Rare Capnocytophaga sputigena bacteremia in a patient with acute lymphoblastic leukemia

Capnocytophaga sputigena, a species of bacteria resident in the human oral cavity, can rarely cause opportunistic infections in immunocompromised patients. The present case concerns a 40-year-old man with acute lymphoblastic leukemia, diagnosed in 2001, who underwent two hematopoietic stem cell transplants and had experienced relapses and remissions over nearly a 20-year period. Because his acute lymphoblastic leukemia was refractory, he was no longer receiving active treatment and was instead managed with supportive care. Under these circumstances, he developed febrile neutropenia with stomatitis, and C. sputigena was detected in blood culture. Cefepime was ineffective, but the patient's symptoms improved with tazobactam/piperacillin. The isolate was found to harbor the resistance genes Capnocytophaga sputigena β-lactamase-1 (CSP-1), cfxA3, and erm(F). The simultaneous presence of both CSP-1 and cfxA3 genes is rare. Since standard drug susceptibility testing for C. sputigenahas not yet been established, it is important to establish a standard drug susceptibility test for the appropriate treatment of C. sputigena. And physicians should consider the possibility that C. sputigena may be the causative microorganism in febrile neutropenia associated with oral mucosal injury.