AMPs are promising antimicrobials against multi-resistant bacteria. Here I study the effect of the AMP nisin combined with the chelator EDTA on three strains of the gramnegative bacteria E. coli with varying resistance. A systematic study of the development of resistance against the substances was also carried out. Results indicate a limited ability to evolve resistance against nisin and EDTA. There are however signs of cross resistance with some other AMPs and the disinfectant BAC. Moreover I found that the mechanisms of resistance resembled each other and that most were based on the layer of LPS found on gram-negative bacteria. These findings could serve as a basis for future research.