Therapeutic drug monitoring-guided linezolid salvage therapy for Lacticaseibacillus paracasei infective endocarditis: A case report.

We report a rare case of infective endocarditis (IE) caused by Lacticaseibacillus paracasei (formerly Lactobacillus paracasei) that was managed with intravenous linezolid as salvage therapy. A 38-year-old woman presented with a three-week history of intermittent fever and cutaneous manifestations, and was diagnosed with IE caused by Lacticaseibacillus paracasei. The initial ampicillin/clindamycin therapy was discontinued due to suspected drug fever, and subsequent levofloxacin monotherapy was complicated by a drug-induced rash. Linezolid monotherapy was therefore initiated as salvage therapy, with dosing carefully adjusted via therapeutic drug monitoring (TDM) to maintain trough levels between 2 and 8 μg/mL. This approach enabled prolonged treatment without significant adverse effects, including thrombocytopenia. To our knowledge, reports of Lactobacillus IE managed with linezolid TDM are ecseedingly rare. This case suggests that linezolid, guided by TDM, may be considered as a salvage option for Lactobacillus IE.