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: Although the transaminases gradually returned to baseline after withholding the beta lactam antibiotic , there was a gradual increase in serum bilirubin and a decrease in hemoglobin concentration caused by an autoimmune hemolytic anemia and erythroblastocytopenia .
### Output Text:
Although the transaminases gradually returned to baseline after withholding the <span class="chemical">beta lactam</span> antibiotic , there was a gradual increase in serum <span class="chemical">bilirubin</span> and a decrease in hemoglobin concentration caused by an autoimmune hemolytic anemia and erythroblastocytopenia . 