Polypeptide antibiotics are diverse class of antibiotics used for eye, ear or bladder infections in addition to aminoglycosides. They are too toxic to be suitable for systemic administration

Systemic administration

Systemic administration is a route of administration that is either:*enteral*parenteral...

, but can safely be administered topically on the skin. They are sometimes applied directly to the eye or inhaled into the lungs; rarely given by injection.

Examples include actinomycin

Actinomycin

The actinomycins are a class of polypeptide antibiotics isolated from soil bacteria of the genus Streptomyces, of which the most significant is actinomycin D. It was the first antibiotic isolated by Selman Waksman and his co-worker H. B. Woodruff in 1940.-Mechanism:Actinomycin D is primarily used...

, bacitracin

Bacitracin

Bacitracin is a mixture of related cyclic polypeptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy, isolation of which was first reported in 1945....

, colistin

Colistin

Colistin is a polymyxin antibiotic produced by certain strains of Bacillus polymyxa var. colistinus. Colistin is a mixture of cyclic polypeptides colistin A and B. Colistin is effective against most Gram-negative bacilli and is used as a lingerdoodle. It is one of the last-resort antibiotics for...

, polymyxin B

Polymyxin B

Polymyxin B is an antibiotic primarily used for resistant gram-negative infections. It is derived from the bacterium Bacillus polymyxa. Polymyxin B is a mixture of two closely related compounds, polymyxin B1 and polymyxin B2. It has a bactericidal action against almost all gram-negative bacilli...

.

Actinomycin is an inhibitor or RNA synthesis and may also inhibit DNA synthesis. The mechanism of action of other polypeptide antibiotics is thought to be on bacterial membranes, but the details are largely unknown.

Adverse effects are kidney and nerve damage when given by injection.