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: OBJECTIVE : To report a case of multiple episodes of seizure activity in an AIDS patent following amphotericin B infusion .
### Output Text:
OBJECTIVE : To report a case of multiple episodes of seizure activity in an AIDS patent following <span class="chemical">amphotericin B</span> infusion . 