DOI: 10.1093/jac/dkae071 ISSN: 0305-7453

Comparison of the in vitro activities of delafloxacin and comparators against Staphylococcus epidermidis clinical strains involved in osteoarticular infections: a CRIOGO multicentre retrospective study

E Tessier, L Ruffier d’Epenoux, M F Lartigue, L Chaufour, C Plouzeau-Jayle, R Chenouard, F Guérin, D Tandé, C Lamoureux, P Bémer, S Corvec, Pierre Abgueguen, Marin Caubrière, Carole Lemarie, Rachel Chenouard, Hélène Pailhories, Amandine Vildy, Séverine Ansart, Luc Quaesaet, Eric Stindel, Didier Tandé, Claudie Lamoureux, Anaïs Greves, David Boutoille, Raphaël Lecomte, Colin Deschanvres, Christophe Nich, Vincent Crenn, Pascale Bémer, Stéphane Corvec, Louise Ruffier d’Epenoux, Axelle Paquin, Matthieu Grégoire, Céline Bourigault, Barbara Plantard, France Cazenave-Roblot, Gwenaël Le Moal, Pierre Pries, Chloé Plouzeau-Jayle, Céline Thomas, Cédric Arvieux, Marion Baldeyrou, Harold Common, Vincent Cattoir, Sophie Reissier, Anne Méheut, Louis Bernard, Adrien Lemaignen, Marion Lacasse, Philippe Rosset, Louis-Romée Le Nail, Marie-Frédérique Lartigue, Isabelle Laplaige, Laura Chaufour,
  • Infectious Diseases
  • Pharmacology (medical)
  • Pharmacology
  • Microbiology (medical)

Abstract

Objectives

Staphylococcus epidermidis bone and joint infections (BJIs) on material are often difficult to treat. The activity of delafloxacin has not yet been studied on S. epidermidis in this context. The aim of this study was to assess its in vitro activity compared with other fluoroquinolones, against a large collection of S. epidermidis clinical strains.

Methods

We selected 538 S. epidermidis strains isolated between January 2015 and February 2023 from six French teaching hospitals. One hundred and fifty-two strains were ofloxacin susceptible and 386 were ofloxacin resistant. Identifications were performed by MS and MICs were determined using gradient concentration strips for ofloxacin, levofloxacin, moxifloxacin and delafloxacin.

Results

Ofloxacin-susceptible strains were susceptible to all fluoroquinolones. Resistant strains had higher MICs of all fluoroquinolones. Strains resistant to ofloxacin (89.1%) still showed susceptibility to delafloxacin when using the Staphylococcus aureus 2021 CA-SFM/EUCAST threshold of 0.25 mg/L. In contrast, only 3.9% of the ofloxacin-resistant strains remained susceptible to delafloxacin with the 0.016 mg/L S. aureus breakpoint according to CA-SFM/EUCAST guidelines in 2022. The MIC50 was 0.094 mg/L and the MIC90 was 0.38 mg/L.

Conclusions

We showed low delafloxacin MICs for ofloxacin-susceptible S. epidermidis strains and a double population for ofloxacin-resistant strains. Despite the absence of breakpoints for S. epidermidis, delafloxacin may be an option for the treatment of complex BJI, including strains with MICs of ≤0.094 mg/L, leading to 64% susceptibility. This study underlines the importance for determining specific S. epidermidis delafloxacin breakpoints for the management of BJI on material.

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