Antibiotics: classification and uses

An antibiotic is a chemical produced by or derived from microorganisms (i.e. germs such as bacteria and fungi or bugs). Antibiotics are among the most frequently prescribed medications in modern medicine. Antibiotics cure disease by killing the bacteria or by bacterial reproduction and growth inhibition. Some antibiotics can be used to treat a wide range of infectious diseases and are known as "broad-spectrum" antibiotics. Others are only effective against a few types of bacteria and are called "narrow-spectrum" antibiotics.

Bacterial resistance

The treatment of infectious disease is compromised by the development of antibiotic-resistant strains of microbial pathogens. Antibiotic-resistant bacteria are germs that cannot be killed by commonly used antibiotics. When bacteria are exposed to the same antibiotics over and over, a variety of biochemical processes occur within these bacteria. These processes may keep antibiotics out of the cell, alter the target of the drug, or disable the antibiotic allowing bacteria to change and no longer be affected by this drug.

The rapid spread or development of antibiotic resistance may compromise standard empiric treatment of many infectious diseases. Resistant bacteria do not respond to the antibiotics and continue to cause infection. Indeed, the greatest threat to successful antibiotic coverage, and hence the driving force behind the search for new therapies, is the evolution and spread of antibiotic resistance.

Beta-lactamases are enzymes produced by some bacteria and are responsible for their resistance to beta-lactam antibiotics like penicillins, cephalosporins, cephamycins and carbapenems. Beta-lactam antibiotics are mainly used to treat a broad spectrum of gram positive and gram-negative bacteria.

Often beta-lactam antibiotics are combined with bacterial beta-lactamase inhibitors in order to be able treat infections caused by bacteria resistant to beta-lactam antibiotics (for example ampicillin/sulbactam, ticarcillin/clavulanate, amoxicillin/clavulanic acid, piperacillin/tazobactam, etc). Nowadays these combined drugs are called next generation antibiotics.

Types of antibiotics

There are many different types of antibiotics. The type of prescribed antibiotics depends on the type of infection and what kinds of antibiotics are known to be effective.

The main classes of antibiotics include:
•    Macrolides
•    Aminoglycosides
•    Cephalosporins
•    Fluoroquinolones
•    Penicillins
•    Tetracyclines
•    Carbapenems


Macrolides

Macrolides are erythromycin-like antibiotics. They are used to treat respiratory tract infections, genital, gastrointestinal tract, soft tissue infections caused by susceptible strains of specific bacteria. Some of the more recent additions to the macrolide group are azithromycin and clarithromycin. They work the same way as the other macrolides, but typically are more effective with fewer side effects.