Hyperammonemia syndrome due to Pluralibacter gergoviae bacteremia in an immunocompromised patient: case report

Pluralibacter gergoviae is a rare, opportunistic, urease-producing gram-negative organism infrequently implicated in invasive infections. Reports in organ transplant or extracorporeal membrane oxygenation (ECMO) settings are exceedingly uncommon. This case is distinctive for describing P. gergoviae bacteremia potentially associated with severe hyperammonemia and encephalopathy in a lung transplant recipient on prolonged ECMO support, expanding the clinical spectrum of infection-related hyperammonemia beyond the traditionally recognized Ureaplasma and Mycoplasma species.

A 32-year-old woman with cystic fibrosis underwent bilateral lung transplantation while on ECMO for refractory hypoxemic respiratory failure. Her post-operative course was complicated by multiorgan failure, Candida parapsilosis fungemia, and later, surgical site infection. During the fourth month of hospitalization, P. gergoviae was isolated from surgical wound and blood cultures. Around the time of bacteremia, she developed acute encephalopathy with markedly elevated plasma ammonia (262 µmol/L) in the absence of hepatic dysfunction. The P. gergoviae isolate was confirmed to be urease positive. Management included targeted antimicrobial therapy with ceftriaxone and meropenem, along with lactulose, rifaximin, and zinc for hyperammonemia. Ammonia levels and mental status gradually normalized following treatment, and blood cultures cleared.

This case illustrates P. gergoviae as an emerging opportunistic pathogen capable of causing invasive infection and possibly metabolic complications in profoundly immunocompromised hosts.