Bactenecin is a cyclic antimicrobial peptide isolated from bovine neutrophils with potent activity against Bacterial and Fungal species. IC50 & Target: Bacterial, Fungal^[1] In Vitro: Bactenecin inhibits the growth of Escherichia coli and Staphylococcus aureus at the same concentration. Bactenecin inhibits the growth of other medically important bacteria and yeast, and it kills the fungus Trichophyton rubrum. Acetylation and amidation of the amino- and carboxy-termini of bactenecin do not change its potency, while replacement of its two cysteine residues with serine decreases the potency^[1]. Bactenecin, a dodecapeptide, is strongly cytotoxic to rat embryonic neurons, fetal rat astrocytes and human glioblastoma cells. This neurotoxicity is unique to bactenecin, as a panel of antibacterial peptides from vertebrates and invertebrates, like defensins corticostatin, indolicidin, cecropin P1, tachyplesin I, the magainins, or apidaecins did not impair neuronal viability^[2].