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: This case report shows that ciprofloxacin may precipitate life - threatening thrombocytopenia and haemolytic anaemia , even in the early phases of treatment and without apparent previous exposures .
### Output Text:
This case report shows that <span class="chemical">ciprofloxacin</span> may precipitate life - threatening thrombocytopenia and haemolytic anaemia , even in the early phases of treatment and without apparent previous exposures . 