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Blood cultures

Blood culture process

This hospital uses the Biomerieux BacT/ALERT 3D colorimetric detection system for processing blood cultures. The carbon dioxide (CO2) produced by bacterial growth changes the colour of the colorimetric sensor at the base of each bottle and alerts the biomedical scientist to the presence of potential bacterial growth.



The system’s efficiency depends on the quality of the sample. Here are some tips to ensure a good quality test result

  • Fill aerobic bottle (blue) first

  • Collect the blood culture before any other blood tests are taken

  • Take the sample before antibiotics are administered where possible

  • DON’T over fill the bottle – this WILL lead to false positives

  • Don’t tear off any barcodes; these are needed in the laboratory

Procedure for taking a blood culture sample

1. Equipment preparation

  • Wash and dry your hands or use alcohol hand scrub

  • Gather all equipment: a blood culture pack, gloves, sharps bin, and place on a blue ANTT tray

  • Ensure that the barcodes on the blood culture bottle are not covered by additional labels and that any tear –off barcode labels are not removed.

  • Check the bottom of the blood culture bottle and do not use if there is a central yellow spot which indicates the bottle is contaminated

  • Remove plastic caps and clean the top of each bottle with a separate 2% chlorohexidine in 70% isopropyl alcohol impregnated wipe (Sani-cloths in the pack) and allow them to dry.

2. Patient preparation

  • Positively identify patients as per the Trust protocol and obtain verbal consent

  • Apply a disposable tourniquet (in the pack) and palpate to find a vein

  • Wash and dry hands or use alcohol hand rub and apply clean examination gloves (sterile gloves are not necessary)

  • Clean any visibly soiled skin on the patient with 2% chlorohexidine in 70% isopropyl alcohol using the non touch pad (Chloroprep Frepp in the pack) for 30-60 secs and allow to dry for 30-60secs

  • If a culture is being collected from a central venous catheter, disinfect the access port with a 2% chlorohexidine in 70% isopropyl alcohol impregnated wipe. Please note blood cultures must only be taken from CVCs if blood cannot be obtained from a peripheral vein or when a line related sepsis is suspected.

3. Sample collection

  • Remove winged blood culture set with collection adapter (in the pack) from its wrapping

  • Insert needle into prepared site. IMPORTANT: Do not palpate vein again after cleaning

  • Place adapter cap over blood culture bottle (in the pack) and pierce septum. IMPORTANT: Fill aerobic bottle first (blue top)

  • Hold bottle upright and use the bottle graduation lines to accurately gauge sample volume and collect 10mls into each sample bottle

  • If blood is being collected for other tests, always collect the blood culture samples first (see local vacutainer guides for sample order)

  • Release tourniquet and dispose

  • Remove the needle from the vein using the vein activator on the collection set

  • Cover the puncture site with an appropriate dressing

  • Discard winged blood collection set in a sharps container. Discard all other used consumables into a yellow clinical waste bag

  • Wash hands after removing gloves

  • Label the bottles

  • Record the procedure with indication for culture and any complications in the patient’s record. Also complete the audit sticker (in the pack) and place in patient record

Paediatric bottles

These bottles contain a larger volume of 30ml of clear liquid media which contain absorbent polymeric beads. This formulation is designed to enhance the performance of the culture only. Storage of pre-inoculated bottles remain the same: store at room temperature away from direct sunlight.  Inoculation procedures also remain the same: inoculate with 4ml of patient blood and transport to the microbiology without delay.

Last modified: 26/03/2015