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: Thrombophlebitis occurred only with infusion through peripheral cannulae ; nephrotoxicity and ototoxicity were confined to patients receiving an aminoglycoside plus vancomycin .
### Output Text:
Thrombophlebitis occurred only with infusion through peripheral cannulae ; nephrotoxicity and ototoxicity were confined to patients receiving an <span class="chemical">aminoglycoside</span> plus <span class="chemical">vancomycin</span> . 