streptococcus bacteria
Antibiotics are medicines that are used to fight bacterial infection. For example, penicillin is a common antibiotic that is made from a chemical found in bread mold. It is useful for controlling infections.

Bacteria are single celled organisms that lack a nucleus. Bacteria are all around us and can be both beneficial and harmful to human beings. Our intestines are full of good bacteria that help us to digest our food and absorb nutrients. Cheese, yogurt, chocolate, wine, sourdough bread, beer, kimchee, and sauerkraut are just some of the foods created by bacterial fermentation.

Bacteria can also be bad for us, causing many diseases including some neurological diseases. Bacterial meningitis occurs when a bacterial infection causes the protective membranes surrounding the brain and spinal cord (the meninges) to become inflamed. The first symptoms of bacterial meningitis are suddenly getting a severe headache, stiff and sore neck, and a fever. It is a serious illness that can cause hearing loss, brain damage, or learning disabilities. It can even be fatal.

There are several types of bacteria that can cause meningitis. Childhood immunizations help protect against three of these types of bacteria [Neisseria meningitidis (meningococcus), Streptococcus pneumoniae (pneumococcus), and Haemophilus influenzae type b (Hib)]. Because bacterial meningitis is caused by a bacterial infection, it can be treated with antibiotics.

There are two problems with antibiotics. First, antibiotics can't distinguish between "good" bacteria and "bad" so after taking a round of antibiotics the body is cleaned out of beneficial bacteria. This makes it easier for other bacteria to take over after you stop taking antibiotics.
Secondly bacteria are able to mutate and become resistant to antibiotics. The more widely and constantly an antibiotic is used the more antibiotic resistant bacteria arise.

Antibiotics can be tested using standard microbiology techniques. An agar plate is inoculated with a culture of bacteria. A piece of paper which has been soaked in the experimental antibiotic is placed on the surface. Normally in a few days there would be a sheet of billions of bacteria. If the antibiotics are effective there will be a little ring or halo around the antibiotic disc where the bacteria do not grow. This is called the zone of inhibition. The antibiotic spreads out from the disc with lower and lower concentration. At some point there is not enough antibiotic to kill the bacteria.

 There are compounds found in some plants and fungi that are able to stop bacteria, molds and fungi. Some of these compounds have been made into commercial antibiotics. Some cooking spices such as cinnamon, cloves, garlic, tumeric and cayenne have been used to slow food spoilage.  Scientists are searching the natural world for other natural antibiotics.