Types of Antibiotics

The origin of the term 'antibiotics' are two Greek words, viz. anti meaning 'against' and bios meaning 'life'. Antibiotics are powerful medicines inhibiting the growth of infection causing bacteria, thereby helping the body fight bacterial infection. They have been used to treat various bacterial infections in plants, animals and human beings, since the 1930s. Antibiotics only fight bacterial infections and do not work against viral infections, such as flu, common cold, sore throat and bronchitis. Antibiotics taken in order to treat viral infections can do more harm to the body, than good. This is because each time the antibiotic dose is taken, the virus is not affected and the chances of emergence of antibiotic resistant bacteria increases. Thus, when an actual bacterial infection occurs, the antibiotic is not able to kill them, as they have become resistant. This is why one should follow the directions given by the doctor carefully while taking antibiotics. Penicillin, the first antibiotic to be discovered, was obtained accidentally by Alexander Fleming from a mold culture. Today, there are over 100 different types of antibiotics that have been identified and are used by doctors to cure mild to severe infections.

Different Types of Antibiotics

Of the 100 plus antibiotic substances produced naturally or synthetically, very few have been proven safe and effective. The commonly used antibiotic types are:

• Penicillins
• Cephalosporins
• Aminoglycosides
• Macrolides
• Sulfonamides
• Fluoroquinolones
• Tetracyclines
• Polypeptides

Penicillins: Penicillins is an antibiotic which destroys the cell walls of the bacteria, while they are in the process of reproduction. Penicillins is a group of bactericidal agents comprising penicillin G, penicillin V, ampicillin, ticarcillin, cloxacillin, oxacillin, amoxicillin and nafcillin. People can be allergic to penicillin, or can even develop rash or fever, due to hypersensitivity towards the antibiotic. Often, penicillins are given in combination with various other antibiotic types.

Cephalosporins: This antibiotic group encompasses bactericidal agents such as cefadroxil, cephapirin, cephradine, cefazolin, cephalexin and cephalothin. Cephalosporins, like the penicillins, interfere with the cell wall formation of the bacteria during reproduction. In cases, where people are sensitive to penicillins, these cephalosporins are administered. However, in most cases, when one is allergic to penicillin, then one is allergic to cephalosporins as well. Rashes and fever are adverse side effects of these antibiotics. The cephalosporin, cefotaxime sodium, is administered to those with severe infections in the bones after surgery.

Aminoglycosides: This type of antibiotic hinders protein formation of bacteria invading cells. This antibiotic encompasses gentamicin, streptomycin and neomycin. As aminoglycosides are effective in inhibiting protein production in invading bacterial cells, they are administered to treat typhus, pneumonia and other bacteria-causing illnesses. However, these antibiotics can enervate kidney and liver functions, and therefore are administered with great deal of caution.

Macrolides: These antibiotics, just like the other types of antibiotics, interfere with the protein formation of invading bacteria. These are commonly administered to treat patients who are highly sensitive towards penicillin. Macrolides encompass azithromycin, clarithromycin and erythromycin. Gastrointestinal discomfort is one of the side effects of these macrolides.

Sulfonamides: These antibacterial agents have been the earliest developed drugs to fight bacterial infections, and are similar to penicillin in their functioning. These drugs are effective in treating kidney infections; however, they do have harmful effects on the kidneys. In order to prevent drug crystal formation, patients are told to drink large quantities of water. One of the most useful sulfa drugs is gantrisin.

Fluoroquinolones: This is the latest class of antibiotics and comprises ciprofloxacin, enoxacin, levofloxacin, norfloxacin and ofloxacin. These antibiotics are considered to be relatively safe and mostly used to treat urinary tract infections. However, it is observed that they affect bone growth, which is why they are not recommended for pregnant women or children.

Tetracyclines and Polypeptides: Tetracyclines are antibiotics used to treat various eye infections and comprise tetracycline, doxycycline and minocycline. On the other hand, polypeptides comprise bacitracin, polymyxin B and colistin. Polypeptides are quite toxic, hence primarily used on the skin surface only.

Doctors prescribe antibiotics based on the type of infection occurring. The most effective antibacterial agent will then be prescribed. Cases, wherein the causative agent is not known, a culture from the infection is sent for identification of the invading bacteria. After identifying the causative organism, the doctor checks the patient's sensitivity to antibiotics and chooses carefully from the various types of antibiotics. The treatment's effectiveness relies on how well the drug gets absorbed into the bloodstream, how much drug enters the body fluids and how fast the body eliminates the drug. Moreover, the choice of an antibiotic also depends on its side effects, allergic reactions and the cost of the drug.