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: CONCLUSIONS : Reversible inferior colliculus lesions could be considered as the characteristic for metronidazole - induced encephalopathy , next to the dentate nucleus involvement .
### Output Text:
CONCLUSIONS : Reversible inferior colliculus lesions could be considered as the characteristic for <span class="chemical">metronidazole</span> - induced encephalopathy , next to the dentate nucleus involvement . 