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: Intravenous inoculation of 4 . 2 x 10 ( 10 ) to 7 . 8 x 10 ( 10 ) pyocin type 6 Pseudomonas organisms in monkeys given vincristine sulfate 4 days previously resulted in fatal infection in 11 of 14 monkeys , whereas none of four receiving Pseudomonas alone died .
### Output Text:
Intravenous inoculation of 4 . 2 x 10 ( 10 ) to 7 . 8 x 10 ( 10 ) pyocin type 6 Pseudomonas organisms in monkeys given <span class="chemical">vincristine sulfate</span> 4 days previously resulted in fatal infection in 11 of 14 monkeys , whereas none of four receiving Pseudomonas alone died . 