In vitro activity of prodigiosin isolated from serratia marcescens in combination with two groups of antibiotics against gram-negative microorganisms

Abstract

Frequent and unrestricted use of antibiotics has been associated with the development of antibiotic resistance by microorganisms. Thus, there is a need to find novel antibacterial agents or a combination of agents as the first line of treatment for various infections. Combination therapy is generally an effective strategy to fight resistance, while some data on its effects are conflicting. To explore the reasons, the fractional inhibitory concentration indexes (FICIs) of two designed combinations against the genera Escherichia, Pseudomonas, and Proteus determined using the microdilution method, and their minimal concentrations inhibiting colony formation by 99% (MIC 99%) alone or in combinations including different proportions.