Antibiotics are antimicrobials that kill or inhibit the growth of bacteria. Antibiotics are used to treat infections caused by bacteria.
The word antibiotic comes from the Greek anti meaning "against" and bios meaning "life.
Antibiotics are used for:
The different types of antibiotics are known as classes. Different antibiotics destroy bacteria in different ways and treat different infections. Antibiotics within a class generally have similar effectiveness, mechanism of action and resistance, spectrum of antimicrobial activity, and side effects potential.
Major antibiotic classes include:
Some antibiotics are "bactericidal", meaning that they work by killing bacteria. Other antibiotics are "bacteriostatic", meaning that they work by stopping the growth or multiplication of bacteria.
Penicillin was the first antibiotic re-discovered by Alexander Fleming in 1929 as a natural product produced by Penicillium notatum mold. It is still one of the most useful and important antibiotics.
Penicillins are bactericidal, they kill bacteria by inhibiting the formation of the bacterial cell wall, causing the walls to break down.
Penicillins are used to treat strep throat, tonsillitis, skin infections, urinary tract infections, dental infections, ear infections, gonorrhea. Penicillins are sometimes combined with beta-lactamase inhibitors, which protect the penicillin from bacterial enzymes that may destroy it before it can do its work.
Penicillins are usually very safe. The greatest risk is an allergic reaction, which can be severe.
Cephalosporins are among the most diverse classes, and are divided into generations. Each newer generation of cephalosporins has greater gram negative antimicrobial activity than the preceding one.
Cephalosporins are one of the most widely used antibiotics. Cephalosporins produce bactericidal effect by inhibiting bacteria cell wall formation. They treat a broader range of bacterial infections than penicillins.
Cepha antibiotics are closely related to the penicillins and many people allergic to penicillins also have allergic reactions to cephalosporins.
Cephalosporins are used to treat pneumonia, strep throat, staph infections, tonsillitis, bronchitis, urinary tract infections, otitis media, various types of skin infections, gonorrhea. Cephalosporins are preferred antibiotics for prevention of infection during surgery.
Erythromycin, the first macrolide antibiotic, was discovered in 1952. Macrolides belong to the polyketide class of natural antibiotics and are derived from Streptomyces bacteria.
Macrolides bind with ribosomes from susceptible bacteria to prevent protein production. This action is mainly bacteriostatic, but can also be bactericidal at higher doses.
Newer macrolides, azithromycin and clarithyromycin, are particularly useful for respiratory tract infections because of their high level of lung penetration. Clarithromycin has been widely used to treat Helicobacter pylori infections, the cause of stomach ulcers. Macrolides are very effective against mycoplasma, mycobacteria, and chlamydia.
Macrolides cause very little allergy problems compared to the penicillins and cephalosporins.
Fluoroquinolones (fluoridated quinolones) are broad-spectrum synthetic antibacterials. Nalidixic acid was the first quinolone, introduced in 1962.
Fluoroquinolones are bactericidal. They inhibit bacteria by interfering with their ability to make DNA. This activity makes it difficult for bacteria to multiply.
Fluoroquinolones are prescribed for a variety infections of the respiratory tract, urinary tract, skin, and certain sexually transmitted diseases. Fluoroquinolones have excellent activity against most bacterial causes of infectious diarrhea.
Fluoroquinolones can cause tendinitis and tendon ruptures1. Fluoroquinolones should not be given during pregnancy.
Tetracyclines were discovered in the late 1940s and were extremely popular because their antimicrobial spectrum was broader than of most other antibiotics. Because of the development of bacterial resistance to the tetracyclines, these antibiotics have lost some of their usefulness.
Tetracyclines are bacteriostatic antibiotics that work by inhibiting bacterial protein synthesis.
Tetracyclines are effective against a wide variety of bacteria and are used to treat Rocky Mountain spotted fever, Lyme disease, chlamydia, respiratory tract infections, urinary tract infections, variety of sexually transmitted diseases (STD). Doxycycline is used for prophylaxis of malaria. Minocycline is an alternative to rifampin for elimination the meningococcal carrier state2.
Tetracyclines should not be given to pregnant women and children under 8 years.
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Last updated: March, 2013