Blood Culture

Blood culture is an important microbiological examination, which is performed in suspected septic conditions when bacteria penetrated into patient's blood.


Blood culture means a sample of venous blood that is taken into a special bottle. For better chance of a positive finding, it is advised to repeat the sampling twice or three-times in a time interval. The filled vials are then placed in special culture apparatus, which creates a favorable environment for bacterial growth. Within 2-4 days we are usually able to find out bacterial presence, type of present bacteria and their sensitivity to antibiotics.


Blood is collected for blood culture when we suspect presence of sepsis (blood poisoning). This is a condition when bacteria (and their toxins) penetrate into the bloodstream and spread throughout the body. The source of infection can be virtually anywhere (pneumonia, urinary tract infections, skin infections, phlegmon, bacterial meningitis, infective endocarditis, etc). Blood culture not only confirms the presence of bacteria in patient's blood, but it also helps us to correctly use the most effective antibiotic therapy.


The blood sampling is practically done without any complications. However, for some people it may be a little bit painful. It is important to properly disinfect the skin around the puncture mark to prevent contamination of the blood sample by skin bacteria, which could cause a falsely positive result. In addition, when the blood culture is taken in a patient who is already administered antibiotics, the result may be falsely negative as the presence of antibiotics in the blood sample may prevent the bacteria from multiplication.


Blood culture is a quick and available method of examination in infectious diseases with a more serious course, which is great in confirming the diagnosis and helps to use proper antibiotics.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources