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: This case emphasizes the need for increased awareness of hemolytic reactions to all cephalosporins .
### Output Text:
This case emphasizes the need for increased awareness of hemolytic reactions to all <span class="chemical">cephalosporins</span> . 