How do antibiotics work?

Billions of antibiotics are prescribed every year for all sorts of common ailments; acne, staff infections, urinary tract infections, sinus infections. I would venture to guess that few patients question how the antibiotic does its job, how that particular antibiotic is chosen or how safe their antibiotic is.

The basic idea of how an antibiotic works is simple. Antibiotics target bacterial cells for eradication. This begs the question, how to antibiotics distinguish between a healthy human cell and a bacterium? That is, why don't antibiotics kill the patient as well as the bacteria?

There are certain processes that are unique to bacterium. Antibiotics are chosen for their ability to target these bacteria specific processes. Different antibiotics target different processes.

Penicillin targets Peptidoglycan, a macromolecule found in the cell wall of bacteria. The group of antibiotics known as Sulfas interupt metabolic pathways within a bacteria cell by preventing the production of folic acid. Folic acid is required by all cells for proper growth and development. Without this macromolecule, the cell dies. Tetracycline, an antibiotic commonly prescribed for acne, is able to interupt protein synthesis within a bacterial cell. Yet another common antibiotic, Ciprofloxacin, is able to target an enzyme within bacterium, which interupts DNA replication.

Selecting compounds that only attack bacterium is crucial to the safety of antibiotics. Without an understanding of the similarities and differences between the cells of bacteria and those of humans and other animals, we could not effectively use antibiotics to fight infection.