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The word antibiotic comes from the Greek anti meaning against and bios meaning life (a bacterium is a life form). Antibiotics are also known as antibacterials, and they are drugs used to treat infections caused by bacteria. Bacteria are tiny organisms that can sometimes cause illness to humans and animals.
Antibiotics are among the most frequently prescribed medications in modern medicine. Antibiotics cure disease by killing or injuring bacteria. The first antibiotic was penicillin, discovered accidentally from a mold culture. Today, over 100 different antibiotics are available to doctors to cure minor discomforts as well as life-threatening infections.
Although antibiotics are useful in a wide variety of infections, it is important to realize that antibiotics only treat bacterial infections. Antibiotics are useless against viral infections (for example, the common cold) and fungal infections (such as ringworm).
Before bacteria can multiply and cause symptoms our immune system can usually destroy them. We have special white blood cells that attack harmful bacteria. Even if symptoms do occur, our immune system can usually cope and fight off the infection. There are occasions, however, when it is all too much and our bodies need some help - from antibiotics.
How do antibiotics work?
Although there are a number of different types of antibiotic they all work in one of two ways:
A bactericidal antibiotic kills the bacteria. Penicillin is a bactericidal. A bactericidal usually either interferes with the formation of the bacterium's cell wall or its cell contents.
A bacteriostatic stops bacteria from multiplying.
Antibiotics work by being either bactericidal where they kill microorgnisms; or by being bacteristatic where they inhibit the growth of the microorganisms.
An example of a bactericidal antibiotic is Penicillin. This works by preventing the production of a substance that forms the cell wall: peptidoglycan. This means the cell will continue to grow without dividing or developing new cell wall. Therefore, the wall gets weaker, and eventually ruptures.
What are antibiotics for?
An antibiotic is given for the treatment of an infection caused by bacteria. They target only bacteria - they do not attack other organisms, such as fungi or viruses. If you have an infection it is important to know whether it is caused by bacteria, and not a virus or fungus. Most upper respiratory tract infections, such as the common cold and sore throats are generally caused by viruses - antibiotics do not work against viruses.
If antibiotics are overused or used incorrectly there is a chance that the bacteria will become resistant - the antibiotic becomes less effective against that type of bacterium.
A broad-spectrum antibiotic can be used to treat a wide range of infections.
A narrow-spectrum antibiotic is only effective against a few types of bacteria. There are antibiotics that attack aerobic bacteria, while others work against anaerobic bacteria. Aerobic bacteria need oxygen, while anaerobic bacteria don't.
Antibiotics may be given beforehand, to prevent infection, as might be the case before surgery. This is called 'prophylactic' use of antibiotics. They are commonly used before bowel and orthopedic surgery.
Types of Antibiotics
Although there are well over 100 antibiotics, the majority come from only a few types of drugs. These are the main classes of antibiotics.
Penicillin such as penicillin and amoxicillin
Cephalosporin such as cephalexin (Keflex)
Macrolides such as erythromycin (E-Mycin), clarithromycin (Biaxin), and azithromycin (Zithromax)
Fluoroquinolones such as ciprofloxacin (Cipro), levofloxacin (Levaquin), and ofloxacin (Floxin)
Sulfonamides such as co-trimoxazole (Bactrim) and trimethoprim (Proloprim)
Tetracyclines such as tetracycline (Sumycin, Panmycin) and doxycycline (Vibramycin)
Aminoglycosides such as gentamicin (Garamycin) and tobramycin (Tobrex)
Each antibiotic is effective only for certain types of infections and your doctor are best able to compare your needs with the available medicines. Also, a person may have allergies that eliminate a class of antibiotic from consideration, such as a penicillin allergy preventing your doctor from prescribing amoxicillin.
Although antibiotics are generally considered safe and well-tolerated, they have been associated with a wide range of adverse effects. There are various side-effects that can be very serious depending on the antibiotics used and the microbial organisms targeted.
Antibiotics may have side effects. Some of the more common side effects may include:
Mild stomach upset
Feeling and being sick
Fungal infections of the mouth, digestive tract and vagina
You should notify your doctor if you have any of the following side effects:
Severe watery diarrhea and abdominal cramps
Allergic reaction (shortness of breath, hives, swelling of your lips, face, or tongue, fainting)
Vaginal itching or discharge
White patches on your tongue
Use of all antibiotics may temporarily reduce the effectiveness of birth control pills; alternative birth control methods should be used while taking these medications. Antacids should be avoided while on tetracyclines as the calcium can impair absorption of this antibiotic class. For this reason, tetracyclines should not be taken just before or after consuming foods rich in calcium or iron. Consult specialized references for additional interactions to specific antibiotics.
Current Issues in Medicine and Antibiotics
One of the foremost concerns in modern medicine is antibiotic resistance. Simply put, if an antibiotic is used long enough, bacteria will emerge that cannot be killed by that antibiotic. This is known as antibiotic resistance. Infections exist today that are caused by bacteria resistant to some antibiotics. The existence of antibiotic-resistant bacteria creates the danger of life-threatening infections that don't respond to antibiotics.
There are several reasons for the development of antibiotic-resistant bacteria. One of the most important is antibiotic overuse. This includes the common practice of prescribing antibiotics for the common cold or flu. Even though antibiotics do not affect viruses, many people expect to get a prescription for antibiotics when they visit their doctor. Although the common cold is uncomfortable, antibiotics do not cure it, nor change its course. Each person can help reduce the development of resistant bacteria by not asking for antibiotics for a common cold or flu.
Antibiotic resistance arises as a result of natural selection. Since bacteria reproduce rapidly, resistance can arise quickly. Those antibiotics resistant will remain after treatment and can continue to divide.
An example of antibiotic resistance can be seen with Penicillin, some bacteria can produce an enzyme called Penicillinase which breaks down Penicillin before it can take effect.
Other mechanisms of resistance include the evolution of a capsule that is resistant to antibiotic, and cell membranes becoming less permeable to antibiotic.
Bacteria can spread resistance genes between each other by bacterial conjugation where two cells join by their pilli and exchange plasmids which often contain genes for antibiotic resistance.
Antibiotic resistance is made much worse by the overuse of antibiotics in medical treatment. Some bacteria are resistant to most antibiotics (MRSA or mycobacterium-tuberculosis) meaning it is increasingly difficult to treat infection unless new antibiotics are developed.