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: However , macrolide antimicrobials have been reported to be associated with hiccups and vagal mechanism could explain the development of this side - effect .
### Output Text:
However , <span class="chemical">macrolide</span> antimicrobials have been reported to be associated with hiccups and vagal mechanism could explain the development of this side - effect . 