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: Skin tests were performed with benzylpenicilloyl - poly - L - lysine ( BPO - PLL ) , benzylpenicilloate , benzylpenicillin ( PG ) , ampicillin ( AMP ) , and AX .
### Output Text:
Skin tests were performed with <span class="chemical">benzylpenicilloyl - poly - L - lysine</span> ( <span class="chemical">BPO - PLL</span> ) , <span class="chemical">benzylpenicilloate</span> , <span class="chemical">benzylpenicillin</span> ( <span class="chemical">PG</span> ) , <span class="chemical">ampicillin</span> ( <span class="chemical">AMP</span> ) , and <span class="chemical">AX</span> . 