Oral Therapy for Aerococcus urinae Bacteremia and Thoracic Spondylodiscitis of Presumed Urinary Origin

Aerococcus urinae (A urinae), a gram-positive coccus readily mistaken for a Staphylococcus species, was first identified in 1992.^1-3 It now reportedly accounts for 0.2% to 0.8% of clinical urine isolates.^4-6A urinae bacteriuria is typically asymptomatic and mainly occurs in women.^7-9 Symptomatic A urinae urinary tract infection (UTI) occurs predominantly in older men with underlying urologic abnormalities.^4-10 

Serious A urinae infections are rare. The first 2 reported cases involved men with A urinae endocarditis, one of whom died.^11,12 To date, only 8 cases of spondylodiscitis due to A urinae have been reported.^13-20 Optimal treatment for invasive A urinae infection is undefined; however, the reported cases were treated successfully with diverse antibiotic regimen combinations; all including a β-lactam and beginning with at least 2 weeks of IV antibiotics.^13-20 We describe a man with A urinae bacteremia and spondylodiscitis, presumably arising from a urinary source in the setting of bladder outlet obstruction, who was treated successfully.

Case Presentation

A 74-year-old man with morbid obesity, type 2 diabetes mellitus, stage 2 chronic kidney disease, and tobacco use presented to the emergency department after 2 weeks of progressive, nonradiating, midthoracic back pain, lower extremity weakness, gait imbalance, fatigue, anorexia, rigors, and subjective fevers. On presentation, he was afebrile and hemodynamically stable. A physical examination revealed point tenderness of the midthoracic vertebrae, nontender costovertebral angles, diffusely decreased strength, nonsustained clonus in both lower extremities, inguinal intertrigo, and a buried penis with purulent meatal discharge.

Laboratory results indicated a white blood cell (WBC) count of 13.5 K/μL (reference range, 4.0-11.0), absolute neutrophil count of 11.48 K/μL (reference range, 2.0-7.7), C-reactive protein (CRP) level of 225.3 mg/L (reference range, ≤ 5.0), erythrocyte sedimentation rate of 85 mm/h (reference range, 5-15), serum blood urea nitrogen of 76 mg/dL (reference range, 8-26), and serum creatinine (SCr) of 1.9 mg/dL (reference range, 1.1-1.4). A urinalysis showed positive leukocyte esterase, WBC clumps, and little bacteria. Abdominal/pelvic computed tomography showed spondylodiscitis-like changes at T7-T8, bilateral perinephric fat stranding, bladder distension, and bladder wall thickening.

The patient was presumed to have discitis secondary to a UTI, with possible pyelonephritis, and was given empiric vancomycin and ceftriaxone. Spinal magnetic resonance imaging with contrast supported spondylodiscitis at T7-T8, extending to T8-T9. Preliminary results from the admission blood and urine cultures showed gram-positive cocci in clusters, which were presumed initially to be Staphylococcus aureus (S aureus).

The final urine culture report listed multiple organisms, predominantly A urinae (Table 1);