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Microbiology cultures — blood cultures
Category: Biopsies, Lab & Pathology Tests · All biopsies, lab & pathology tests
What it is
Blood cultures detect bacteria or fungi living in the bloodstream. Blood is drawn into special bottles (usually two sets from different sites) and incubated in machines that flag growth, after which organisms are identified and tested for antibiotic sensitivities.
Why it is done
They are taken when serious infection or sepsis is suspected — high fever, rigors, low blood pressure — ideally before antibiotics (without delaying them), and to investigate fevers of unknown origin and infections of heart valves (endocarditis).
How to prepare
No fasting is needed. Meticulous skin cleaning is essential to avoid contaminating the sample with skin bacteria — tell the team if you have allergies to antiseptics. If you already have a central line, samples may be taken both from the line and a vein to help locate the infection source.
What happens during the procedure
Using sterile technique, blood is drawn into aerobic and anaerobic bottles in a set order and volume (adequate volume is the biggest factor in detection). The bottles go straight to the laboratory incubator system.
Afterwards — recovery & results
Preliminary results appear when growth is detected — often within 24 to 48 hours — with full identification and sensitivities over the following days. A positive result prompts urgent clinical review and usually intravenous antibiotics targeted to the organism.
Risks & considerations
Bruising from the draw is the only direct risk. False positives from contamination can lead to unnecessary antibiotics — the careful technique, and taking two sets, minimises this.
Watch: Microbiology cultures — blood cultures videos
Real procedure videos from the MedicalVideos.com library. Some clinical footage is graphic — that is the nature of a medical video library.
Related guides on MedicalVideos.com
Frequently asked questions
Why two sets from different places?
It increases detection and interpretation: the same skin organism in only one bottle is usually contamination, while the same true pathogen in both confirms bloodstream infection.
My culture grew something but I feel better — still treated?
Usually yes if it is a genuine pathogen — bloodstream infection can seed heart valves, joints and devices. Your team weighs the organism and your course carefully.
Related procedures — Biopsies, Lab & Pathology Tests
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