In Vitro Activity of Novel Antibiotics Against Corynebacterium spp. Clinical Isolates Responsible for Difficult-to-Treat Infections

Corynebacterium species can be responsible for difficult-to-treat (DTT) infections, for which novel therapeutic options may be used. This study assessed the in vitro activity of newer antibiotics against Corynebacterium clinical isolates responsible for DTT infections between 2021 and 2023 in our center. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution method or the gradient diffusion method. Interpretation was done according to the 2024 Comité de l'Antibiogramme de la Société Française de Microbiologie breakpoints. In total, 116 isolates were collected, including 73 (66%) responsible for bone and joint infections, among which half were device related. C. striatum was the most frequently isolated species. The activity of ceftaroline (MIC90 >2 mg/L), ceftobiprole (MIC90 >8 mg/L), and delafloxacin (MIC90 >1 mg/L) was limited. By contrast, other molecules tested showed higher activity with low MIC90 values: linezolid (MIC90 ≤0.5 mg/L), tedizolid (MIC90 = 0.12 mg/L), dalbavancin (MIC90 = 0.12 mg/L), tigecycline (MIC90 = 0.12 mg/L), eravacycline (MIC90 = 0.06 mg/L), and omadacycline (MIC90 = 0.5 mg/L). One C. striatum strain exhibited a high level of daptomycin resistance after antibiotic exposure (MIC >16 mg/L). The in vitro activity of most of these novel antibiotics is excellent against Corynebacterium clinical isolates. They could represent a real alternative for treating DTT infections due to Corynebacterium spp.