Polymyxin Susceptibility Testing Remains Technically Challenging Despite Growing Clinical Need
As polymyxins become last-resort antibiotics for multidrug-resistant Gram-negative infections, accurate susceptibility testing is critical yet fraught with difficulties. This review details how the multicomponent drug composition, poor agar diffusion, plate adsorption, heteroresistance, and the emergence of plasmid-mediated mcr resistance genes all compromise current testing methods and complicate clinical decision-making.
The original study
Antimicrobial Susceptibility Testing for Polymyxins: Challenges, Issues, and Recommendations.
- Authors
- Ezadi F, Ardebili A, Mirnejad R
- Journal
- Journal of clinical microbiology
- Type
- Journal Article, Research Support, Non-U.S. Gov't, Review
- PMID
- 30541939
Original abstract
Polymyxins, including polymyxin B and polymyxin E (colistin), are now increasingly being used worldwide to treat patients with multidrug-resistant (MDR) Gram-negative bacterial infections. This necessitates that laboratories employ an accurate and reliable method for the routine performance of polymyxin susceptibility testing. A number of reasons have accounted for the difficulties with susceptibility testing for the polymyxins, including their multicomponent composition, poor diffusion in the agar medium, adsorption to microtiter plates, the lack of a reliable susceptibility test, the lack of a specific breakpoint from professional organizations, the synergistic effect of polysorbate 80, and the development of heteroresistance. This minireview discusses such problems that impact the results of currently available susceptibility testing methods. We also provide emerging concepts on mechanisms of polymyxin resistance, including chromosomally and plasmid-mediated mcr-related resistance. Broad-range investigations on such critical issues in relation to polymyxins can be beneficial for the implementation of effective treatment against MDR Gram-negative bacterial infections.