Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Penicillin is a group of antibiotics derived from Penicillium fungi. Penicillin antibiotics are historically significant because they are the first drugs that were effective against many previously serious diseases, such as syphilis, and infections caused by staphylococci and streptococci. Penicillins are still widely used today, though many types of bacteria are now resistant. Learn more about the penicillin antibiotics in the following pages.