Introduction – What is a broad spectrum antibiotic?
An antibiotic is a substance used against bacteria. Antibiotics reduce the metabolic activity of the bacteria and thus lead to a reduced reproduction of the bacteria, which can prevent the survival of a bacterial colony. Broad-spectrum antibiotics (also known as broad-spectrum antibiotics), as the name suggests, have a broad spectrum of activity.
They can therefore be used for a particularly large number of different groups of bacteria. The individual types of bacteria have many different defence mechanisms and differ in their metabolic properties. Broad-spectrum antibiotics can override the various defence mechanisms of the bacteria with their mechanism of action and thus kill many different types of bacteria.
Indications
The indications for the use of broad-spectrum antibiotics are manifold. These versatile drugs are substances that can be used in many infectiological areas. For example, a broad-spectrum antibiotic is typically administered in the case of an infection where the exact pathogen is not yet known.
For example, if a person with pneumonia or a urinary tract infection needs to be treated, a broad-spectrum antibiotic is first selected. In most cases, the symptoms will improve, as the broad-spectrum antibiotic is very likely to kill the underlying germ. In outpatient treatment, a broad-spectrum antibiotic is often chosen that is most effective against the type of bacteria that are most common in the disease being treated.
If an affected person is treated in hospital, blood samples and samples from the infected areas of the body are usually taken. From this, a so-called culture is obtained in which the infecting bacteria grow. Then it can be tested which antibiotics work best.
As this process takes a few days, affected persons are first treated with a broad-spectrum antibiotic. Once the exact bacteria have been detected, the treatment can be switched to a more specific antibiotic. Broad-spectrum antibiotics are also used in all areas in which people with a weakened immune system.
In oncology, for example, several broad-spectrum antibiotics are often given simultaneously under chemotherapy. People affected by chemotherapy have a very weak immune system. In order to prevent bacterial infections of all kinds, antibiotics are used that are effective against as many pathogens as possible.
Broad-spectrum antibiotics can also be used in other areas with immunosuppression (reduced function of the immune system). Thus, people with chronic inflammatory diseases are often treated immunosuppressively. Bacterial infections are also common after transplantations or cortisone therapies, which is why broad-spectrum antibiotics are used in these areas.
Active ingredient and effect
Broad-spectrum antibiotics cannot be reduced to a specific active substance or to a specific mode of action. There are many different broad-spectrum antibiotics, and none of them is effective against all types of bacteria. Even a broad-spectrum antibiotic must be chosen so that the most likely underlying bacterial species can best be controlled with the antibiotic.
Broad-spectrum antibiotics include aminopenicillins (amoxicillin, ampicillin), which prevent the bacteria from forming a cell wall and thus kill the germs. The group of cephalosporins (ceftriaxone, cefotaxime, ceftazidime) also inhibit cell wall formation, as does the group of carbapenems (meropenem). In addition, the different classes of active ingredients can disable additional defence mechanisms of the bacteria.
Carbapenems, for example, are beta-lactamase resistant. Beta-lactamase is an enzyme of the bacteria which forms a special defence mechanism against some antibiotics. However, the beta-lactamase-resistant broad-spectrum antibiotics cannot be prevented from working by this enzyme.
The group of fluoroquinolones (ciprofloxaxin, levofloxacin), on the other hand, has a different mechanism of action: these broad-spectrum antibiotics inhibit the so-called bacterial gyrase. This is also an enzyme of the bacteria. The bacteria need the gyrase to read the information from their own cell blueprint (the DNA) that is needed to build new cells.
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