http://www.rxboomer.com/articles/Antibiotics_Summary.html Antibiotics are substances that inhibit or even kill the growth of bacteria. Even though they were at first extracted from natural sources, today, they are being modified with synthetic chemical elements; they are also known as semi-synthetic antibiotics. You may also read the word antimicrobial referring to antibiotics since some scientists prefer to use antibiotic to refer only to natural substances and antimicrobial for natural and synthetic antibiotics. Penicillin, cephalosporin, fluoroquinolones, and tetracycline are just some few examples of antibiotics, but if you want to know more about these drugs: their usage, dosage and benefits, do not hesitate to read these articles. en-us