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: Acute renal failure in patients with AIDS on tenofovir while receiving prolonged vancomycin course for osteomyelitis .
### Output Text:
Acute renal failure in patients with AIDS on <span class="chemical">tenofovir</span> while receiving prolonged <span class="chemical">vancomycin</span> course for osteomyelitis . 