In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: We report a case of reversible olfactory disorder related to pyrazinamide in a woman , with a positive rechallenge .
### Output Text:
We report a case of reversible olfactory disorder related to <span class="chemical">pyrazinamide</span> in a woman , with a positive rechallenge . 