Abstract
Pet ownership is common in the United States, with 38.4% of households owning dogs, according to the American Veterinary Medical Association. Zoonotic infections are rare, but can cause serious disease, particularly in immunocompromised hosts. Capnocytophaga species are gram-negative, facultative anaerobic bacteria that are usually transmitted to humans from dogs but may also be human oral cavity commensals. They can cause rare but fulminant infections with a mortality rate of 10-30%. We report a case of capnocytophaga in a lung transplant recipient (LTR).
A 72-year-old LTR on a standard immunosuppressive regimen with tacrolimus, mycophenolate mofetil, and prednisone reported right-sided back pain 2 years after transplantation. Computed tomography (CT) revealed a moderate right pleural effusion without lung parenchymal abnormalities. Pleural studies were exudative with an LDH of 740 units/L, total protein of 2.7 g/dL, and glucose of 89 mg/dL. All pleural fluid cultures were negative. His serum procalcitonin was marginally elevated at 0.2 ng/mL and his white blood cell count was normal (4.0 thousand/uL). He was subsequently hospitalized, underwent bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsies, and was empirically treated with high-dose corticosteroids for presumed acute cellular rejection. The day after hospital discharge, capnocytophaga grew in BAL fluid cultures. He was readmitted to the hospital for chest tube drainage, intrapleural tissue plasminogen activator infusion to break up loculations, and a 4-week course of ceftriaxone. With antimicrobial therapy, the patient recovered clinically; however, his right lung remained trapped and a thick pleural rind was identified on CT. Upon further history, the patient and his wife reported owning 2 Pekingese-Poodle mix dogs; however, they were meticulous about avoiding contact with the dogs’ saliva.
Capnocytophaga infection in LTRs is rare, but due to its propensity to result in severe disease among immunosuppressed patients, accurate identification and prompt treatment is required. Transplant recipients need to be counseled regarding risk of contracting zoonotic infections from household pets so they can take appropriate preventative measures. However, despite best efforts, as in the case of this patient, these infections can still occur.