Efficacy of six frog skin-derived antimicrobial peptides against colistin-resistant strains of the Acinetobacter baumannii group

Abstract 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)≤2μg/mL] and colistin-resistant (MIC≥64μg/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=4–16μg/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.