Intravenous fosfomycin as salvage therapy for osteomyelitis caused by multidrug-resistant Pseudomonas aeruginosa

Purpose. A case of osteomyelitis caused by multidrug-resistant (MDR) Pseudomonas aeruginosa is reported. Summary. An 84-year-old Caucasian male with an underlying history of type 2 diabetes, peripheral vascular disease, and coronary artery disease had chronic nonhealing wounds on his right foot. Wound care and a course of intravenous (IV) ertapenem with oral ciprofloxacin were ineffective. His initial wound culture grew Staphylococcus aureus, group G streptococcus and P. aeruginosa; the Pseudomonas was susceptible to multiple agents. The patient eventually required midtarsal amputation and angioplasties to his right leg. Twenty days after the operation, 2 openings were discovered at the surgical site, 1 of which was probed to the bone. He was readmitted 5 weeks after the operation. A repeat wound swab grew MDR P. aeruginosa and Finegoldia magna. The Pseudomonas was susceptible to gentamicin and colistin. The patient had revision of the infected amputation site with the goal of salvaging his right lower limb. The patient developed acute renal failure after 26 days of IV gentamicin, IV ceftriaxone, and oral metronidazole. Additional susceptibility testing was performed to identify alternatives. The bacteria were considered susceptible to IV fosfomycin, the last resort, by our microbiology laboratory. This was combined with ceftolozane/tazobactam followed by meropenem to treat the residual infection. After 2 weeks of IV fosfomycin, the patient's wound improved and further amputation was avoided. Conclusion. Our case demonstrates that IV fosfomycin may provide an effective salvage therapy when combined with beta-lactams for the treatment of severe diabetic foot infection or osteomyelitis caused by MDR P. aeruginosa.