Susceptibility of Neisseria gonorrhoeae to protegrins.

We developed a sensitive and quantitative radial diffusion method to ascertain the susceptibility of six strains of Neisseria gonorrhoeae to antimicrobial peptides derived from mammalian leukocytes. The test organisms included the well-characterized serum-resistant FA19 and serum-sensitive F62 strains plus four antibiotic-resistant clinical isolates. Although each N. gonorrhoeae strain was resistant to human neutrophil defensins, all six were exquisitely sensitive to protegrins, a family of small beta-sheet antimicrobial peptides recently identified in porcine leukocytes. Protegrin-treated N. gonorrhoeae became vacuolated and had striking membrane changes when viewed by transmission and scanning electron microscopy. Because low concentrations of protegrins can also inactivate Chlamydia trachomatis and human immunodeficiency virus, they show promise for development as topical agents to avert sexually transmitted diseases.