Epistasis

Epistasis is a phenomenon in genetics in which the interaction between genes influences a phenotype.

Epistasis describes the effect of combining mutations that have an effect on the same phenotype. Several resistance mutations can accumulate under antibiotic treatment and epistatic effects affect fitness in bacteria and the resistance phenotype.

Epistasis: Gene Interaction and Phenotype Effects (Nature Education, 2008)

Epistasis between antibiotic resistance mutations and genetic background shape the fitness effect of resistance across species of Pseudomonas (Proceedings of the Royal Society B, 2016) 

Global Epistasis Emerges from a Generic Model of a Complex Trait (eLife, 2021)

Highly parallel lab evolution reveals that epistasis can curb the evolution of antibiotic resistance (Nature Communications, 2020)