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: Haematological adverse reactions associated with fatal outcome are rare during treatment with ciprofloxacin .
### Output Text:
Haematological adverse reactions associated with fatal outcome are rare during treatment with <span class="chemical">ciprofloxacin</span> . 