Polymyxin b sulfate and trimethoprim ophthalmic solution usp is used for

Bacterial infections (such as blepharitis, conjunctivitis)

Explanation:

  Antibiotics are substances that have the ability to inhibit growth and / or destroy  microorganisms. They may be produced by bacteria or fungi or may be total or  partially synthetic.  The main purpose of using an antimicrobial is to prevent or treat an infection, reducing or eliminating pathogenic organisms.

   Polymyxin B and ophthalmic trimethoprim is a combination medicine used to treat eye infections caused by bacterias.  

 Polymyxin b sulfate: has a bactericidal antimicrobial action and acts primarily on outer membranes  and cytoplasmic.