Comparative activities of polycationic peptides and clinically used antimicrobial agents against multidrug-resistant nosocomial isolates of Acinetobacter baumannii.

The in vitro activity of buforin II, cecropin P1, indolicidin, magainin II and ranalexin, alone and in combination with eight clinically used antimicrobial agents was investigated against 12 multidrug-resistant strains of Acinetobacter baumannii isolated from immunocompromised patients. Antimicrobial activities were measured by MIC, MBC and viable count. The peptides had a varied range of inhibitory values: overall, the organisms were more susceptible to buforin II (MIC range 0.25-16 mg/L), cecropin P1 (0.50-32 mg/L) and magainin II (0.50-16 mg/L). Synergy occurred when magainin II was combined with beta-lactam antibiotics.