DELAFLOXACIN/RIFAMPICIN COMBINATION AND DAIR SURGERY DURING PROSTHETIC JOINT INFECTION: IMPORTANCE OF LOW DELAFLOXACIN MINIMAL INHIBITORY CONCENTRATION TO AVOID FAILURE

Aim S. epidermidis SE and S. haemolyticus SH are commensal bacteria from skin microbiota. Both species are involved in device-related infections, especially hip, knee or shoulder bone and joint infections. Recently, a multidrug-resistant SE clone has been reported in prosthesis infections. The aim of this study was to report three cases of SE or SH infections treated by debridement antibiotic and implant retention (DAIR) surgery and combination of delafloxacin (DFX)/rifampicin. Method Three patients were involved. Medical characteristic of the patients, the type of surgery, and the bacteria implicated were recovered. Resistance profiles and treatment with the follow up were analyzed. Results Two males and one female aged from 51, 64 and 74 y-old were selected according to the treatment. No history of prosthetic joint infection before was reported. A DAIR procedure was performed on 1 elbow and 2 hips. BMIs were normal. ASA scores were < 3. Fever was present for 2 patients and fistula for 1. No acute blood-borne infection was reported. The median time between symptom onset and surgical procedure were 5, 22 and 55 days. During the DAIR surgery, 2/4, 3/6 and 2/5 peroperative samples were positive. Two patients were infected with SE including a mixed morphotype for 1 patient and the last one was infected with SH. All strains were methicillin-resistant and levofloxacin-resistant. Delafloxacin MICs were 0.047, 0.094 and 0.125 and 0.25 mg/L. All patients were treated by delafloxacin (450 mg*2 per day) and rifampicin (600 or 900 mg per day). No adverse event was reported. Conclusions DFX MIC should be tested according to EUCAST guidelines including if strain are levofloxacin-resistant. According to EUCAST guidelines, 2 breakpoints are available. All strains were considered susceptible and a favorable outcome was noticed for two patients after a one year follow up. However, for the third patient, the one with two S. epidermidis morphotypes, a relapse was observed 1 year after the first revised surgery revealing only the less DFX susceptible SE stain (MIC 0.25 mg/L) suggesting a selection of the strain with the higher DFX MIC leading to a treatment failure. Pulsed-field gel electrophoresis analysis confirmed the genetic link between the isolates. Therefore, DFX treatment can be a therapeutic option in bone and joint infection, even for levofloxacin-resistant strain, only if the DFX MIC is less than 0.094 mg/L (Tessier et al. Journal of Antimicrobial Chemotherapy 2024).