Capnocytophaga sputigena bacteremia in a nasopharyngeal carcinoma patient with severe neutropenia: a case report

Capnocytophaga sputigena, a fastidious Gram-negative commensal of the human oral flora, rarely causes bloodstream infections but poses significant risks to immunocompromised hosts, particularly those with hematologic malignancies or mucosal barrier injury. We report a rare case of C. sputigena bacteremia in a 51-year-old man with epidermal growth factor receptor (EGFR)-positive nasopharyngeal carcinoma (NPC) Stage IV (cT3N2M1), as confirmed by immunohistochemistry. The patient, who was undergoing chemotherapy, presented with severe neutropenia (absolute neutrophil count 0.04 × 109/L), fever (38.9°C), and oral mucositis. Blood cultures identified slender Gram-negative bacilli, which were confirmed as C. sputigena using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and 16S rDNA sequencing. Initial empirical therapy with meropenem led to clinical improvement, and antimicrobial therapy was subsequently de-escalated to ceftazidime. The patient was eventually discharged in stable condition. This case underscores that C. sputigena can act as an opportunistic pathogen in solid tumor patients with therapy-induced mucosal damage and highlights the critical importance of meticulous oral care and advanced microbiological diagnostics in managing immunocompromised individuals.