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: We prospectively compared the efficacy and safety of netilmicin sulfate or tobramycin sulfate in conjunction with piperacillin sodium in 118 immunocompromised patients with presumed severe infections .
### Output Text:
We prospectively compared the efficacy and safety of <span class="chemical">netilmicin sulfate</span> or <span class="chemical">tobramycin sulfate</span> in conjunction with <span class="chemical">piperacillin sodium</span> in 118 immunocompromised patients with presumed severe infections . 