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: Amikacin is an aminoglycoside commonly used to provide empirical double gram - negative treatment for febrile neutropenia and other suspected infections .
### Output Text:
<span class="chemical">Amikacin</span> is an <span class="chemical">aminoglycoside</span> commonly used to provide empirical double gram - negative treatment for febrile neutropenia and other suspected infections . 