Hyperammonemia and Impaired Consciousness Caused by Non-Urease-Producing Actinotignum schaalii in Obstructive Urinary Tract Infection

Urinary tract infections (UTIs) caused by urease-producing bacteria are known to cause hyperammonemia; however, non-urease-producing bacteria can also cause it. This report describes a case of an 87-year-old woman who developed hyperammonemia and impaired consciousness resulting from a UTI caused by the non-urease-producing bacterium, <i>Actinotignum schaalii</i> (<i>A. schaalii</i>). On admission, the patient presented with urinary retention, hyperammonemia (281 μg/dL), and alkaline urine (pH 8.5). Gram staining of urine revealed the presence of gram-positive bacilli with coryneform morphology, which was suggestive of <i>A. schaalii</i> or <i>Corynebacterium</i>, with some being urease-producing bacteria. After bladder decompression through catheterization, the patient's level of consciousness improved within 30 minutes, and the ammonia level normalized. The patient's condition stabilized after ceftriaxone treatment, and she was discharged after nine days. This case demonstrated that non-producing bacteria can cause hyperammonemia and may acquire urease activity within an infected environment. In cases of hyperammonemia associated with obstructive urinary tract disorders, it is necessary to consider both urease-producing and non-urease-producing bacteria. Further, upon identification of a gram-positive bacillus, it is important to select an appropriate antimicrobial agent.