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: Dehydrated rats regularly develop acute renal failure following single injection of aminoglycoside antibiotics combined with dextran or of antibiotics only .
### Output Text:
Dehydrated rats regularly develop acute renal failure following single injection of <span class="chemical">aminoglycoside</span> antibiotics combined with dextran or of antibiotics only . 