Final answer:
Polymixin B should work on Escherichia Coli because it is a Gram-negative antibiotic that disrupts the bacterium's outer membrane, making the statement true.
Step-by-step explanation:
The statement that Polymixin B should have worked on Escherichia Coli because it is Gram-negative is true. Polymixin B is an antibiotic that targets the outer membrane of Gram-negative bacteria, disrupting their structure and leading to cell death. Since E. coli is Gram-negative, the outer membrane is susceptible to this type of antibiotic. Polymixin B is often used as a treatment option for infections caused by Gram-negative bacteria, particularly when they are resistant to other antibiotics.