After each round of bacterial exposure to test peptides or standard antibiotics, the new MIC was determined as an indicator of resistance development. Interestingly, similar to the peptide-based antibiotics (daptomycin and polymyxin B), negligible changes in the MICs were observed for peptides 15c and 16c against all the tested bacterial strains. However, a continuous increase in the MICs of ciprofloxacin was observed against all the tested bacterial strains (Figures ). Overall, these results indicated that both Gram-positive and Gram-negative pathogens are unable to develop resistance against 15c and 16c.