Oral Therapy for Aerococcus urinae Bacteremia and Thoracic Spondylodiscitis of Presumed Urinary Origin
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.
On hospital day 6, the patient’s back pain had resolved, micturition was normal, appetite had normalized, and SCr was minimally above baseline (1.4 mg/dL). He insisted on completing antibiotic treatment at home and had no other medical indication for continued hospitalization. Thus, antibiotic therapy was changed to an all-oral regimen of amoxicillin 1 g 3 times daily for 10 days and levofloxacin 750 mg daily for 6 weeks, and the patient was discharged to home.
The patient returned 5 days postdischarge due to anuria. Investigation showed severe acute kidney injury (SCr, 6.8 mg/dL) and bladder outlet obstruction due to phimosis and urethral meatal stenosis. Urinalysis was unremarkable. His CRP had declined from 225 mg/L (initial admission) to 154 mg/L. A urinae culture and 2 sets of blood cultures were finalized as no growth. He was diagnosed with postrenal acute kidney injury and underwent meatal dilation and Foley catheterization but declined surgical correction. When seen in the clinic 2 months postantimicrobial therapy, the patient had normal micturition, no symptoms or signs of infection, and steadily down-trending inflammatory markers.
Discussion
A urinae, historically considered a rare pathogen, has been identified with increasing frequency in urine cultures due to improved microbiologic diagnostic techniques. However, there are only 8 reported cases of A urinae spondylodiscitis. Urinary pathology is an accepted risk factor for A urinae infections; consequently, we suspect that our patient’s urinary outflow obstruction and poor genitourinary hygiene were related to his invasive A urinae infection.10,21,22 We surmise that he had a chronic urinary outflow obstruction contributing to his infection, as evidenced by imaging findings, while the phimosis and urethral meatal stenosis were most likely infectious sequelae considering his anuria and acute kidney injury 5 days postdischarge. Indeed, the correlation between A urinae and urinary tract pathology may justify an evaluation for urinary pathology in any man with A urinae infection, regardless of the presence of symptoms.
By contrast, the implications of A urinae bacteriuria remain unclear. From a public health perspective, A urinae bacteriuria is rare, but the infectious mechanism remains undetermined with a case report suggesting the possibility of sexual transmission.4-6,23 In our case, the patient was not sexually active and had no clear origin of infection. Considering the potential severity of infection, more studies are needed to determine the infectious mechanism of A urinae.
In terms of infectious morbidity, the results seem to vary by sex. In a retrospective study of about 30,000 clinical urine samples, 62 (58 from women, 4 from men) yielded A urinae. The 62 corresponding patients lacked systemic infectious complications, leading the authors to conclude that A urinae is a relatively avirulent organism.24 Although possibly true in women, we are wary of drawing conclusions, especially regarding men, from a study that included only 62 urine samples were A urinae–positive, with only 4 from men. More evidence is needed to define the prognostic implications of A urinae bacteriuria in men.
