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.