of bacterial killing of erythromycin suggests that this resistance is increased by preexposure to the antibiotic, is dependent on inoculum size, and may be the result of selection of subpopulations of bacterial cells with increased resistance.

Comparative study of cefuroxime axetil versus amoxicillin in children with early Lyme disease

Cefuroxime axetil has been shown to have efficacy comparable to doxycycline in adults with early Lyme disease (LD). Because of toxicity, doxycycline is usually avoided in children. For children who are unable to tolerate amoxicillin, there is currently no proven alternative oral therapy for LD. This randomized, unblinded study compared 2 dosage regimens of cefuroxime axetil (20 mg/kg/d and 30 mg/kg/d) with amoxicillin (50 mg/kg/d), each given for 20 days. Children were enrolled if they were 6 months to 12 years of age, had erythema migrans, and met other eligibility requirements. Serologic testing occurred at entry and after 6 months. Follow-up evaluations for safety, tolerability, and efficacy occurred at 10 and 20 days, 6 months, and 1 year. Forty-three children were randomized (13 in the amoxicillin group, 15 in each cefuroxime axetil group); 39 completed 12 months of follow-up. At the completion of treatment, there was total resolution of erythema migrans in 67% of the amoxicillin group, 92% of the low-dose cefuroxime group, and 87% of the high-dose cefuroxime group, and resolution of constitutional symptoms occurred in 100%, 69%, and 87%, respectively. All patients had a good outcome, with no long-term problems associated with LD. One patient, who was well at the first 2 follow-up visits, was treated with doxycycline because of new constitutional symptoms. Mild diarrhea occurred in a small number of participants in each group (1 patient was diagnosed and treated for Clostridium difficile-associated diarrhea, which occurred after completing the full course of study medication). No hypersensitivity reactions occurred. The number of patients in this trial was not sufficient to demonstrate a statistically significant difference between the 3 groups; however, both amoxicillin and cefuroxime axetil seem to be safe, efficacious treatments for children with early LD.

Standardised in vitro susceptibility testing of Borrelia burgdorferi against well-known and newly developed antimicrobial agents--possible implications for new therapeutic approaches to Lyme disease

Lyme disease represents a disorder of potentially chronic proportions, and relatively little is known about the in vivo pharmacodynamic interactions of antimicrobial agents with borreliae. So far, evidence-based drug regimens for the effective treatment of Lyme disease have not been definitively established. Moreover, therapeutic failures have been reported for almost every suitable antimicrobial agent currently available. Resistance to treatment and a protracted course of the disease, therefore, continue to pose problems for clinicians in the management of patients suffering from chronic Lyme disease. Further characterisation of the antibiotic susceptibility pattern and a better understanding of the interactions of B. burgdorferi with antimicrobial agents are urgently needed and continue to be crucial owing to considerable differences in the experimental conditions and test methods applied. The development of easily performed, new techniques for the sensitivity testing of B. burgdorferi provides the opportunity to study factors affecting the bacteriostatic and bactericidal action of recently introduced chemotherapeutic agents under more standardised conditions. For the first time, these studies provide direct evidence that, in addition to beta-lactams, macrolides, and tetracyclines which are recommended for stage-dependent treatment of Lyme borreliosis, other recently introduced substances, such as fluoroquinolones, everninomycins, and the ketolide family of antimicrobial agents, also show enhanced in vitro activity against borreliae. Some of these compounds, if effective in vivo as well, may prove to be useful agents in the treatment of certain manifestations of Lyme disease. As such, their potential role should be evaluated further by in vivo experiments and clinical trials. Finally, these antimicrobial agents may turn out to be very effective therapeutic alternatives on account of their oral availability, favourable pharmacodynamic profiles, and high tissue levels in cases where beta-lactames or tetracyclines cannot be administered without detrimental side-effects.

Antibacterial agents in pediatrics

From low birth weight infants to adolescents, physiologic and developmental differences underlie the marked differences in pharmacokinetics and pharmacodynamics of antibacterial agents. Certain diseases, such as cystic fibrosis, also can alter these parameters. This article describes the principles of pharmacokinetics and pharmacodynamics that are unique to children and that characterize the clinical application of selected antibacterial agents to infectious diseases in children.

In-vitro and in-vivo antibiotic susceptibilities of Lyme disease Borrelia isolated in China

The antibiotic susceptibilities of seven Borrelia burgdorferi sensu lato isolates from Ixodes persulcatus in China were examined by in-vitro microdilution minimum inhibition concentration (MIC) and macrodilution minimum bactericidal concentration (MBC) methods. All isolates tested were susceptible to amoxicillin, erythromycin, and minocycline. The MICs of these drugs for the Chinese isolates were 0.025-0.1 microg/ml, <0.012-0.05 microg/ml, and <0.012-0.05 microg/ml, respectively. The MBCs were 0.1-0.39 microg/ml, <0.012-0.2 microg/ml, and 0.025-0.39 microg/ml, respectively. The in-vivo antimicrobial susceptibilities of the Chinese Borrelia isolates to two test drugs, amoxicillin and minocycline, were evaluated using ddY mice. Mice were infected by subcutaneous inoculation into the right hind footpad. When infection was confirmed, the mice were treated by subcutaneous injection of the test drugs into the back. Amoxicillin and minocycline, which possessed high in-vitro activities against Lyme disease Borrelia, provided good protection against borreliosis in this animal model. Higher doses of these drugs resulted in elimination of the Lyme disease spirochete from all animals receiving this course of treatment. The 50% curative doses (CD50) of amoxicillin and minocycline were 8.7 mg/kg and 3.1 mg/kg, respectively. This suggested that amoxicillin and minocycline could be useful for the treatment of Chinese Borrelia infection.

Comparative bacteriostatic and bactericidal activities of cefodizime against Borrelia burgdorferi sensu lato

The MIC and MSC (minimum spirocheticidal concentration) and killing rate for Borrelia burgdorferi, the etiological agent of Lyme disease, were assessed for cefodizime in comparison with ceftriaxone, minocycline, azithromycin, roxithromycin, and ciprofloxacin. The range of cefodizime MICs was greater than those of azithromycin and roxithromycin but comparable to those of ceftriaxone and minocycline. The MSCs were 1 to 2 dilutions higher than the MICs of all of the tested compounds. The killing curves of cefodizime and ceftriaxone showed parallel courses. In conclusion, cefodizime exerted an activity comparable to that of ceftriaxone against B. burgdorferi.

Dialysis culture for determination of MIC and MBC of benzylpenicillin against Borrelia burgdorferi

Minimal inhibitory concentration (MIC) of benzylpenicillin (Pen G) against strains of Borrelia burgdorferi has earlier been determined by a recently developed dialysis culture technique which provides a constant concentration of Pen G. To further investigate this method, both MIC and minimal bactericidal concentration (MBC) of Pen G against B. burgdorferi were determined and the results were compared with those obtained by other authors using different methods. The incubation period was 7 days and subcultures for MBC were observed for a further 2 weeks. The study showed results of MIC and MBC similar to those of broth microdilution, indicating sensitivity, but lower values than the majority of MIC and MBC results reported by other authors using broth macrodilution. It is essential for the results of antibiotic sensitivity testing in vitro against slowly growing bacteria like Borrelia burgdorferi that the concentration of antibiotics such as Pen G, which are unstable in solution, is constant during the incubation period.

Persistence of Borrelia burgdorferi in experimentally infected dogs after antibiotic treatment

In specific-pathogen-free dogs experimentally infected with Borrelia burgdorferi by tick exposure, treatment with high doses of amoxicillin or doxycycline for 30 days diminished but failed to eliminate persistent infection. Although joint disease was prevented or cured in five of five amoxicillin- and five of six doxycycline-treated dogs, skin punch biopsies and multiple tissues from necropsy samples remained PCR positive and B. burgdorferi was isolated from one amoxicillin- and two doxycycline-treated dogs following antibiotic treatment. In contrast, B. burgdorferi was isolated from six of six untreated infected control dogs and joint lesions were found in four of these six dogs. Serum antibody levels to B. burgdorferi in all dogs declined after antibiotic treatment. Negative antibody levels were reached in four of six doxycycline- and four of six amoxicillin-treated dogs. However, in dogs that were kept in isolation for 6 months after antibiotic treatment was discontinued, antibody levels began to rise again, presumably in response to proliferation of the surviving pool of spirochetes. Antibody levels in untreated infected control dogs remained high.

In vivo activities of ceftriaxone and vancomycin against Borrelia spp. in the mouse brain and other sites

Borrelia burgdorferi, the agent of Lyme disease, and B. turicatae, a neurotropic agent of relapsing fever, are susceptible to vancomycin in vitro, with an MIC of 0.5 microgram/ml. To determine the activity of vancomycin in vivo, particularly in the brain, we infected adult immunocompetent 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 effectiveness of treatment was assessed by cultures of blood and brain and other tissues. Ceftriaxone at a dose of 25 mg/kg of body weight administered every 12 h for 7 to 10 days eliminated cultivable B. burgdorferi or B. turicatae from all BALB/c or scid mice in the study. Vancomycin 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 delayed for 7 days or more, vancomycin failed to eradicate infection with B. burgdorferi or B. turicatae from immunodeficient mice. The failure of vancomycin in eradicating established infections in immunodeficient mice was associated with the persistence of viable spirochetes in the brain during antibiotic treatment.

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.

Concentrations of doxycycline and penicillin G in sera and cerebrospinal fluid of patients treated for neuroborreliosis

Concentrations of doxycycline and penicillin G in serum and cerebrospinal fluid (CSF) were analyzed in 46 patients during treatment for neuroborreliosis. Twenty patients were treated intravenously with penicillin G at 3 g every 6 h (q6h), and 26 patients were treated orally with doxycycline at 200 mg q24h. All samples were collected on day 13 of treatment. The median concentrations of penicillin G in serum were 0.5, 37, and 5.6 micrograms/ml before and 1 and 3 h after drug administration, and that in CSF was 0.5 (range, 0.3 to 1.6) microgram/ml after 2 to 3 h. The median concentrations of doxycycline in serum were 2.1, 6.1, and 4.7 micrograms/ml before and 2 and 6 h after drug administration, and that in CSF was 0.6 (range, 0.4 to 2.5) microgram/ml after 4 h. All patients had concentrations of penicillin G or doxycycline in CSF above the lowest reported MICs of penicillin G (0.003 microgram/ml) and doxycycline (0.12 microgram/ml) for Borrelia burgdorferi. However, no patients had a drug concentration in CSF above the highest reported MIC of penicillin G (8 micrograms/ml), and only one had a drug concentration in CSF above the highest reported MIC of doxycycline (2 micrograms/ml), despite good clinical response to treatment. No treatment failure or relapse was observed during a 1-year follow-up, although one patient treated with penicillin G and one treated with doxycycline were retreated because of residual pain. The chosen dosages of penicillin G and doxycycline seem to give sufficient concentrations in serum and CSF for the treatment of neuroborreliosis.

In vitro and in vivo antibiotic susceptibility of Lyme disease Borrelia isolated from the ixodid tick in Japan

Antimicrobial susceptibility of the Lyme disease Borrelia, strain HP1 vi, isolated from the tick ixodes persulcatus in Hokkaido, Japan, was determined in vitro and in vivo. A broth dilution technique was used to determine the minimum inhibitory concentrations (MICs) and minimum borreliacidal concentrations (MBCs) of five antimicrobial agents. Strain HP1 vi was most susceptible to minocycline (MBC, 0.2 micrograms/ml). The other antimicrobial agents tested, aspoxicillin, cefmetazole sodium, imipenem cilastatin sodium, and panipenem betamipron, had higher MBCs of 12.5 micrograms/ml, 25 micrograms/ml, > 25 micrograms/ml, and > 25 micrograms/ml, respectively. In vivo antibiotic susceptibility study using a ddY mouse model demonstrated that minocycline and amoxicillin were effective; minocycline had a lower 50% effective dose (ED50) value (6.25 mg/kg) than amoxicillin (30 mg/kg).

Comparison of cefuroxime axetil and doxycycline in treatment of patients with early Lyme disease associated with erythema migrans

A randomized, multicenter, investigator-blinded clinical trial was undertaken in order to compare the efficacies of cefuroxime axetil and doxycycline in the treatment of patients with Lyme disease associated with erythema migrans. A total of 232 patients with physician-documented erythema migrans were treated orally for 20 days with either cefuroxime axetil, 500 mg twice daily (119 patients), or doxycycline, 100 mg three times daily (113 patients), and clinical evaluations were conducted during treatment (8 to 12 days) and at 1 to 5 days and 1, 3, 6, 9, and 12 months posttreatment. Patients were assessed as to the resolution of erythema migrans and of the signs and symptoms related to early Lyme disease as well as to the prevention of late Lyme disease. A satisfactory clinical outcome (success or improvement) was achieved in 90 of 100 (90%) evaluable patients treated with cefuroxime axetil and in 89 of 94 (95%) patients treated with doxycycline (difference, -5%; 95% confidence interval, -12 to 3%). Patients with paresthesia, arthralgia, or irritability at enrollment were at higher risk for an unsatisfactory clinical outcome at 1 month posttreatment. Of the patients with satisfactory outcomes at 1 month posttreatment who were evaluable at 1 year posttreatment, a satisfactory outcome was achieved in 62 of 65 (95%) and in 53 of 53 (100%) patients treated with cefuroxime axetil and doxycycline, respectively (difference, -5%; 95% confidence interval, -10 to 4%). Twenty-eight percent of patients treated with doxycycline and 17% of those treated with cefuroxime axetil had one or more drug-related adverse events (P = 0.041). Doxycycline was associated with more photosensitivity reactions (6% compared with 0% for patients treated with cefuroxime axetil; P=0.006), and cefuroxime axetil was associated with more cases of diarrhea (5% compared with 0% for patients treated with doxycycline; P=0.030). Jarisch-Herxheimer reactions occurred in 12% of the patients in each treatment group. In summary, cefuroxime axetil is well tolerated and appears to be equally as effective as doxycycline in the treatment of early Lyme disease and in preventing the subsequent development of late Lyme disease.

Ultrastructure of Borrelia burgdorferi after exposure to benzylpenicillin

The aim of this study was to investigate the morphological changes of Borrelia burgdorferi associated with penicillin treatment. An isolate of B. burgdorferi from an erythema migrans lesion was cultivated in BSK II medium and exposed to increasing concentrations (0.0625 mg/l-2 mg/l) of penicillin G for 5 days. The in vitro minimal inhibitory concentration (MIC) was determined to be 0.5 mg/l by broth dilution method. The morphological structures of untreated spirochetes, as well as their characteristic ultrastructural changes when exposed to penicillin, were observed by electron microscopy. The following alterations were discovered: (i) Numerous outer sheath blebs at a penicillin concentration of 0.0625 mg/l. (ii) A characteristic irregular waveform of the borrelial cells and complete loss of the outer sheath at a penicillin concentration of 0.125 mg/l. (iii) The presence of "spheroplasts" at the same concentration. (iv) Structural changes of the protoplasmic cylinder complex which showed an irregular pattern at a penicillin concentration of 0.125 mg/l. (v) Disruption of the protoplasmic cylinder complex into several parts at penicillin concentrations of 0.25 mg/l and 0.5 mg/l. (vi) Severe cytolysis at penicillin concentrations of 1 mg/l and 2 mg/l.

Effectiveness of antimicrobial treatment against Borrelia burgdorferi infection in mice

Although antimicrobial agents are effective therapy for early Lyme disease, optimal treatment schedules have not been conclusively established. The efficacy of various dosages of eight antibiotics used for borreliosis treatment was evaluated for C3H/HeNCrIBR mice, which reproducibly develop persistent infection, arthritis, and carditis when inoculated with Borrelia burgdorferi. Amoxicillin-clavulanic acid, ceftriaxone, and high-dose penicillin G effectively eliminated infection and disease. Oxytetracycline, doxycycline, chloramphenicol, erythromycin, and azithromycin failed to cure infected mice. There was a correlation between peak serum antibiotic concentrations in mice, as determined by agar well diffusion bioassays, and therapeutic levels in humans. When experimentally inoculated mice were treated at 1 week postinfection with ceftriaxone (16 mg/kg of body weight twice daily for 5 days) and monitored for up to 90 days, all treated mice were free of spirochetes and had no gross or histologic lesions. This antibiotic regimen at days 7 to 11 postinoculation eliminated the spirochetes so that there were no relapses during the 90-day observation period. For experimentally inoculated mice treated with ceftriaxone at 7 or 14 days postinfection, arthritis, carditis, and infection were eliminated. When treatment began at 30 and 90 days after inoculation, infection and active cardiac and arthritic lesions were eradicated; however, residual mild synovitis and vasculitis persisted in some mice. In comparison with inoculated, untreated mice, ceftriaxone therapy at 7, 14, 30, and 90 days postinfection abrogated the development of antibody titers against B. burgdorferi. Having the potential to determine the presence of the spirochete through culture and histologic lesions makes the B. burgdorferi-inoculated C3H mouse model a valuable adjunct in evaluating chemotherapeutic options for Lyme disease.

In vitro antibiotic susceptibilities of Borrelia isolates from erythema migrans lesion of Lyme disease patients in Japan

Antibiotic susceptibilities of twelve borrelial isolates from skin of patients with erythema migrans (EM) and ticks (Ixodes persulcatus and I. ovatus) in Japan were examined by in vitro microdilution MIC method and macrodilution MBC method. Nine EM isolates and 3 tick isolates were susceptible to amoxicillin, erythromycin, and minocycline. MICs for Japanese isolates were 0.038-0.30 microgram/ml, < 0.012 microgram/ml, and < 0.012-0.05 microgram/ml, respectively. MBCs were as follows: 0.038-0.88 microgram/ml, < 0.012-0.10 microgram/ml, and < 0.025-0.78 microgram/ml, respectively. These antibiotics could be recommended for treatment of patients in early stage of Lyme disease in Japan.

Azithromycin versus penicillin V for the treatment of early Lyme borreliosis

In a randomized multicenter therapeutic trial, 32 patients with erythema migrans received oral azithromycin 500 mg once daily and 33 patients received phenoxymethylpenicillin (penicillin V) 1 million U three times daily for 10 days. Follow-up was for a median of 17 (range 3-32) months. Four weeks after initiation of therapy, 20 (62%) patients given azithromycin and 17 (51%) patients given penicillin V were completely free of all signs and symptoms and did not develop new ones subsequently (no significant difference). Three months after initiation of therapy, the corresponding figures were 25 (78%) azithromycin and 28 (85%) penicillin V recipients (no significant difference). There were only minor sequelae such as arthralgia, headache, fatigue, stiff neck and dysesthesia. Azithromycin led to a significantly faster resolution of the erythema migrans than penicillin V (p < 0.001). Significantly more patients with more severe compared with mild initial disease had an elevated IgM antibody titer prior to therapy (p < 0.001). Usually mild to moderate side effects occurred in 12 patients given azithromycin and five patients given penicillin V (p < 0.05). Azithromycin appears to be as effective as penicillin V for the treatment of early Lyme borreliosis and it seems to clear the erythema migrans more promptly.

In vitro susceptibility of Borrelia burgdorferi to 11 antimicrobial agents

The in vitro susceptibility of Borrelia burgdorferi to 11 antimicrobial agents was investigated. The antimicrobial agents evaluated included ceftizoxime, FK037, cefotaxime, dirithromycin, clarithromycin and its metabolite 14-hydroxy-clarithromycin, erythromycin, doxycycline, amoxicillin, ciprofloxacin, and ofloxacin. Isolates of B. burgdorferi tested included two reference strains (B31 and ATCC 53899), six isolates from the midwestern United States, and three from Europe. A broth macrodilution method was used to determine MICs and MBCs. B. burgdorferi was inhibited by < or = 0.5 micrograms of each of the agents except the quinolones per ml. The MBCs for 90% of strains tested of ceftizoxime, FK037, clarithromycin, 14-OH clarithromycin, and dirithromycin (< or = 1.0 microgram of each per ml) were superior to those of amoxicillin (2.0 micrograms/ml) and doxycycline (4.0 micrograms/ml). Further in vivo studies are warranted to determine whether these agents may be efficacious in the treatment of Lyme borreliosis.

The biological and social phenomenon of Lyme disease

Lyme disease, unknown in the United States two decades ago, is now the most common arthropod-borne disease in the country and has caused considerable morbidity in several suburban and rural areas. The emergence of this disease is in part the consequence of the reforestation of the northeastern United States and the rise in deer populations. Unfortunately, an accurate estimation of its importance to human and animal health has not been made because of difficulties in diagnosis and inadequate surveillance activities. Strategies for prevention of Lyme disease include vector control and vaccines.

Efficacy of clarithromycin for treatment of experimental Lyme disease in vivo

Clarithromycin provided effective therapy against arthritis induced by Borrelia burgdorferi infection in the hamster. In vitro, clarithromycin was at least 1 log more potent than tetracycline against two isolates of B. burgdorferi from human sources, as measured by MICs and 50% inhibitory concentrations. Clarithromycin was effective in preventing the onset of B. burgdorferi-induced arthritis, as determined by several parameters of paw swelling. When administered after the onset of arthritis, clarithromycin therapy reduced the degree of swelling and decreased recovery time. These results suggest that clarithromycin has potential as an effective therapy for Lyme disease.

In vitro activity of vancomycin against the spirochete Borrelia burgdorferi

Borrelia burgdorferi, a spirochete and the causative agent of Lyme disease, has been reported to be susceptible to a variety of antimicrobial agents. In this investigation, the action of vancomycin, a glycopeptide antibiotic not previously known to have activity against spirochetes, against borrelias was examined. The in vitro activity of vancomycin against a variety of strains of B. burgdorferi and one strain of Borrelia hermsii was determined by use of a microdilution MIC method (L.L. Dever, J.H. Jorgensen, and A.G. Barbour, J. Clin. Microbiol. 30:2692-2697, 1992). MICs ranged from 0.5 to 2 micrograms/ml. MICs of the glycopeptides ristocetin and teicoplanin and the lipopeptide daptomycin against strain B31 of B. burgdorferi were all > or = 8 micrograms/ml. Subsurface plating, time-kill studies, synergy studies, and electron microscopy were used to investigate further the activity of vancomycin against B31. The MBC of vancomycin was 2 micrograms/ml. Time-kill curves demonstrated > or = 3-log10-unit (99.9%) killing of the final inoculum after 72 h by vancomycin concentrations twice the MIC. Synergy between vancomycin and penicillin was demonstrated at concentrations one-fourth the MIC of each drug. In electron microscopy, B31 cells exposed to vancomycin showed a disruption of cellular integrity and were indistinguishable from those exposed to penicillin. These studies demonstrate another class of microorganisms susceptible in vitro to vancomycin.

In vitro antimicrobial susceptibility testing of Borrelia burgdorferi: a microdilution MIC method and time-kill studies

The susceptibility of Borrelia burgdorferi, the causative agent of Lyme borreliosis, to various antimicrobial agents varies widely among published studies. These differences are probably due in part to variations in susceptibility testing techniques and growth endpoint determinations. We developed a microdilution method for determining the MICs of antibiotics against B. burgdorferi. The method incorporated BSK II medium, a final inoculum of 10(6) cells per ml, and a 72-h incubation period and was found to be simple and highly reproducible. A variety of antibiotics and strains of B. burgdorferi and one strain of Borrelia hermsii were examined by this method. MICs of penicillin, ceftriaxone, and erythromycin for the B31 strain of B. burgdorferi were 0.06, 0.03, and 0.03 microgram/ml, respectively. We compared the MICs obtained by the microdilution method with those obtained by a macrodilution method using similar criteria for endpoint determinations and found the values obtained by both methods to be in close agreement. To further investigate the bactericidal activities of penicillin, ceftriaxone, and erythromycin against strain B31, we used subsurface plating to determine MBCs and we also performed time-kill studies. The MBCs of penicillin, ceftriaxone, and erythromycin were 0.125, 0.03, and 0.06 micrograms/ml, respectively. Time-kill curves demonstrated a greater than or equal to 3-log10-unit killing after 72 h with penicillin, ceftriaxone, and erythromycin; ceftriaxone provided the greatest reduction in CFU. The described methods offer a more standardized and objective approach to susceptibility testing of B. burgdorferi.

In vitro susceptibilities of Borrelia burgdorferi to five oral cephalosporins and ceftriaxone

We determined the in vitro susceptibilities of eight Borrelia burgdorferi isolates to five oral cephalosporins. MICs for B. burgdorferi 297 were 23 micrograms/ml (cephalexin), 45 micrograms/ml (cefadroxil), 91 micrograms/ml (cefaclor), 0.13 microgram/ml (cefuroxime), 0.8 microgram/ml (cefixime), and 0.02 microgram/ml (ceftriaxone). When B. burgdorferi isolates were exposed to concentrations twice the MIC of cefuroxime, cefixime, or ceftriaxone, at least 72 h of incubation was required to kill 99% of the organisms.

Treatment of early Lyme disease

PURPOSE

To compare the safety and efficacy of azithromycin, amoxicillin/probenecid, and doxycycline for the treatment of early Lyme disease, to identify risk factors for treatment failure, and to describe the serologic response in treated patients.

PATIENTS AND METHODS

Fifty-five patients with erythema migrans and two patients with flu-like symptoms alone and fourfold changes in antibody titers to Borrelia burgdorferi were randomized to receive (1) oral azithromycin, 500 mg on the first day followed by 250 mg once a day for 4 days; (2) oral amoxicillin 500 mg and probenecid 500 mg, three times a day for each for 10 days; or (3) doxcycline, 100 mg twice a day for 10 days. If symptoms were still present at 10 days, treatment was extended with amoxicillin/probenecid or doxycycline for 10 more days. Evaluations were done at study entry and 10, 30, and 180 days later.

RESULTS

Three of the patients who initially had symptoms suggestive of spread of the spirochete to the nervous system, one from each antibiotic treatment group, subsequently developed neurologic abnormalities, but symptoms in the other 54 patients resolved within 3 to 30 days after study entry. Six of the 19 patients (32%) (95% confidence interval, 13% to 57%) given amoxicillin/probenecid developed a drug eruption, whereas none of the patients given azithromycin or doxycycline had this complication. The presence of dysesthesias at study entry was the only risk factor significantly associated with treatment failure (p less than 0.001). By convalescence, 72% of the patients were seropositive, and 56% still had detectable IgM responses to the spirochete 6 months later.

CONCLUSIONS

The three antibiotic regimens tested in this study were generally effective for the treatment of early Lyme disease, but the regimens differ in the frequency of side effects and in ease of administration.