Case Presentation: A 69-year-old man with a past medical history of symptomatic sick sinus syndrome with a permanent pacemaker (PPM), as well as benign prostatic hyperplasia (BPH), initially presented to the hospital with substernal chest pain after lifting boxes.
A complete cardiac evaluation, including ischemic work-up and transthoracic echocardiography, was conducted without evidence of active cardiac disease; plans were made for outpatient followup.
During his hospitalization, the patient reported dysuria and groin pain, and endorsed a previously unreported history of recurrent urinary tract infections (UTIs). He subsequently became febrile and underwent a full sepsis work up. Preliminary urinalysis showed leukocyte esterase, white blood cells, and many bacteria, with the culture growing mixed flora. Blood cultures revealed gram positive cocci in clusters (2/4 bottles), which ultimately speciated after additional testing as Aerococcus urinae. CT of the abdomen and pelvis revealed small non-obstructing stone and no signs of pyelonephritis.
Given concerns for his indwelling hardware in the setting of bacteremia, a transesophageal echocardiogram was obtained, which revealed a large tricuspid valve vegetation sparing the PPM wire. The patient’s course was then complicated by progressive back and hip pains and rapidly increasing inflammatory markers. A repeat CT abdomen, pelvis, and lumbar spine showed new L3/L4 lucencies consistent with osteomyelitis, thought likely due to Aerococcus (biopsy deferred).
The patient ultimately underwent PPM extraction, temporary epicardial pacing, and device replacement, as well as extended course of IV cefepime for his systemic infection.
Discussion: Aerococcus urinae is an uncommon organism that grows in gram-positive clusters, and which is both alpha hemolytic and catalase negative. It is associated with UTIs in elderly men (median age 79 years) and is often seen in the setting of indwelling catheters and structural abnormalities such as BPH, urethral strictures, and nephrolithiasis. Dipstick analysis are usually negative for nitrites but may be positive for leukocyte esterase and protein; urine cultures are often negative, due to special medium requirements that are not consistently performed in laboratories. Ampicillin-based regimens are the treatment of choice; interestingly, A. urinae is often resistant to ciprofloxacin, which may reflect resistance patterns in patients treated for recurrent UTIs.
Conclusions: Aerococcus urinae is a rare microorganism usually found in the urinary tract, which until recently was thought to be a urinary contaminant lacking clinical significance. It is now being recognized as an emerging cause of UTIs, especially in elderly males with urologic conditions, with the potential to cause bacteremia if not appropriately treated. Few cases of Aerococcus-associated endocarditis or other disseminated infections have been reported, and prognosis among these patients is often reported to be poor. Due to advancement in detection and identification methods, diagnosis and treatment of this emerging pathogen continues to improve.