Antimicrobial therapy using vancomycin and therapeutic drug monitoring (TDM) in patient with bacteremia caused by Arthrobacter woluwensis:a case report.

Background: Arthrobacter woluwensis (A.woluwensis) is gram-positive rod that is endemic to natural environments such as soil, but reports of infections caused by this species are limited, and effective treatment methods have not been established.

Case presentation: An 89-year-old man was hospitalized for dysmobility due to anorexia and was started on peripheral intravenous nutrition. He had a fever of 39.5 °C, shivering, and hypotension. Gram-positive rods were detected in two sets of blood cultures. The treatment using vancomycin (VCM) was started due to suspicion of catheter-related bloodstream infection. The organism was identified as A.woluwensis by MALDI-TOF MS. The MIC₅₀ for VCM was 2 µg/mL. Treatment was continued with the goal of achieving an area under the concentration-time curve (AUC) of ≥ 400 µg·h/mL, which is an indicator of the efficacy and safety of VCM in treating MRSA infection. The fever resolved after starting treatment, and the patient's condition stabilized. Further blood cultures became negative, a transthoracic echocardiogram confirmed the exclusion of infective endocarditis, and the treatment was completed after 14 days.

Conclusions: This is the first case report using VCM for the treatment and therapeutic drug monitoring (TDM) of A. woluwensis bacteremia. Our results will provide useful information for appropriate infection treatment.