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: Segmental necrotising glomerulonephritis has been reported as complication of rifampicin therapy in patients receiving treatment for tuberculosis .
### Output Text:
Segmental necrotising glomerulonephritis has been reported as complication of <span class="chemical">rifampicin</span> therapy in patients receiving treatment for tuberculosis . 