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: Autoantibodies against P450 2E1 or P58 , previously associated with halothane hepatitis , were detected in the serum of five affected workers .
### Output Text:
Autoantibodies against P450 2E1 or P58 , previously associated with halothane hepatitis , were detected in the serum of five affected workers . 