The word “antibiotic” literally means “against living things,” since it’s a medicine that kills germs. When we use the term, we practically always refer to drugs that kill bacteria. Medications for other kinds of germs get called “anti-virals,” “anti-fungals,” etc. (see Differences Among Germs).
The first antibiotic, a sulfonamide (“sulfa drug”), was made in 1935 & won a Nobel prize. Penicillin was discovered right around World War II. From then on, more and more were found and invented. There are many classes of antibiotics with differences among them — some work for certain bacteria, and others for others.
Unfortunately, antibiotics aren’t perfect. Bacteria can develop a variety of ways to change their genetic make-up and become resistant to one or another medication. This is happening more and more, due to overuse (like prescribing them for an illness that’s actually caused by a virus), and from adding them to animal feed. We now have very rare instances in which common bacteria have evolved into pan-resistant strains, resistant to everything.
Sometimes patients get into arguments with their medical providers, who often don’t want to prescribe an antibiotic. When you’re sick, and simply want to get better, and know that antibiotics can cure infections, you expect them to prescribe you anything just in case it might work. But for example, 90% of sore throats are caused by viruses, and clinicians have ways to distinguish (see our topic Sore Throat). If we gave antibiotics to everyone, “just in case,” we’d wind up causing lots more harm than good.
If a person is allergic to an antibiotic, we can almost always find another. Studies show that most people who think they’re allergic to penicillin really aren’t. See Allergy.