Polypeptide antibiotic

Polypeptide antibiotics are a chemically diverse class of anti-infective and antitumor antibiotics containing non-protein polypeptide chains. Examples of this class include actinomycin, bacitracin, colistin, and polymyxin B. Actinomycin-D has found use in cancer chemotherapy. Most other polypeptide antibiotics are too toxic for systemic administration, but can safely be administered topically to the skin as an antiseptic for shallow cuts and abrasions.

Actinomycin-D is believed to produce its cytotoxic effects by binding DNA and inhibiting RNA synthesis. Other polypeptide antibiotics are thought to act by permeabilizing the bacterial cell membrane, but the details are largely unknown.

Animal studies have shown that actinomycin-D is corrosive to skin, irritating to the eyes and mucous membranes of the respiratory tract, and highly toxic by the oral route. It has also been shown to be carcinogenic, mutagenic, embryotoxic and teratogenic. Adverse effects of other polypeptide antibiotics include kidney and nerve damage when given by injection.

Polypeptide antibiotics are produced by all living organisms; largely by bacteria and generally function as natural host defence, presenting new medicinal opportunities. These antibiotics act via permeabilising the bacterial cell membrane, or neutralising its toxicity to cause cell death in bacteria. Its predominant clinical use is as a topical medication, however successful laboratory trials are limited. A common polypeptide antibiotic is bacitracin, derived from the bacteria Bacillus licheniformis. As a therapeutic drug, it has minimal harmful effects and low toxicity, however side effects in patients may include minor skin irritation and anaphylaxis in severe cases.

The development of new polypeptide antibiotics are used as an alternative drug therapy for patients with resistance to more commonly used medications. However further research is required to support the safety of use, and the biological response of the human body to polypeptide antibiotics.