Cystitis Caused by Citrobacter amalonaticus in an Older Outpatient in the Absence of Catheterization

Citrobacter amalonaticus (C. amalonaticus) is a rarely isolated member of the Citrobacter genus and an uncommon cause of human infection. Although Citrobacter species are recognized uropathogens, the clinical significance of C. amalonaticus in urinary tract infections (UTIs) remains poorly characterized. We report a case of cystitis caused by C. amalonaticus in an 87-year-old woman who visited our outpatient clinic owing to urinary symptoms. She had previously received medication for an overactive bladder and had persistent postvoid residual urine. Urine culturing yielded only C. amalonaticus, and the patient was successfully treated with levofloxacin. Reports of cystitis caused by C. amalonaticus in non-catheterized outpatients are extremely limited. In older patients, urinary tract infections are often associated with comorbidities and impaired bladder emptying, which may predispose them to infections by uncommon organisms. This case highlights the fact that C. amalonaticus can act as a uropathogen in older patients with urinary stasis, even in the absence of catheterization. Clinicians should be aware that this rare organism is a potential cause of urinary tract infections.