Consultant Pediatrician – B.J.Wadia Hospital for Children
Editor - Pediatric Oncall
What is blood culture?
Normally, blood is free of various germs. In case of serious infections, there may be germs circulating in the blood. By incubating blood collected in various agents, one can check for growth of bacteria and viruses and thus identify the germ causing the infection. This checking of blood for growth of germs is called blood culture.
How is blood culture done?
Blood is collected after through cleaning of skin with spirit and iodine with a needle and syringe (to prevent contamination from skin germs) and then blood is transferred to a culture bottle. This culture bottle is incubated over 2-10 days to look for growth of bacteria and identify the type of bacteria. The quantity of blood collected for culture may appear to be more but it is important that enough blood is drawn so that culture reports are accurate.
Why are sometimes 2 or 3 blood cultures done?
A blood culture helps to identify the bacteria causing the infection which in turn will help to determine the best suited antibiotics that will kill the germs. This is very important as it helps in better management of serious patients. The yield of one blood culture is about 80% and in 20% of patients, no organism may grow even if there are bacteria circulating in the blood stream. By doing 2-3 blood cultures, the yield may increase to almost 100% and thus identification of bacteria increases.
What are the types of blood culture?
Blood can be incubated in regular broths and checked for growing colonies. They are cheaper but less reliable and can give negative results if the patient is already on antibiotics, Automated blood cultures are now available that are more reliable but are very expensive. Specialized automated cultures can give check for growth of bacteria even if the patient has received antibiotics.
Can cultures be done from other tissues?
Yes, any body fluid can be checked for growth of bacteria. However the yield differs for various fluids. Even pus and lymph nodes (glands) can be sent for culture.
Last updated on 24th December 2009