Chryseobacterium species are environmental Gram-negative bacilli that rarely cause human infections. While Chryseobacterium-related infections have been reported in immunocompromised patients, cases involving prostatitis are exceedingly rare.

A 95-year-old Japanese man with a history of hypertension and dementia underwent urinary catheter placement one month earlier due to urinary retention caused by benign prostatic hypertrophy (BPH), with a prostate volume of 156 mL. He was referred to our hospital for surgical management of BPH. Preoperative urinalysis revealed pyuria, with a white blood cell count of 50–99 per high-power field, and bacteriuria. To prevent perioperative infection, intravenous tazobactam/piperacillin (TAZ/PIPC) at a dose of 4.5 g twice daily was administered for two days prior to transurethral water vapor energy therapy (WAVE). Following surgery, the patient developed a fever exceeding 38°C. Physical examination demonstrated prostate tenderness on digital rectal examination. No signs of respiratory infection, abdominal pathology, pyelonephritis, or epididymitis were noted. Contrast-enhanced chest-to-pelvis CT revealed enhancement of the prostate and haziness of the periprostatic fat tissue. No other findings suggestive of the source of fever were identified in the remaining organs. Based on clinical findings, a diagnosis of acute prostatitis was made. Initial laboratory tests showed leukocytosis (10,180/μL), neutrophilia (77.8%), and elevated C-reactive protein (CRP) level (6.2 mg/dL). Antimicrobial therapy with TAZ/PIPC was continued.

The patient continued to have a fever despite five days of TAZ/PIPC therapy. At that time, the results of the preoperative urine culture became available and a Chryseobacterium species was the only organism identified. This organism was resistant to many antibiotics, including TAZ/PIPC, but was susceptible to minocycline; therefore, intravenous administration of minocycline was initiated. After five days of intravenous therapy, the patient showed a trend toward resolution of fever. Subsequently, oral minocycline was continued for an additional five days. Following completion of the antibiotic course, the patient’s leukocyte count and CRP level improved. He was discharged on postoperative day 28. Three months after surgery, the patient was able to void spontaneously, and the urinary catheter was successfully removed. Follow-up urine culture performed five months postoperatively showed no evidence of Chryseobacterium colonization.

This case highlights the importance of considering Chryseobacterium as a rare but potential pathogen in cases of prostatitis, especially in patients with specific risk factors including catheterization. Early identification and appropriate antibiotic management are crucial for favorable outcomes.