The emergence of Acinetobacter sp. strains resistant to all antibacterial agents including colistin necessitates the development of new types of antimicrobial agents. Six cationic α-helical frog skin-derived peptides (CPF-AM1, PGLa-AM1, B2RP-ERa, [E4K]alyteserin-1c, [D4K]B2RP and [G4K]XT-7) were selected for this study on the basis of potent growth-inhibitory activity against Gram-negative bacteria and low haemolytic activity against human erythrocytes. All peptides were active against a range of colistin-susceptible [minimum inhibitory concentration (MIC)≤2 μg/mL] and colistin-resistant (MIC≥64 μg/mL) clinical isolates of multidrug-resistant strains of Acinetobacter baumannii and Acinetobacter nosocomialis. The most potent peptides against the colistin-resistant strains were [D4K]B2RP and [E4K]alyteserin-1c (MIC=4-16 μg/mL for both). The MIC values of these peptides against the colistin-susceptible strains were in the same range. The frog peptides show potential for development into drugs to treat infections caused by pandrug-resistant Gram-negative pathogens.
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