How do antibiotics work? When is it appropriate to take them?

Antibiotics cure diseases by killing bacteria or blocking their multiplication and are among the most commonly prescribed medicines.

The first antibiotic to be used was penicillin, which was accidentally discovered by Alexander Fleming in his St. Martin laboratory in London.

Today, over 100 types of antibiotics are available for infection treatment.

Although antibiotics are used for a variety of infections, it is important to know that they can only be used to treat bacterial infections. Antibiotics are ineffective against viral infections (for example, the common cold) and fungal infections (for example, Tinea).


How do antibiotics work?

The job of antibiotics is to kill bacteria; these are single-celled organisms that multiply in our body and cause diseases.
Some bacteria produce chemical substances that can damage certain parts of our organism. In an ear infection, for example, the bacteria attack the inner ear, and as the body fights back against the damaging cause, the natural processes of the immune system lead to inflammation.
In this case, it is necessary to take a specific antibiotic to kill the bacteria and eliminate the inflammation.
An antibiotic is therefore a selective “poison”. It must be chosen to kill the dangerous bacteria without harming the cells of our body. Each type of antibiotic affects certain bacteria in different ways. For example, they can inhibit a bacterium’s ability to convert glucose into energy or interfere with its ability to build a cell wall. When this happens, a bacterium dies instead of multiplying. The antibiotic only acts on the life mechanisms of the bacterium and not the normal cells.

How to take antibiotics?

The doses of the antibiotic can be taken in different ways: by oral route (tablets and capsules or syrup), in local application (cream, lotion, spray or drops), by injection (by intramuscular injections or via an infusion directly into the blood).
The chosen form depends on the type of infection. Topical antibiotics are often used to treat skin infections, while antibiotics taken orally are used to treat much of the mild to moderate infections.
Injections or infusions are usually intended for serious infections and are usually done in the hospital.
It is important to continue the treatment as prescribed, even if you feel better again, unless the doctor says otherwise. Because if the intake of the antibiotic is stopped prematurely, the bacteria can become resistant.


The ability of antibiotics to cure previously incurable infectious diseases has led to an often unjustified use of this drug. In most European countries, antibiotics are the most widely used drugs and are second only to analgesics.
Unfortunately, their excessive and inappropriate use in human medicine, veterinary medicine and agriculture has led to a rapid increase in drug-resistant microorganisms. Many of the first antibiotics became ineffective and are much less reliable than before.

Antibiotic resistance results from the transfer of the characteristics of genetic resistance among bacteria of the same or different species. By and large, the more a specific antibiotic is used, the greater the risk that it will lead to phenomena of resistance to the same antibiotic, which will then render the drug less and less effective.
To prevent this development of resistance, new antibiotics with similar but not identical chemical characteristics were developed, which remained effective until renewed signs of resistance appeared.
It has therefore become essential to develop new antibiotics in order to have an effective treatment against particularly aggressive bacterial infections.

When is it appropriate to take antibiotics?

Antibiotics are effective against bacterial infections. However, they do not work against viruses, fungi and parasites.
Taking antibiotics for a viral infection does not treat the disease and only increases the possibility of resistance.
The basic rules to be followed – regardless of the type of infection – which are derived for the proper use and maximum benefit of the antibiotic without creating a risk for the development of resistant microorganisms, are essentially three:

  • take only if they are actually useful, and only as indicated by the doctor;
  • use the right antibiotics, in the right dosage, throughout the period of their prescription;
  • refrain from “self-prescribed” applications, even if you think you know exactly how to use them in treatment.

Against colds, antibiotics help little or not at all.
Influenza and symptoms of parainfluenza, runny nose, sore throat and earache are almost always caused by viruses and not by bacteria.
The only effective strategy for flu is to keep calm in an appropriate environment, drink a lot, eat a light diet, eat fruits and vegetables to fortify vitamins, and antipyretic agents for fever.
Antibiotics can only be recommended by the doctor in special cases, for example if you suffer from chronic diseases of the respiratory tract or the cardiovascular system, in order to prevent or treat possible bacterial secondary infections favored by the flu (especially pneumonia).
With a cold, antibiotics do not help. If the symptoms are pronounced, decongestant nasal drops can be used for 4-5 days.

Also, sore throats are in most cases caused by a virus and can be treated with local decongestants.
Only in the case of severe symptoms together with fever, which persists for 2-3 days despite antipyretic medication, intervention with antibiotics may be necessary.
Coughing can only be one of the flu symptoms or its own clinical picture.
In the first case, means are sufficient for therapy, which serve to calm (cough suppressant) or eliminate excessive bronchial mucus (cough removers or expectorants). Antibiotics can be used if there is a risk of bacterial infection of the bronchi or lungs.

Read more: