Gene-Gene Interactions Reduce Aminoglycoside Susceptibility of through Efflux Pump-Dependent and -Independent Mechanisms.

causes a wide range of acute and chronic infections. Aminoglycosides are a cornerstone of treatment, but isolates are often resistant. The purpose of this research was to better understand the genetic basis of aminoglycoside resistance in . Bioinformatic approaches identified mutations in resistance-associated genes in the clinical isolates of . The common mutations were then engineered into the genome of reference strain PAO1. Mutations in the elongation factor gene caused the biggest reduction in aminoglycoside susceptibility, with mutations in the two-component regulator gene and the efflux pump regulator gene having less impact. This susceptibility was further reduced by combinations of mutations. Mutations in , and all increased the expression of the efflux pump that is strongly associated with aminoglycoside resistance. Furthermore, the triple mutant had the highest efflux pump gene expression. Engineering and mutants lacking this efflux pump showed that and also reduce aminoglycoside susceptibility through additional mechanisms. The and mutations reduced bacterial growth, showing that these mutations have a fitness cost. Our findings demonstrate the complex interplay between mutations, efflux pump expression and other mechanisms for reducing the susceptibility of to aminoglycosides.