In view of growing number of pathogenic microbial strain resistant to routine antibiotics, antimicrobial peptides become promising agents for the therapy of infectious diseases. We studied in vivo effects of melittin, an antimicrobial peptide expressed in a recombinant plasmid vector, on infection with urogenital pathogens Chlamydia trachomatis, Mycoplasma hominis, and Mycoplasma gallisepticum. We obtained recombinant plasmid constructs, where melittin gene is under the control of tetracycline-dependent human cytomegalovirus promoter. Inhibition of experimental C. trachomatis, M. hominis, and M. gallisepticum infection after administration of recombinant plasmid vectors expressing melittin gene to BALB/c mice was demonstrated.