Polymyxin B and ethylenediaminetetraacetic acid act synergistically against Pseudomonas aeruginosa and Staphylococcus aureus .

Bacteria living in biofilms produce a protective matrix which makes them difficult to kill. Patients with severe respiratory disease often have biofilms. Polymyxin B is an antibiotic commonly used in topical medications, such as eye drops and nasal sprays. Ethylenediaminetetraacetic acid (EDTA) is used widely as a preservative in medication but also has antimicrobial properties. It has been hypothesized that Polymyxin B and EDTA could have a synergistic relationship: when used in combination their antimicrobial effect is enhanced. Here, we evaluated the levels at which Polymyxin B and EDTA work together to kill common pathogens Pseudomonas aeruginosa and Staphylococcus aureus . We found that Polymyxin B and EDTA were synergistic. This synergy may be useful in the management of planktonic infection with P. aeruginosa and S. aureus , or biofilm infection with P. aeruginosa . This synergy may be beneficial in the treatment of respiratory biofilms, in which P. aeruginosa biofilms are common.