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: A case of oral penicillin anaphylaxis is described , and the terminology , occurrence , clinical manifestations , pathogenesis , prevention , and treatment of anaphylaxis are reviewed .
### Output Text:
A case of oral <span class="chemical">penicillin</span> anaphylaxis is described , and the terminology , occurrence , clinical manifestations , pathogenesis , prevention , and treatment of anaphylaxis are reviewed . 