Imipenem plus Fosfomycin as Salvage Therapy for Vertebral Osteomyelitis.

We applied combination antibiotic therapy to treat vertebral osteomyelitis and a psoas abscess caused by glycopeptide-intermediate (MIC, 2 µg/ml) and daptomycin-nonsusceptible (>2 µg/ml) methicillin-resistant Staphylococcus aureus The Etest synergy test showed the largest synergistic effects for imipenem/cilastatin and fosfomycin. Whole-gene sequencing showed amino acid changes in SA0802, SA1193 (mprF), and SA1531 (ald). Four weeks of combination treatment using imipenem/cilastatin (1.5 g per day) and fosfomycin (4.0 g per day) resulted in clinical improvement.