A high throughput method for screening cDNA libraries has been developed to identify putativeantimicrobial peptides (AMPs). It is based on a rapid dye inclusion assay for assessing antagonism ofbacterial viability. Colonies are grown on a membrane on a permissive medium until full colony size isreached. The membrane, supporting the array of colonies, is transferred onto an inductive mediumcontaining a vital dye. Upon expression of any antagonizing peptides, the cell membrane becomescompromised allowing dye infusion to permit visual identification of deleterious peptides.Our approach was validated by screening a synthetic oligonucleotide library expressed in Escherichia coli. Arandom oligonucleotide library, containing inserts of up to 75 nucleotides in length was constructed andexpressed in E. coli. From a potential pool of 100 000 peptides, in a single round of screening, three werefound to be antimicrobial: L1, L3, and L8. Peptide L1 was shown to have a concentration-dependentbactericidal effect against Gram-negative E. coli and moderate biostatic activity against the Gram-positivebacteria Listeria monocytogenes. L8 was found to have bacteriostatic, and possibly bactericidal effect againstE. coli, Pseudomonas aeruginosa and Salmonella typhimurium. These results validated this high throughputAMP identification assay based on filter bound colony array libraries and vital dye inclusion.