Ceftaroline in the treatment of concomitant methicillin-resistant and daptomycin-non-susceptible Staphylococcus aureus infective endocarditis and osteomyelitis: case report

Sir, A middle-aged male presented to the emergency department with fever and 1 week of sharp right hip pain worsening over the past 2 days. His past medical history included uncontrolled diabetes and chronic active hepatitis C. The patient also had a history of multiple methicillin-resistant Staphylococcus aureus (MRSA) infections, including bacteraemia 1 month prior, for which he was treated with vancomycin (MIC ≤0.5–1 mg/L). Three sets of blood cultures were collected before the patient received a single dose of vancomycin and piperacillin/tazobactam. The blood Gram stain showed Gram-positive cocci. The infectious diseases team was consulted, and given recent vancomycin treatment and recurrent bacteraemia, we recommended high-dose daptomycin (8 mg/kg intravenously every 24 h). Dual therapy with rifampicin was considered, but due to limited in vivo data as well as concomitant hepatic dysfunction, we decided against it. Initial blood cultures grew MRSA (3/3 bottles) on hospital day 3, with susceptibility tests showing a daptomycin MIC of 0.38 mg/L (Etest; AB Biodisk, Solna, Sweden) and a vancomycin MIC of 1 mg/L by broth microdilution. Repeat blood cultures on day 4 (2/2 bottles) showed no growth. On hospital day 2, a transoesophageal echocardiogram (TEE) demonstrated no evidence of vegetations. On day 3, a contrast CT of the hip showed bone and retroperitoneal abscesses along with evidence highly suggestive of osteomyelitis. An MRI was less conclusive about the presence of early osteomyelitis. The surgical team was consulted and recommended that the patient to undergo CT-guided drainage of the retroperitoneal abscess as opposed to any surgical treatment, citing difficult surgical access, a high-risk patient with comorbidities and likelihood of the abnormal synovium in radiographic studies being reactive synovitis as opposed to osteomyelitis and septic arthritis. Drainage proceeded on day 7, though there was continued debate about the diagnosis and need for surgical intervention. Research letters