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: The aims of this study were to examine vancomycin ( VCM ) - induced oxidative stress that promotes production of reactive oxygen species ( ROS ) and to investigate the role of erdosteine , an expectorant agent , which has also antioxidant properties , on kidney tissue against the possible VCM - induced renal impairment in rats .
### Output Text:
The aims of this study were to examine <span class="chemical">vancomycin</span> ( <span class="chemical">VCM</span> ) - induced oxidative stress that promotes production of reactive <span class="chemical">oxygen</span> species ( ROS ) and to investigate the role of <span class="chemical">erdosteine</span> , an expectorant agent , which has also antioxidant properties , on kidney tissue against the possible <span class="chemical">VCM</span> - induced renal impairment in rats . 