In vitro Superiority of Teicoplanin Over Vancomycin in Clinical Isolates of Enterococcus species.

BACKGROUND

Enterococci are clinically important pathogens exhibiting intrinsic and acquired resistance to multiple antimicrobial classes. Vancomycin (VCM) and teicoplanin (TEIC) are glycopeptide antibiotics used in cases of β-lactam intolerance or resistance, yet TEIC is less frequently recommended in the guidelines despite its favorable safety profile. This study aimed to compare the in vitro activity of VCM and TEIC against clinical Enterococcus isolates by analyzing minimum inhibitory concentration (MIC) distributions.

METHODS

Between July 2024 and March 2025, 552 Enterococcus isolates were collected at Okayama University Hospital. MICs were determined using the microdilution method.

RESULTS

Among the 551 isolates, 370 (67%) were E. faecalis, 117 (21%) were E. faecium, 31 (6%) were E. avium, 21 (4%) were E. casseliflavus, and 12 (2%) were E. gallinarum. Cumulative MIC distributions revealed notably lower MICs for TEIC compared to VCM in Enterococcus faecalis, Enterococcus casseliflavus, and Enterococcus gallinarum, while Enterococcus faecium and Enterococcus avium showed comparatively equivalent MIC profiles. Particularly, the MIC50 and MIC90 values for VCM in E. faecalis (1 and 2 µg/mL, respectively) were substantially higher than those for TEIC (0.125 and 0.25 µg/mL), which remained considerably below the established antimicrobial susceptibility breakpoint. The MIC50 and MIC90 values of VCM against E. faecium were both 1 µg/mL, whereas those of TEIC were 0.5 µg/mL and 1 µg/mL, respectively.

CONCLUSIONS

These findings suggest TEIC may provide a therapeutic advantage in the management of selected enterococcal infections. Further clinical investigations to validate its role in treatment strategies for enterococcal infections are warranted.