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 present a patient with fatal acetaminophen - induced fulminant hepatic failure , with signs and symptoms of cerebral edema , unresponsive to conventional medical therapy .
### Output Text:
We present a patient with fatal <span class="chemical">acetaminophen</span> - induced fulminant hepatic failure , with signs and symptoms of cerebral edema , unresponsive to conventional medical therapy . 