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: Of these , clarithromycin was implicated in 23 ( 27 . 6 % ) cases , ciprofloxacin in 12 ( 14 . 4 % ) cases , and ofloxacin in 10 ( 12 % ) cases .
### Output Text:
Of these , <span class="chemical">clarithromycin</span> was implicated in 23 ( 27 . 6 % ) cases , <span class="chemical">ciprofloxacin</span> in 12 ( 14 . 4 % ) cases , and <span class="chemical">ofloxacin</span> in 10 ( 12 % ) cases . 