S3285 A Rare Case of Pyogenic Liver Abscess Caused by Raoultella ornithinolytica

Abstract

Introduction: Patients with a history of splenectomy have a higher prevalence of infections with encapsulated organisms due to decreased phagocytic activity and humoral response. One such rare organism is Raoultella ornithinolytica, a Gram-negative bacillus commonly found in the aquatic environment. Here we present a rare case of this bacterium causing liver abscess. Case Description/Methods: A 72-year-old female with a history of hypertension, hyperlipidemia, and splenectomy (secondary to abdominal trauma) presented after being found down. She complained of a recent history of diarrhea 2 days ago. Blood pressure was 80/60 mmHg and temperature was 101 degrees F at presentation. She was found to have elevated liver enzymes and Klebsiella oxytoca bacteremia (found on Verigene multiplex PCR testing) and was started on broad-spectrum antibiotics. CT of the abdomen in the emergency room revealed a 3x2x5 cm hypodense lesion in the left lobe of the liver. She underwent ultrasound-guided removal of 35 cc dark brown colored fluid, which was positive by culture for Raoultella ornithinolytica. Her antibiotics were narrowed to cefazolin, and the infection was thought to be related to recent diarrhea (of unknown etiology) resulting in intestinal mucosal damage leading to translocation of the bacterium across the intestinal wall into the liver. Of note, on high specificity microbiological testing using matrix assisted desorption-time of flight (MALDI-Tof) technology, the organism recovered from the blood was confirmed to be Raoultella ornithinolytica. Discussion: Incidence of Raoultella ornithinolytica infection has been on the rise in the past decade, and our patient is the second reported case of Raoultella ornithinolytica liver abscess. In humans, it usually causes skin flushing, vomiting, diarrhea, and headache. While the first case, as reported by Surani et al in 2020, had a long-standing liver cyst that was thought to be infected with Raoultella ornithinolytica, our patient did not have any nidus in the liver that could harbor this bacterium. However, she had a history of splenectomy, possibly putting her at higher risk of infection with encapsulated bacteria. In addition, Raoultella ornithinolytica is closely related to Klebsiella oxytoca, but is not recognized in the multiplex PCR database which accounts for the discrepancy in initial identification as seen in our case. Our case adds to the growing literature regarding Raoultella ornithinolytica as an increasing virulent pathogen in humans.