Antimicrobial Cationic Peptides: Small cationic peptides that are an important component, in most species, of early innate and induced defenses against invading microbes. In animals they are found on mucosal surfaces, within phagocytic granules, and on the surface of the body. They are also found in insects and plants. Among others, this group includes the DEFENSINS, protegrins, tachyplesins, and thionins. They displace DIVALENT CATIONS from phosphate groups of MEMBRANE LIPIDS leading to disruption of the membrane.Peptides: Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are linear polypeptides that are normally synthesized on RIBOSOMES.Magainins: A class of antimicrobial peptides discovered in the skin of XENOPUS LAEVIS. They kill bacteria by permeabilizing cell membranes without exhibiting significant toxicity against mammalian cells.Polymyxin B: A mixture of polymyxins B1 and B2, obtained from Bacillus polymyxa strains. They are basic polypeptides of about eight amino acids and have cationic detergent action on cell membranes. Polymyxin B is used for infections with gram-negative organisms, but may be neurotoxic and nephrotoxic.Anti-Bacterial Agents: Substances that reduce the growth or reproduction of BACTERIA.Defensins: Family of antimicrobial peptides that have been identified in humans, animals, and plants. They are thought to play a role in host defenses against infections, inflammation, wound repair, and acquired immunity.Anti-Infective Agents: Substances that prevent infectious agents or organisms from spreading or kill infectious agents in order to prevent the spread of infection.Cations: Positively charged atoms, radicals or groups of atoms which travel to the cathode or negative pole during electrolysis.Microbial Sensitivity Tests: Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).beta-Defensins: DEFENSINS found mainly in epithelial cells.Histatins: A group of small, histidine-rich, cationic peptides in human SALIVA which are antibacterial and antifungal.