Case Reports

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

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Background: Aerococcus urinae (A urinae), considered a rare pathogen, has been identified with increasing frequency in urine cultures. Only 8 cases of spondylodiscitis due to A urinae have been reported. 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.

Case Presentation: A 74-year-old man presented to the emergency department after 2 weeks of midthoracic back pain, lower extremity weakness, gait imbalance, fatigue, anorexia, rigors, and subjective fevers. The patient was presumed to have discitis secondary to a urinary tract infection with possible pyelonephritis and was given empiric vancomycin and ceftriaxone. Spinal magnetic resonance imaging with contrast supported spondylodiscitis. Preliminary results from the admission blood and urine cultures showed gram-positive cocci in clusters.

Conclusions: A urinae urinary tract infection in the absence of obvious predisposing factors should prompt evaluation for urinary outflow obstruction. We suspect a review of a US Department of Veterans Affairs population might uncover a higher incidence of A urinae infection than previously suspected.


 

References

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.4-6 A 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);

whereas the final blood culture result was A urinae in all 4 bottles (2 aerobic, 2 anaerobic). Whereas the blood isolate was susceptible to all 6 tested agents, the A urinae urine isolate was susceptible to meropenem and vancomycin but intermediate to penicillin and ceftriaxone and resistant to levofloxacin (Table 2).
Transthoracic echocardiography, which was limited by body habitus, showed no vegetations or other valvular abnormalities. The patient declined transesophageal echocardiography. Repeat blood cultures from day 3 were negative.

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