Which antibiotics help?
Antibiotics are typically used against bacteria. Therefore, they are well suited for a therapy against bacteria in the blood. However, not every antibiotic is effective against every bacterium.
The widespread use of antibiotics has also led to an increasing spread of antibiotic-resistant strains of bacteria. It is therefore not possible to say clearly which antibiotic should be used against bacteria in the blood. To solve this problem, blood is first drawn from which the bacteria can be isolated and cultured.
Then the resistance of the bacteria can be tested in a laboratory. In this way, the doctor can safely decide which antibiotic is effective in a particular case. If there is not enough time for such a procedure, a calculated or empirical antibiotic therapy can also be carried out. Here, one chooses an antibiotic which is effective against most of the typical pathogens of a disease. It is also important to know through which entry portal the bacteria could probably enter the blood.
Diagnosis
The presence of bacterial pathogens in a patient’s blood is only possible by means of a special laboratory examination, a so-called blood culture, after removal from a venous vessel. The blood culture serves to cultivate any bacteria that may be present in the blood. Ideally, the blood should be drawn at the beginning of a fever increase, as this is usually accompanied by an increase in the concentration of bacteria in the blood, so that the probability of positive and specific detection is greater.
In addition, the sample should be taken several times with a minimum interval of 30 minutes. For this purpose, special sterile bottles are used which contain suitable culture media and the gas mixtures required for the growth of aerobic (with oxygen) or anaerobic (without oxygen) bacteria. As there is usually no knowledge of the pathogen, at least one aerobic and one anaerobic culture bottle are always filled with the patient’s blood.
After collection and transport to a microbiological laboratory, the samples are kept in an incubator at body temperature (approx. 37°C) for several days to allow the growth of possible bacteria in the culture bottle. The presence of bacterial growth is detected by means of special equipment that generates an alarm if even minimal changes in the gas mixture contained in the bottles due to bacterial growth occur.
If the pathogens have been successfully cultured, they can be identified and tested for the presence of possible resistance to antibiotics. When the blood is examined by means of blood culture, false diagnoses can occur if, for example, contamination by skin germs has occurred during the collection of the blood. It is also possible that bacteria are not detected because they are particularly sensitive and therefore cannot survive transport to the laboratory in the culture bottle. In addition, the result can be negative if pre-treatment with antibiotics has already been carried out or if the pathogens causing the disease are not of a bacterial nature.
