Antibiogram is performed before antibiotic treatment in order to make the antibiotic therapy effective. Treatment should take into account the sensitivity of the bacteria to the antibiotic. And the rate at which resistant bacterial strains emerge means fewer and fewer antibiotics are able to fight the infection. What does an antibiogram look like? How long does the examination take? How to interpret the results of an antibiogram?

Antibiogramtomicrobiological testto determine which antibiotics are resistant to bacteria and to which they are sensitive. Based on the results of the antibiotic, you can give the patient a specific type of antibiotic that fights the bacteria that is the cause of the infection, and thus - maximize the effectiveness of antibiotic therapy.

When is an antibiogram taken? Indications for an antibiogram

There is now an unhe althy tendency for patients to take large amounts of antibiotics often unnecessarily, with the result that more and more bacterial strains become resistant to these types of drugs. Therefore, antibiograms are performed mainly in the case of severe or recurrent infections, where it is not known exactly which bacteria have attacked the body and which drugs are resistant to. In order not to administer to the patient ineffective antibiotics, which will only weaken the patient's immune system, an antibiogram should be performed. Antibiogram is also performed when it is known that a given pathogen is not very sensitive to antibiotics.

Antibiogram - how to prepare for the test?

When blood is collected or urinated, it is advisable that the patient is on an empty stomach. If a swab is to be taken from the throat, local medications should not be used for several days before the examination as they may alter the test result.

What does an antibiogram look like?

The first stage of the test is to collect a sample of secretions from the patient, e.g. blood or sputum, which are then inoculated on a bacteriological medium, i.e. the collected bacteria are grown on special media. After several hours, if there was a bacterium in the patient's secretion, it will grow on the substrate. The characteristic features of a given bacterium are color, shape and other properties.

The second stagethe antibiogram is a study of the growth of the bacteria grown in the presence of several or a dozen cotton discs, each of which is soaked with a different antibiotic. After 18-24 hours of incubation at 37 ° C, you can see which antibiotic discs best de alt with the bacteria around them. A zone of inhibition of bacterial growth is created around each disc. The greater it is, the greater is the sensitivity of the strain to a given antibiotic, and the lower it is, the greater the resistance of the strain. In this way, information is obtained which antibiotics are effective in the fight against a given bacterium. This is the most common type of antibiogram, the so-called antibiogram performed by disc diffusion on agar.

In laboratories, it is also possible to perform an antibiotic dilution method in a liquid or solid medium, or by an automatic method - the machines themselves apply the bacterial sample to plates containing antibiotics in various concentrations. The results of these studies are compiled and annotated by a computer system.

How to read the antibiogram result?

After receiving the results of the tests that were carried out with the disc method, the doctor may define the bacterial strain as sensitive, intermediate, or resistant. The final type is determined by comparing the inhibition zone diameter to the cut-off diameters, which were established by the Comité de l'Antibiogramme de la Societé Française de Microbiologie (Committee for Antimicrobial Susceptibility Testing of the French Society of Microbiology).

  • susceptible strain - you can give the patient antibiotics in traditional doses
  • intermediate susceptible strain is treated with antibiotics, but only when increased doses of the drug are administered
  • resistant strain does not respond to treatment regardless of the treatment method and doses applied

Is the antibiogram effective?

Antibiogram cannot be 100% certain to which type of antibiotic a given bacterium is susceptible to. Doubts arise especially with a throat swab. Microorganisms are organisms that are very sensitive to the medications used by the patient, e.g. aerosols, gargle rinses, tablets, which may inhibit their growth locally. Then it is difficult to grow bacteria from the material collected for the swab, despite the fact that the infection in the body is still going on.

Important

If the patient wants to avoid treatment with an unsuccessful and sometimes expensive antibiotic, and the doctor does not want to refer for the examination, he can go to the bacteriological laboratory himself. The examination is payable and costs PLN 50.

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