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: Light chain proteinuria was found in 9 of 17 tuberculosis patients treated with rifampin .
### Output Text:
Light chain proteinuria was found in 9 of 17 tuberculosis patients treated with <span class="chemical">rifampin</span> . 