CP 4 - Oligella ureolytica urosepsis in an elderly woman: A rare case report

Shanthakumara WDDI, Marikkar FTN, Edirisooriya Arachchi PS, Rathnayaka S, Sulaimalebbe AS  , Department of Microbiology, Colombo South Teaching Hospital

Abstract

Introduction

Oligella ureolytica is a rare aerobic Gram-negative coccobacillus and an uncommon cause of human infection. Along with Oligella urethralis, it is one of the two recognized pathogenic species within the genus Oligella. Reported infections usually occur in elderly patients with urinary tract abnormalities or long-term catheterization. We report a case of O. ureolytica urosepsis in an elderly woman without these risk factors.

Case Report

An 86-year-old woman with bronchial asthma and ischaemic heart disease presented with fever and urinary symptoms, accompanied by elevated white blood cell count and C-reactive protein levels. A clinical diagnosis of urosepsis was made, and empirical treatment with intravenous ceftriaxone was initiated, resulting in prompt resolution of the fever.

Urinalysis revealed a field full of pus cells; however, urine culture yielded no growth. Blood cultures became positive, and Gram looked like Gram-negative diplococci, initially raising suspicion of Neisseria meningitidis. However, the clinical presentation suggested a urinary source of infection, prompting further microbiological investigation.

Culture yielded small, circular, convex, non-haemolytic colonies on blood and chocolate agar. The isolate was oxidase-positive, catalase-positive, and non-motile. Growth as a non-lactose fermenter on MacConkey agar excluded Neisseria species. The oxidase-positive, non-lactose-fermenting phenotype initially suggested Pseudomonas species; however, susceptibility to co-amoxiclav, cefotaxime, and penicillin was atypical. VITEK 2 identified the organism as Oligella ureolytica with 93% probability. This identification was supported by a strongly positive urease test. The patient recovered uneventfully with ceftriaxone therapy.

Discussion

O.ureolytica is an uncommon pathogen that may be overlooked or misidentified in routine microbiology laboratories. Reported infections include urinary tract infections, bacteraemia, urosepsis, septic arthritis, and peritonitis. Most cases occur in patients with advanced age, urinary tract abnormalities, urinary obstruction, malignancy, immunosuppression, or prolonged catheterization. Notably, our patient lacked these recognized risk factors.

Identification can be challenging, as the organism may be misidentified as Pseudomonas spp. in routine culture if further testing is not performed. Urease positivity was useful in differentiating O. ureolytica from urease-negative Pseudomonas species. This case highlights the pathogenic potential of O. ureolytica and the need for accurate laboratory identification of rare urinary pathogens causing invasive infection.