There is no confusion about MIC value, it is minimum inhibitory concentration that inhibit bacterial growth. It may be reversible or irreversible both. Yes, it is possible that it might inhibit ABC channels, cationic and anionic pumps or any other pump located on membrane surface which is responsible for ion trafficking. But it may be quite different than MIC. EPIs shows active binding to the surface molecule having some charge, but MIC can include the diffusion based action through bacterial cell wall.