In vitro susceptibility of Cutibacterium acnes to dalbavancin: comparison between gradient test and the agar dilution reference method.
4 affiliations
- 1School of Medical Sciences, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
- 2Department of Orthopedics, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
- 3Department of Laboratory Medicine, WHO Collaborating Centre for Gonorrhoea and Other STIs, National Reference Laboratory for STIs, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
- 4EUCAST Development Laboratory, Clinical Microbiology, Växjö Hospital, Växjö, Sweden.
Abstract
Background
Cutibacterium acnes, a human commensal, occasionally causes infections requiring long-term antibiotic treatment, including periprosthetic joint infections. Dalbavancin is a new lipoglycopeptide that allows intermittent dosing because of its exceptionally long half-life. However, data on susceptibility of C. acnes to dalbavancin are lacking, and no EUCAST breakpoints have been defined.Objectives
To determine the MIC distribution of C. acnes for dalbavancin, and to compare the gradient test to the agar dilution reference method.Methods
C. acnes isolates were obtained from tissue samples from arthroplasties (n = 117), skin samples (n = 15), and positive blood cultures (n = 85). Antibiotic susceptibility was tested by agar dilution according to EUCAST methodology for anaerobic bacteria (±polysorbate 80) and by gradient test.Results
MIC50 and MIC90 for dalbavancin against C. acnes were 0.03 and 0.06 mg/L using agar dilution, and 0.004 and 0.008 mg/L with the gradient test. The gradient test yielded 3-fold lower MIC values than agar dilution. No significant difference was observed when polysorbate 80 was added to the agar dilution test. When vancomycin was tested as a comparator, the MICs did not differ between the agar dilution and gradient tests; MIC50 and MIC90 were 0.5 mg/L in both tests.Conclusions
C. acnes showed significantly lower MIC values for dalbavancin than for vancomycin, highlighting the potential of dalbavancin as a therapeutic option. The gradient test yielded significantly lower MICs for dalbavancin than the reference method for anaerobes, agar dilution, suggesting that the gradient test for dalbavancin may not be a reliable method for antibiotic susceptibility testing (AST) of C. acnes.
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BibTeX
@article{svensson2026vitro,
title = {{In vitro susceptibility of Cutibacterium acnes to dalbavancin: comparison between gradient test and the agar dilution reference method.}},
author = {Sara Svensson and Susanne Jacobsson and Erika Matuschek and Bo Söderquist},
journal = {The Journal of antimicrobial chemotherapy},
year = {2026},
month = oct,
doi = {10.1093/jac/dkag364},
url = {https://europepmc.org/article/MED/42910528},
note = {CC BY},
}
RIS
TY - JOUR
TI - In vitro susceptibility of Cutibacterium acnes to dalbavancin: comparison between gradient test and the agar dilution reference method.
AU - Sara Svensson
AU - Susanne Jacobsson
AU - Erika Matuschek
AU - Bo Söderquist
PY - 2026
DA - 2026/10/01
JO - The Journal of antimicrobial chemotherapy
DO - 10.1093/jac/dkag364
UR - https://europepmc.org/article/MED/42910528
AB - Background Cutibacterium acnes, a human commensal, occasionally causes infections requiring long-term antibiotic treatment, including periprosthetic joint infections. Dalbavancin is a new lipoglycopeptide that allows intermittent dosing because of its exceptionally long half-life. However, data on susceptibility of C. acnes to dalbavancin are lacking, and no EUCAST breakpoints have been defined.Objectives To determine the MIC distribution of C. acnes for dalbavancin, and to compare the gradient test to the agar dilution reference method.Methods C. acnes isolates were obtained from tissue samples from arthroplasties (n = 117), skin samples (n = 15), and positive blood cultures (n = 85). Antibiotic susceptibility was tested by agar dilution according to EUCAST methodology for anaerobic bacteria (±polysorbate 80) and by gradient test.Results MIC50 and MIC90 for dalbavancin against C. acnes were 0.03 and 0.06 mg/L using agar dilution, and 0.004 and 0.008 mg/L with the gradient test. The gradient test yielded 3-fold lower MIC values than agar dilution. No significant difference was observed when polysorbate 80 was added to the agar dilution test. When vancomycin was tested as a comparator, the MICs did not differ between the agar dilution and gradient tests; MIC50 and MIC90 were 0.5 mg/L in both tests.Conclusions C. acnes showed significantly lower MIC values for dalbavancin than for vancomycin, highlighting the potential of dalbavancin as a therapeutic option. The gradient test yielded significantly lower MICs for dalbavancin than the reference method for anaerobes, agar dilution, suggesting that the gradient test for dalbavancin may not be a reliable method for antibiotic susceptibility testing (AST) of C. acnes.
SN - 0305-7453
SN - 1460-2091
ER -