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: Changing epidemiology of infections such as infective endocarditis ( IE ) has led to an increase in the use of rifampicin for Staphylococcal infections .
### Output Text:
Changing epidemiology of infections such as infective endocarditis ( IE ) has led to an increase in the use of <span class="chemical">rifampicin</span> for Staphylococcal infections . 