Volume 21, Number 7—July 2015
Oligella ureolytica Bacteremia in Elderly Woman, United States
To the Editor: Oligella ureolytica is an aerobic gram-negative coccobacillus found as a commensal organism in human urinary tracts (1). Previously referred to as CDC Group IVe, this bacterium is not commonly encountered as a source of infection and is difficult to isolate by using conventional laboratory procedures (2). The few cases of pathogenic infection with O. ureolytica described in the literature have occurred in patients ranging in age from newborn to 89 years and from the varied locations of India, Turkey, Canada, and the United States (3–7). We report a case of O. ureolytica bacteremia in a patient in whom sepsis was diagnosed and review the current literature on this emerging pathogen.
A 66-year-old woman sought treatment in our emergency department for a fever of 100.7°F, femur fracture, and a right buttock stage III decubitus ulcer. She reported having fallen 4 days earlier, after which she was unable to walk and spent 4 days laying in her own urine and feces. Blood tests revealed an elevated leukocyte count of 24.4 × 109 cells/L (76% neutrophils, 2% bands), and urinalysis showed trace leukocyte esterase, +3 bacteria, and 5–10 leukocytes. Chest radiograph and head computed tomography images were unremarkable. Her electrocardiogram showed nonspecific ST wave changes. Samples from the patient’s blood, urine, and wounds were collected while the patient was in the emergency department and were sent for culture.
Wound cultures showed growth of Proteus mirabilis and Enterococcus spp. The urine culture grew >100,000 CFU Escherichia coli. The first set of blood cultures grew O. ureolytica in aerobic and anaerobic bottles, but another set drawn 30 min later showed no growth. The blood cultures were processed by using the Bact/Alert 3D (bioMérieux, Marcy l’Etoile, France) and Gram stained. Identification was from the Vitek 2 compact system (bioMérieux). The O. ureolytica sample was sensitive to amikacin, ampicillin/sulbactam, ceftazidime, ceftriaxone, gentamicin, imipenem, levofloxacin, nitrofurantoin, trimethoprim/sulfamethoxazole, and chloramphenicol. No resistance was found.
Because of the unique bacteremia, further diagnostics were conducted. The results of chest, abdomen, and pelvic computed tomography scans were unremarkable. HIV test results were negative. The nonspecific electrocardiogram changes prompted us to request a transesophageal echocardiogram, but the patient refused. For 10 days, the patient was given vancomycin (1 g/d), aztreonam (2 g/8 h), and metronidazole (500 mg/8 h). Cultures of blood that had been collected 5 and 8 days after the original culture were sterile. After 16 days, leukocytosis and fever had resolved, and the patient was discharged to a skilled nursing facility. Although we found no reports in the literature of endocarditis caused by O. ureolytica, the patient’s refusal of a transesophageal echocardiogram and the presence of the uncommon bacterium led us to empirically continue aztreonam for endocarditis after her discharge.
The literature reports 5 cases of pathogenic O. ureolytica infection (Table). This bacterium has also been isolated from the respiratory tract of patients with cystic fibrosis (9). A 2-year study conducted in 1983 at a high-volume hospital in the United States demonstrated O. ureolytica growth in the urine of 72 patients (8). Of these patients, 71 had long-term urinary drainage systems and 14 had symptomatic urinary tract infections. Many of these patients were permanently disabled from spinal cord injuries (8). This study was the only one we found focused on O. ureolytica infection in the clinical setting. We found no cases in which a patient’s death was attributed to O. ureolytica infection, and all reported cases resolved with antimicrobial drug treatment (3–8). The low virulence of this organism may contribute to the paucity of recognized cases.
Of the reported cases, all occurred as opportunistic infections in patients with a source of immunosuppression such as malignancy, HIV, or newborn status. The patient we reported in this article showed no evidence of malignancy and had no major source of immunosuppression besides malnutrition, tobacco use, and advanced age. The patient’s wound had been contaminated by urine and feces, which was postulated to be the cause of bacteremia in the 1993 case.
Limitations in commonly available laboratory procedures make the identification of this bacterium difficult. The incubation period is long (4 days), and not all laboratories incubate cultures for that long, as occurred in the 2013 urinary tract infection case (1,3,5). Also, the identification of less commonly encountered bacteria is not always pursued to the genus and species level (2). Furthermore, it is believed that Oligella spp. can be misidentified as phenotypically similar organisms, such as Bordetella bronchiseptica and Achromobacter spp. (4,10).
We believe that many cases of O. ureolytica infection have gone unrecognized or were incorrectly identified. Some cases may also have been dismissed as contamination because of laboratorians’ and clinicians’ lack of familiarity with this bacterium. Our review suggests that advancing laboratory techniques will lead to more recognized cases and that further studies are necessary to understand this bacterium’s clinical significance.
Special thanks to Rani Bright and the Philadelphia College of Osteopathic Medicine library staff for their time, effort, and guidance in working on this manuscript.
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Table of Contents – Volume 21, Number 7—July 2015
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Tristan Simmons, Philadelphia College of Osteopathic Medicine, 4170 City Ave, Philadelphia, PA 19131, USA