Ceftriaxone-induced neutropenia successfully overcome by a switch to penicillin G in Cardiobacterium hominis endocarditis.

Leukopenia, including agranulocytosis, is a severe complication of treatment with all β-lactam antibiotics. Its incidence increases with age. Cardiobacterium hominis endocarditis after implantation of an aortic valve bio-prosthesis in a 77-year-old woman was treated with ceftriaxone 2 g/day plus gentamicin 160 mg/day intravenously. On Day 25 of treatment, blood leukocytes had decreased to 1800/μl (neutrophils 370/μl). Antibiotic therapy was switched to penicillin G 20 million international units (IU)/day. Thereafter, blood leukocytes including neutrophils normalized suggesting that penicillin G was less bone marrow-toxic than ceftriaxone. High-dose ciprofloxacin, the alternative to penicillin G, was avoided because of the risk of cognitive and behavioral side effects. The present case suggests that with close laboratory monitoring a β-lactam with differing side chains should not be considered contraindicated after β-lactam antibiotic-induced neutropenia.