Broad-spectrum Antibiotics: What They Are For

Broad-spectrum antibiotics are those that act against a wide range of microorganisms. Find out in which cases they are indicated.

Broad spectrum antibiotics are those that act against a wide range of microorganisms. The spectrum refers precisely to the number of microorganisms that are or are not sensitive to the action of the antibiotic.

On the other hand, limited spectrum antibiotics are those that are active only for specific microorganisms. This is not to say that they are less effective than broad-spectrum antibiotics. On the contrary, it is more convenient to use one or the other, depending on the case.

Broad-spectrum antibiotics are the most widely used in the world. Both in humans and animals. Despite their great benefits, they are becoming less and less effective in meeting the infectious challenges of today’s world.

Antibiotics throughout history

Broad spectrum antibiotics

Although there has been a reference to the uses of antibiotics since ancient times, it was in the 20th century when they were understood and began to be used. The discovery of penicillin opened a door to a new world to fight infection.

At the beginning of the 20th century, the average life expectancy was 47.3 years. With the appearance of antibiotics and the purification of water, this figure increased to 75 years, at the end of the same century.

In fact, at present, the infectious map of the world corresponds univocally with the map of availability of antibiotics and drinking water. This gives us an idea of ​​the importance of these drugs.

Broad spectrum antibiotics

Broad-spectrum antibiotics are those that  act on a wide range of gram- positive and gram-negative bacteria. These bacteria have a different structure.

The gram-positive ones are vulnerable to the action of penicillin, whereas the gram-negative ones not so much. The former stain blue or violet by Gram stain, while the latter do not. Hence its name.


The main broad-spectrum antibiotics are tetracyclines, macrolides, and beta-lactams. They are also known as penicillins . These include tetracyclines, macrolides, beta-lactams, cephalosporins, and lincosamides.


They are considered the prototype of broad-spectrum antibiotics. There are natural and synthetic origin. They are used for skin, urogenital, gastrointestinal, respiratory and other infections.


Macrolides are derived from erythromycin. They are used mainly to fight infections of the upper respiratory tract, skin and white tissues. They are especially indicated for patients allergic to penicillins.


Beta-lactams include various penicillin derivatives, cephalosporins, monobactams, carbapenems, carbacephem, and beta-lactamase inhibitors. The broadest spectrum are the fourth generation.


Cephalosporins have a mechanism of action similar to that of penicillins. Those with the broadest spectrum are the fourth and fifth generation. They are effective against gram-positive cocci and against some gram-negative rods.


Lincosamides are especially indicated for alpha and beta hemolytic streptococci, S. pneumoniae and S. aureus.

Uses and applications

Broad-spectrum antibiotics are used primarily when the infectious agents have not been determined with absolute certainty. They are also used in these circumstances:

  • If there is a wide range of possible diseases present. Especially if one of them is potentially serious and can get worse if treatment is delayed.
  • When there are resistant bacteria, they have not responded favorably to the use of limited-spectrum antibiotics.
  • As a prophylactic element after surgery. These antibiotics offer more effective prevention against different types of infections.
  • When a superinfection occurs. In this there are several types of bacteria that cause the disease. This justifies the use of broad-spectrum antibiotics, or a combination of narrow-spectrum antibiotics.

Like all drugs, broad-spectrum antibiotics also pose potential health risks. Hence the importance of administering and using them rigorously following the indications of the case.

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