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: A high percentage of kanamycin - colistin and povidone - iodine irrigations were associated with erosive cystitis and suggested a possible complication with human usage .
### Output Text:
A high percentage of <span class="chemical">kanamycin</span> - <span class="chemical">colistin</span> and <span class="chemical">povidone - iodine</span> irrigations were associated with erosive cystitis and suggested a possible complication with human usage . 