Bacitracin: Effects, Uses & Risks

Bacitracin is an antibiotic that inhibits cell wall synthesis in some bacteria. The drug has been shown to be effective against Gram-positive bacteria and against Neisseria.

What is bacitracin?

Bacitracin is a drug in the polypeptide antibiotic drug class. Antibiotics are drugs used to treat bacterial infectious diseases. Bacitracin is a drug of the polypeptide class of antibiotics. Antibiotics are drugs used to treat bacterial infectious diseases. Together with agents against diseases caused by protozoa, against viruses, against worms and against fungi, they form the group of anti-infectives. Polypeptide antibiotics act directly in the cell membrane of bacteria. In addition to bacitracin, polymyxins and tyrothricin also belong to the group of polypeptide antibiotics. The active ingredient of bacitracin is extracted from the pathogen Bacillus subtilis. Bacillus subtilis is a bacterium of the Bacillaceae family.

Pharmacological action

Bacitracin interferes with the cell wall structure of certain bacteria. The cell wall of bacteria is composed of organic polymers. It is located outside the cell plasma membrane. The polypeptide antibiotic forms a complex with undecaprenyl diphosphate. Undecaprenyl diphosphate is a carrier lipid that participates in cell envelope synthesis of Gram-negative and Gram-positive bacteria. The formation of the complex inhibits another lipid carrier, bactoprenol. This substance is required by bacteria for the transport of sugar molecules used for the bacterial murein layer. Murein is also known as a peptidoglycan. The peptidoglycan shell serves to stabilize the bacteria. It builds a counterbalance to the osmotic pressure found inside the bacterium. If the murein layer is dissolved or cannot build up properly, the bacterium will burst. Bacitracin is thus a bactericidal antibiotic. Bactericidal antibiotics can induce cell death of pathogens. Bacteriostatic antibiotics, on the other hand, only inhibit the growth and multiplication of bacteria. However, they cannot kill dormant pathogens.

Medical application and use

Bacitracin is available only in the form of an ointment. It is applied to the infected areas of the skin. Indications for the use of Bacitracin are infections with Gram-positive pathogens. Gram-positive pathogens are bacteria that stain blue in the so-called Gram stain. In contrast to Gram-negative bacteria, Gram-positive bacteria have a distinct peptidoglycan layer of murein. They have no additional outer cell membrane. Known Gram-positive pathogens are staphylococci and enterococci. Staphylococci are spherical bacteria that can multiply aerobically or anaerobically. Staphylococci include pathogens such as Staphylococcus epidermidis, Staphylococcus aureus, Staphylococcus capitis, and Staphylococcus hominis. Enterococci are also known as group D streptococci. They occur in large numbers in the intestines of animals and humans. Enterococci are generally rather low pathogenic. However, they are frequently involved in mixed infections. Infections caused by enterococci or staphylococci and treated with bacitracin include, for example, infections of the external ear. In such otitis externa, the skin in the area of the external auditory canal is inflamed. Bacitracin is also used as an eye ointment for inflammations of the eye. Inflammation of the sinuses can also be treated with Bacitracin. If necessary, the ointment can also be applied prophylactically to wounds after operations. In this way, infections can be prevented.

Risks and side effects

Bacitracin should not be used for viral infections, for fungal infections, or for tuberculous infections. Ear infections associated with perforation of the tympanic membrane are also a contraindication. Ulceration of the cornea and stromal injury are also contraindications. Local reactions in the form of allergic contact dermatitis may occur with the use of bacitracin. Allergic contact dermatitis is an inflammation of the skin caused by a type IV allergy. Contact with the allergen in the ointment sensitizes the patient’s T lymphocytes. When the antibiotic ointment is applied again, the inflammatory skin change forms with a delay of one to three days.The acute form progresses in four stages. The affected skin areas are initially very red and swollen. Then blisters and pustules form. These usually burst open very quickly and ooze. After drying out, crusts and / or scales develop from the burst blisters. With repeated irritation by the bacitracin, the eczema does not heal but becomes chronic. As a complication, superinfection with viruses or other bacteria may occur.