Cecropin

Ceragenins (CSA-13, CSA-44, CSA-90, CSA-131, CSA-131-poloxamer (CSA-131P), CSA-138, CSA-142, CSA-144 and CSA-192) were synthesized from cholic acid. AMPs (magainin, cecropin, and LL-37) and Pluronic® F127 used to prepare CSA-131-poloxamer were obtained from Sigma-Aldrich (St. Louis, MO, USA). Stock solutions of ceragenins and AMPs were prepared by dissolving the materials in distilled water and storing at −20 °C for a maximum of one month. CSA-131 was combined with 5% Pluronic F-127 to form CSA-131-poloxamer and stored at room temperature. P. aeruginosa-GFP (ATCC^® 10145GFP™) containing a multicopy vector encoding the green fluorescent was used in the study.

Overnight grown culture of wild-type and mutant strains was subcultured for 4 h. Cells were washed with PBS and diluted to approximately 10⁸ CFU/ml. A 50 µl aliquot of bacterial suspension was incubated at 37 °C for 1 h with or without AMPs, polymyxin B; 1 µg/ml (Sigma), protamine; 5 µg/ml (Himedia, India), LL37; 10 µg/ml (Sigma), cecropin; 2 µg/ml (Sigma) in PBS. Subsequently, samples were serially diluted and plated on LB agar plates to obtain the number of surviving bacteria. The survival efficiency was calculated as percent ratio of the CFU obtained from AMP treated culture versus untreated culture. Experiment was repeated thrice in triplicates.