Time-kill curves of daptomycin and Monte Carlo simulation for the treatment of bacteraemia caused by Enterococcus faecium

Stability of Daptomycin in Dextrose and Icodextrin-Based Peritoneal Dialysis Solutions

Background: With emerging antibiotic resistance, many patients on peritoneal dialysis require newer antibiotic treatment such as daptomycin. Inadequate clinical information exists across different peritoneal dialysis solutions, including icodextrin, for the stability of intraperitoneal daptomycin. To guide the clinical practice of intraperitoneal daptomycin treatment, we need to establish the stability of daptomycin at dextrose concentration higher than 1.5% and icodextrin, as well as the duration of stability. Methods: We tested the stability of daptomycin in three types of peritoneal dialysis bags (UltraBag dextrose 2.5%, UltraBag icodextrin 7.5%, and Stay-Safe Balance 2.3%). Daptomycin was reconstituted with water for injection (50 mg/mL), followed by administration to peritoneal dialysis bags to obtain the final daptomycin concentrations of 70 μg/mL (equivalent to 140 mg/2L, the maintenance level) and 245 μg/mL (equivalent to 490 mg/2L, the loading level). The bags were then placed at ambient temperature (25°C) followed by withdrawing 5 mL samples at 0, 4, 8, 12, 24, and 48 h for UltraBag dextrose 2.5% and UltraBag icodextrin 7.5% and 0, 4, 8, 12, and 24 h for Stay-Safe Balance 2.3%. The concentrations of daptomycin in the collected samples were quantified by high-performance liquid chromatography with diode array detector (HPLC-DAD). Results: Under ambient condition, daptomycin was stable at maintenance level in UltraBag dextrose 2.5% for 48 h and in UltraBag icodextrin 7.5% or Stay-Safe Balance 2.3% for 24 h. For loading level, daptomycin was stable in UltraBag dextrose 2.5% and Stay-Safe Balance 2.3% for 12 h and in UltraBag icodextrin 7.5% for 48 h. Conclusions: Current stability results support and guide the use of intraperitoneal daptomycin in different dialysis solutions. Patients with peritonitis requiring icodextrin exchange and assisted preparation of daptomycin can benefit from nurses who provide daily home visit based on our stability results.

In Vitro Evaluation of the Antibacterial Properties of Tea Tree Oil on Planktonic and Biofilm-Forming Streptococcus mutans

Streptococcus mutans (S. mutans) is the principal etiologic agent in the occurrence of human dental caries and the formation of biofilms on the surface of teeth. Tea tree oil (TTO) has been demonstrated to exhibit a wide range of pharmacological actions that can effectively inhibit the activity of bacteria. In this context, we evaluated the in vitro antimicrobial effects of TTO on S. mutans both during planktonic growth and in biofilms compared with 0.2% CHX. We determined the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) using the microdilution method, the bacteriostatic rate using an MTT assay, and the antimicrobial time using a time-kill assay. Then, we explored the effects of TTO on acid production and cell integrity. Furthermore, the effects of TTO on the biomass and bacterial activity of S. mutans biofilms were studied. Finally, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to investigate the structure and activity of biofilms. The MIC and MBC values were 0.125% and 0.25%, and the bacterial inhibition rate was concentration dependent. TTO can effectively inhibit bacterial acid production and destroy the integrity of the cell membrane. Electron micrographs revealed a reduction in bacterial aggregation, inhibited biofilm formation, and reduced biofilm thickness. The effect of TTO was the same as that of 0.2% CHX at a specific concentration. In summary, we suggest that TTO is a potential anticariogenic agent that can be used against S. mutans.

Daptomycin in the treatment of enterococcal bloodstream infections and endocarditis: a EUCAST position paper

SCOPE

This position paper describes the view adopted by EUCAST on the role of daptomycin in the treatment of serious infections caused by Enterococcus species.

BACKGROUND

High-dose daptomycin is considered effective in the treatment of enterococcal bloodstream infection (BSI) and endocarditis, although published clinical experience with the latter condition is limited.

METHODS

EUCAST reviewed the available published data on pharmacokinetics-pharmacodynamics (PK-PD), resistance selection, clinical efficacy and safety for the use of 10-12 mg/kg/day of daptomycin for these conditions, noting that the doses licensed by the European Medicines Agency are only 4-6 mg/kg/day, and only for infections caused by Staphylococcus aureus.

FINDINGS AND RECOMMENDATIONS

The PK-PD evidence shows that, even with doses of 10-12 mg/kg/day, it is not possible to treat infections caused by isolates at the upper end of the wild-type distributions of Enterococcus faecalis (with MICs of 4 mg/L) and E. faecium (with MICs of 4 or 8 mg/L). For this reason, and because there are ongoing issues with the reliability of laboratory testing, EUCAST lists daptomycin breakpoints for Enterococcus species as "IE"-insufficient evidence. EUCAST advises increased vigilance in the use of high-dose of daptomycin to treat enterococcal BSI and endocarditis. Additional PK-PD studies and prospective efficacy and safety studies of serious Enterococcal infections treated with high-dose daptomycin may permit the setting of breakpoints in the future.