An Elderly Patient With Lumbar Spondylodiscitis and Psoas Abscess: Diagnostic Considerations in the Context of Aerococcus urinae

<i>Aerococcus urinae</i> is an emerging Gram-positive uropathogen increasingly detected in elderly patients with structural abnormalities of the urinary tract. Although often dismissed as a contaminant, recent evidence highlights its potential to cause invasive infections, including infective endocarditis and, in rare cases, vertebral osteomyelitis or spondylodiscitis. Few such spinal infections have been reported to date. We describe the case of an 83-year-old man with a history of resected penile carcinoma (pT1a, R0; partial penectomy and bilateral inguinal lymphadenectomy in 2016), and chronic bladder outlet obstruction with associated diverticula, who presented with leukocytosis, elevated inflammatory markers, hypotension, and progressive functional decline. Initial contrast-enhanced CT imaging revealed lumbar spondylodiscitis at the L2/L3 level, with an associated left-sided psoas abscess. MRI of the lumbar spine subsequently confirmed the diagnosis and showed no evidence of intraspinal extension. While repeated blood cultures remained negative, two sequential urine cultures yielded high-count <i>A. urinae</i>; <i>Enterococcus faecalis</i> was additionally isolated from the second urine sample. In light of the patient's advanced age, moderate frailty, and clear clinical improvement under antimicrobial therapy, surgical intervention was not pursued. He was managed without surgical intervention, receiving intravenous piperacillin/tazobactam followed by oral ciprofloxacin, which resulted in clinical stabilization and declining inflammatory markers. At the first follow-up visit, 10 days after hospital discharge, CRP had decreased substantially (3.9 mg/dL), and the patient's general condition had improved. At a second follow-up appointment, seven weeks after discharge, CRP had further declined to 1.5 mg/dL, leukocyte count had normalized (6.3 × 10⁹/L), and the patient reported significant pain relief. Antimicrobial therapy was completed as planned, and a further clinical evaluation is scheduled in three weeks at the trauma surgery outpatient clinic. This case highlights the diagnostic challenges of spinal infections in elderly patients, especially when urine cultures yield multiple potential pathogens. While blood cultures are typically considered more indicative of hematogenous spinal infections, the repeated high-count isolation of <i>A. urinae</i> from urine - combined with consistent clinical and radiological findings, and the exclusion of other sources - supports its role as the presumptive pathogen in this case. Increased clinical awareness of <i>A. urinae</i> as a potentially invasive organism - even in the absence of bacteremia - is warranted, particularly in severely frail elderly patients for whom invasive diagnostics or surgical interventions may not be feasible.