Editor's choice: Implications of isoniazid resistance in Mycobacterium bovis Bacillus Calmette-Guérin used for immunotherapy in bladder cancer.

We report a case of sepsis from Mycobacterium bovis Bacillus Calmette-Guérin (BCG) with low-level isoniazid resistance following intravesical treatment for bladder cancer. Isoniazid resistance in BCG has therapeutic implications when it causes infections after intravesical instillation. For these circumstances, we propose some modifications to existing treatment guidelines for BCG infection.