A Case Report of Aerococcus urinae Urinary Tract Infection in an Elderly Male with Multimorbidity

Abstract

Aerococcus urinae is a rare cause of urinary tract infection (UTI) seen in elderly males with multimorbidity. Incidence is estimated between 0.15 and 0.8%. This organism is frequently misidentified for other grampositive species. Missed or delayed diagnosis of A. urinae UTI can lead to systemic infection with high morbidity and potential mortality. We present a classic case of A. urinae UTI in a 91-year-old male with multiple comorbidities, including heart failure, diabetes mellitus, and metastatic prostate carcinoma. Empiric therapy with nitrofurantoin was unsuccessful, but intravenous ceftriaxone and bladder catheterization resulted in rapid symptomatic improvement. Variable antimicrobial sensitivities and resistance have been reported for A. urinae. Therefore, antimicrobial resistance testing should be performed for all patients with A. urinae infections.

Aerococcus urinaeurinary tract infection in a hospitalised patient: an increasingly common infection

“…Despite this case of an A. urinae urinary tract infection being relatively uncomplicated, the confirmed case helps illustrate this organism’s slowly increasing incidence as a cause of urinary tract infections. Most cases published in the last ten years identify A. urinae as a rare and avirulent organism; however, our knowledge of its pathogenicity and incidence is changing as more cases are diagnosed and treated 3 7 8. The growing incidence could be due to several reasons, two of which will be discussed below.…”

“…The growing incidence could be due to several reasons, two of which will be discussed below. First, A. urinae appears to have a predilection for a specific population of patients, which may also be related to its virulent qualities 1 3. Second, advancement in the ability to isolate A. urinae has decreased the misclassification rate and may be unmasking its true incidence 1 3 9–11…”

“…It is well documented that A. urinae almost exclusively causes urinary tract infections in male patients 65 years or older, with comorbid conditions such as coronary artery disease, previous stroke, diabetes mellitus, chronic kidney disease, chronic obstructive pulmonary disease, various malignancies and urological diseases like benign prostatic hyperplasia 1 3 10 . A. urinae has been described as having low pathogenicity since its discovery in 1992 2.…”

“…A. urinae also has unique antibiotic considerations when treated as a urinary tract infection, as it is commonly noted to be resistant to fluoroquinolones and sulfamethoxazole, making these agents less effective as empiric therapies 14. As such, early detection and sensitivity testing are essential in managing A. urinae urinary tract infection 3. As the suspected incidence of A. urinae continues to rise, it is essential to recognise it as a virulent pathogen in urinary tract infections when ordering diagnostic studies and initiating empiric antibiotic therapy, especially if a patient fits the archetype of our patient described above.…”

“…Since its discovery in 1992, cases of A. urinae infections have been described as a ‘rare’ occurrence, with one hospital study describing the incidence of A. urinae bacteraemia as 3 per 1 million inhabitants per year, and another study describing the incidence of A. urinae urinary tract infections as 54 per 1 million inhabitants per year 1 2. Currently, the overall incidence of A. urinae urinary tract infections remains somewhat low, between a suspected 0.15% and 0.8% 3. However, it has been questioned whether the incidence of A. urinae urinary tract infections may be higher than expected due to its frequent misclassification during culturing and inherent pathogenicity towards a specific patient population 1.…”