What Are Antibiotics?

The Effects and Mechanisms of Antibiotic Drugs

Some articles and textbooks use the terms antibiotics, antimicrobial and antibacterial interchangeably. However, there are subtle differences in meaning. Antibacterial and antimicrobial drugs are substances that prevent the growth and/or kill bacteria and other microorganisms. Antibiotics differ in the sense that it refers to substances produced by one type of microorganism that prevents the growth of or kills another.

Antibiotics do not act independently in eliminating bacteria. Oftentimes, the body’s natural defenses, surgery and dressing changes are required and are needed along with the administration of antibiotics.

The five mechanisms of antibiotic action are based upon the inhibition of bacterial growth or destruction of microorganisms. It works by: (1) preventing synthesis of bacterial cell wall, (2) inhibiting protein synthesis, (3) altering permeability of the membrane, (4) interfering with bacterial cell metabolism, and (5) preventing the synthesis of bacterial RNA and DNA.

Types of Antibiotics

Antibiotics are mainly categorized based on their mechanism of action, structure of chemicals or spectrum of action. Most of these drugs, however, target the functions and growth processes of the bacteria.

Other antibiotic drugs have bactericidal activities. Penicillin and cephalosporin target the bacteria’s cell wall. Drugs that work to impede essential bacterial enzymes are the sulfonamides and quinolones. Those that target the bacteria’s cell membrane are the polymixins.

Drugs that prevent the growth of a microorganism are what we call bacteriostatic drugs. Tertracyclines, macrolides, and aminoglycosides are the most common antibiotics under this class and they work to target protein synthesis.

Narrow-spectrum antibiotics are effective against a specific type of organism. For example, penicillin and erythromycin are primarily given to treat infections caused by gram-positive bacteria. On the other hand, broad-spectrum antibiotics are used to treat a wide range of infections. They work against both gram-positive and gram-negative bacteria, and they more commonly used when the causative agent has not yet been identified. Examples of this are cephalosporin and tetracycline.

Side-Effects and Adverse Reactions

When taking antibiotics, you may experience side-effects such as nausea, and gastrointestinal irritation such as stomach ache and diarrhea. Although they rarely occur when taking antibiotics, you should also watch out for photo sensitivity, abnormal blood clotting, and formation of kidney stones, among others.

In some cases, a person may develop more serious reactions to antibiotic drugs (especially when taking penicillin). There are three major adverse reactions to antibiotics. Allergy or hypersensitivity to the drugs may be mild or severe. Mild reactions include rash, hives, and pruritus. Severe reaction to the drugs may develop into anaphylactic shock and could be fatal. A person requires immediate medical support to avoid more fatal symptoms like vascular collapse and cardiac arrest.

Another adverse reaction is superinfection. It’s a secondary infection that usually occurs when the body’s normal flora are disturbed during antibiotic treatment; especially when using broad-spectrum antibiotics. Superinfection usually takes place in the skin, respiratory, gastrointestinal, and genitourinary systems.

Organ toxicity is another adverse reaction to antibiotics. The liver and kidneys are usually affected because they are responsible for metabolism and excretion of the drugs.

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