The invention relates to isolated and purified antimicrobial peptides from tilapia (Oreochromis niloticus) gill extracts. Said peptides can be produced by chemical synthesis or in heterologous expression systems, such as bacteria and yeast, by conventional molecular biology techniques. Said peptides exhibit antimicrobial activity against various organisms including gram-positive bacteria, gram-negative bacteria, fungi and viruses. The invention also includes compositions for controlling pathogenic agents, comprising said antimicrobial peptides. The invention further relates to the use of said peptides as a molecular adjuvant in vaccine preparations.
