In vitro susceptibility testing of Borrelia burgdorferi by a dialysis culture method

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.

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.