Bacteriostatic and Bactericidal Effect of Tigecycline on Leptospira spp

Tigecycline is a relatively new antimicrobial, belonging to glycylcyclines with antimicrobial activity against a large spectrum of bacteria. Very few data are available on its effect onLeptospiraspp., which consist in a bacteriostatic mechanism. The aim of this investigation was to evaluate the bacteriostatic and bactericidal effect of tigecycline on referenceLeptospirastrains belonging to 16 serovars. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined through the microdilutions method, and tetracycline was used as the control. Results showed that tigecycline had higher MIC and MBC values than tetracycline. Obtained MIC values were between 4 and 32 mu g/mL, while MBC values between 16 and >128 mu g/mL. Patoc (MIC: 4 mu g/mL; MBC: 16 mu g/mL) resulted in the most susceptible serovar, while the most resistant were Bataviae (MIC: 32 mu g/mL; MBC: 64 mu g/mL), Bratislava (MIC: 8 mu g/mL; MBC 128 mu g/mL), and Tarassovi (MIC: 8 mu g/mL; MBC: >128 mu g/mL). This is the first investigation focused on the effect of tigecycline againstLeptospiraspp. reference strains. Since tigecycline is used as a treatment for bacteremia and urinary tract disease, and these symptoms could be linked toLeptospirainfection, the possibility of using this antibiotic as a treatment for leptospirosis should be evaluated. Further studies are needed to explore the possibility to use tigecycline for in vivo application againstLeptospira.