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: In nontransgenic animals , the threshold in the kanamycin - treated group was 45 - 50 dB higher than in saline - injected controls .
### Output Text:
In nontransgenic animals , the threshold in the <span class="chemical">kanamycin</span> - treated group was 45 - 50 dB higher than in saline - injected controls . 