Quiz: How Much Do You Know About Antibiotics?

Antibiotics kill bacteria or keep them from growing. They don't fight viruses, like those that give you a cold or the flu. If you don't take them properly, these drugs may cause the bacteria to change, which makes antibiotics less likely to work. That's called resistance.

Some studies suggest that triclosan, which is in many antibacterial soaps and cleansers,could lead to changes in bacteria that make antibiotics less able to fight them. The FDA wants companies that make these soaps to show more proof that they work. The agency says there is no evidence that they are better at preventing illness than plain soap and water.

Doctors often prescribe antibiotics to treat acne. Any antibiotic you take -- no matter what it’s for -- can cause resistance. Work closely with your doctor to find the best treatment for you.

Strep throat is caused by bacteria. You need a lab test to know for sure if you have it.

A sinus infection, also called sinusitis, is almost always caused by a virus or by irritation from the air. The infection gets better on its own without antibiotics. Although it's rare, some sinus infections are caused by bacteria. If your symptoms last for more than 10 days after you see a doctor, schedule a follow-up.

A virus or bacteria can cause ear infections. They may get better without antibiotics. Your doctor may consider several things to help decide whether to use them, including how old or sick you are. He may wait a couple of days to see if your symptoms go away.

Take them exactly as your doctor tells you to. Don't skip doses, and finish them all. If you stop too soon, some bacteria may survive and make you sick again.

These conditions are all caused by bacteria and have long been treated -- and generally cured -- with antibiotics. But that’s changing. They’re becoming antibiotic resistant. Scientists have found several strains of gonorrhea that don’t respond to any antibiotic. Resistant forms of chlamydia and syphilis aren’t as common, but they do exist.

These infections include things like tuberculosis, skin problems, and sexually transmitted diseases. People get most of them at home, school, or work. But you can catch some in health care settings like hospitals or nursing homes. You might pick up the bacteria from surfaces or from the hands of doctors or nurses.

Livestock that get antibiotics can develop resistant bacteria in their bodies. If you eat meat from them that isn’t cooked or handled right, that bacteria can get into you. Fertilizer and water used on crops can also spread bacteria. The FDA says it’s phasing out the use of antibiotics, except those prescribed by a veterinarian, in animals raised for food.

Researchers haven't developed a major class of antibiotics since the 1980s. The threat of resistance has been around for decades, though. In his Nobel Prize speech in 1945, Alexander Fleming, who discovered penicillin, warned that antibiotics could become less effective. But efforts are now under way to create more -- teixobactin is an example of a recently discovered antibiotic.

It takes an economic toll on the whole health care system. Resistant infections make people sicker. They stay in the hospital longer and need more expensive treatment.

It causes life-threatening diarrhea. Each year, about half a million people get C. diff and 15,000 die. The bacteria are naturally resistant to many drugs and spread quickly.

Carbapenem-resistant enterobacteriaceae (CRE) is also considered an urgent threat. It causes infections that are resistant to nearly all antibiotics. Those include carbapenems, commonly considered a last resort.

A third urgent threat is drug-resistant Neisseria gonorrhoeae, which causes gonorrhea.

MRSA and drug-resistant tuberculosis are considered to have a threat level of "serious."

Someone else's medicine may not be the right one for your illness. If you take the wrong kind, it might slow down your recovery. It could even make you get worse.