Effects of Penicillin

Penicillin is a form of antibiotic capable of inhibiting the growth of other organisms. Penicillin was discovered in 1928 by Alexander Fleming after culturing Staphylococcus aureus and noticing its inhibition by unknown spores. Since that time, more than 3,000 antibiotic types have been discovered. Antibiotics are formed from microorganisms, plants and animals, but only a small percentage of them are used in medicine. Penicillin is in a category called beta-lactams, and it is one of the oldest used antibiotics.

Structure

• Penicillin antibiotics are formed from the covalent bonds of the amino acids cysteine and valine. The most potent of the penicillin antibiotic class is penicillin G. Even though it is the strongest of the derivatives, it has shortcomings like other penicillin classes. These antibiotics are only strong against gram positive bacteria, absorb poorly into the blood stream and some bacteria have developed enzymes that inactivate the drug. Overuse of penicillin is one reason why even a highly effective antibiotic loses potency.

Mode of Action

• Penicillin antibiotics are effective against bacteria through reactions that inhibit the growth of the microbe's cell wall. When bacteria are unable to create a properly formed cell wall, fluids are able to enter the cell causing it to burst. This is the mode of action used by penicillin to destroy bacteria in the human body.

Mechanism

• Gram positive bacteria have a thick cell wall made mostly of cellulose and sugar units. The cellulose and polysaccharides are cross linked to form a mesh with a solid backbone. Before the bacteria are able to create the backbone mesh, penicillin inhibits the enzyme that catalyzes the reaction and replaces the final compound with a faulty amino acid. The replacement is irreversible, so the bacterium cell is unable to protect its inner cell structure from osmotic pressure. Water rushes in the cell, the cell wall bursts and the cell is destroyed. Additionally, since animal and human cells do not have a cell wall, penicillin only affects bacteria and not the host.

Resistance

• Bacteria cells mutate often, so the invention of penicillin has created resistant strains of bacteria. Bacteria have developed penicillinases, enzymes that destroy the bond in the active ring of penicillin rendering it inactive. The adaptation of bacteria against penicillin has also made some bacteria resistant against other kinds of antibiotics as well.

Allergies

• An estimated 300 to 500 people die every year from penicillin allergies. Patients who are allergic to penicillin experience anaphylactic shock, an acute condition that causes blood pressure to drop, airway inflammation and a weak pulse. The reaction is from penicillin binding to immune receptors in the body and eliciting an IgE-mediated inflammatory response.