Collection of Blood Cultures

Blood Culture Collection poster may be accessed here.

Sample Containers:

• Adult (Standard Set): One BD Bactec Plus Aerobic/F (grey cap) bottle containing 40ml of clear colourless broth and latex beads + One BD Bactec Lytic/10 Anaerobic/F bottle (purple cap) containing 40ml of clear yellow broth.
• Paediatric (Paediatric bottle): Single BD Bactec Peds Plus/F bottle with a pink cap containing 40ml of clear colourless broth and latex beads.
• Blood Culture for TB: One BD Bactec bottle – White capped bottle with narrow neck containing 40ml of clear broth. Contact laboratory for issue.

The Bactec system used at North Devon District Hospital allows automatic monitoring of the blood cultures. All blood culture bottles are continuously monitored over a 5 day period (7 days for those with clinical details of infective endocarditis) and positive results are relayed to the appropriate requester as soon as identified. An interim negative report is sent after 32 hours incubation, but bottles will continue to be monitored until 5 days have passed.

Number and Timing of Samples

Only take blood for culture when there is a clinical need to do so and not as routine

• Generally, two sets of blood cultures are preferred. This increases detection of pathogens and helps distinguish contaminants.
• If infective endocarditis is considered, please send a TOTAL of 3 sets of blood cultures initially and discuss with a Consultant Medical Microbiologist. These should be taken via different venepuncture sites.
• The timing of blood cultures does not need to coincide with spikes in temperature as the likelihood of a positive blood culture is not related to peaks of fever.

Previous antimicrobial therapy

• Ideally, blood cultures should be taken prior to antimicrobial treatment. When a patient is already receiving antimicrobials, blood cultures should be taken immediately before the next dose, with the exception of paediatric patients.

Blood volume

• Blood culture volume is the most significant factor affecting the detection of organisms in bloodstream infection.  False negatives may occur if inadequate blood culture volumes are submitted.
• The adult blood culture set consists of two bottles, one with a grey flip-off cap and label and the other with a purple flip-off cap and label. Optimum blood draw is 8-10ml in each bottle.
• A paediatric bottle with pink flip-off cap and label is available with an optimum blood draw of 1-3 ml. If only a small amount of blood can be obtained, such as in those with difficult venous access, it would be appropriate to use a paediatric bottle.

Kit preparation

• Prior to use, each vial should be checked for damage and evidence of contamination such as cloudiness, leakage, bulging or indented septum. DO NOT USE any vial showing signs of damage or contamination.
• Label bottles with surname, forename, date of birth and NHS or hospital number in space on bottles provided.
• If using printed labels, ensure they do not cover the removable bottle barcodes; please do not remove bottle barcode labels.
• For ease of volume control, mark the fill level on the side of the bottle prior to blood collection.
• Remove flip-off caps from bottles and swab the tops with a 2% chlorhexidine in 70% isopropyl alcohol swab (if not available, use alcohol swab – iodine is not recommended) and allow to dry.

Skin preparation

• Wash your hands with soap & water or use alcohol hand rub.
• Clean any visibly soiled skin on the patient with soap & water and then dry.
• Apply a tourniquet and palpate to identify vein.
• Clean skin with a 2% chlorhexidine in 70% isopropyl alcohol impregnated swab (if not available, use an alcohol swab) and allow to dry.

If a culture is being collected from a central venous catheter, disinfect the access port with a 2% chlorhexidine in 70% isopropyl alcohol impregnated swab and allow to dry (if not available, use alcohol swab).

Sample collection – winged blood collection (preferred method)

It is IMPORTANT to use the correct kit if this method is used  i.e. a BD Vacutainer^® Push Button Blood Collection Set with Pre-Attached Holder.

It is IMPORTANT that the bottle being inoculated is held at a position below the patient’s arm with the bottle in an upright position (stopper uppermost). This will prevent any potential back flow of media from the blood culture bottle. Monitor the draw process closely at all times during collection to assure proper flow is obtained and to avoid flow of the bottle contents into the adapter tubing.

Due to the presence of chemical additives in the culture bottle, it is important to prevent possible back flow and subsequent adverse reactions.

1. Wash and dry your hands again or use alcohol hand rub and apply clean examination gloves (sterile gloves are not necessary).
2. Attach winged blood collection set to blood collection adapter cap.
3. Insert needle into prepared site. Do not palpate again after cleaning.
4. 4. If blood is being collected for other tests, always collect the blood culture first.
5. Place adapter cap over the vial and pierce the septum. Hold the bottle upright and use the 5 ml graduation marks on the side of the vial to monitor the volume collected.

Adult Set: Starting with the blue capped (aerobic) bottle, inoculate  8-10 ml of blood into each bottle. It is essential that bottles are not overfilled; use the 5 ml graduation marks on the side of the vial to monitor the volume collected.

Paediatric Bottle: Inoculate 1-3 ml of blood into the bottle.

6. 6. When the desired volume has been drawn, other blood samples can then be collected as required.
7. Remove the tubing set from the vial.
8. After collection and while the needle is still in the vein, place gauze pad or cotton ball on the venepuncture site allowing it to cover the front barrel of the winged push-button device. Grasp the body of the device with the thumb and middle finger and activate the push button with the tip of the index finger to withdraw the needle from the patient.
9. To ensure complete and immediate retraction of device, make sure to keep fingers and hands away from the end of the blood collection set during retraction. Do not impede retraction. Make sure that the needle is fully retracted and is in the shielded position.
10. Apply pressure to the venepuncture site.
11. Cover the puncture site with an appropriate dressing.
12. Discard winged blood collection set in a sharps container.
13. Wash hands after removing gloves.

Sample collection – Needle and syringe method

1. Wash & dry your hands again or use alcohol hand rub and apply clean examination gloves (sterile gloves are not necessary).
2. Insert needle. Do not palpate again after cleaning.
3. 3. Collect 16 – 20 ml of blood (1-3 ml for paediatric bottle) and release tourniquet.
4. Cover the puncture site with an appropriate dressing.
5. If blood is being collected for other tests, always inoculate the blood cultures first.

Adult Set: Inoculate 8-10 ml of blood into each bottle starting with the purple capped bottle (anaerobic): do not change the needle between sample collection & inoculation. It is essential that bottles are not overfilled; use the 5 ml graduation marks on the side of the vial to monitor the volume collected.

Paediatric Bottle: Inoculate 1-3 ml of blood into the bottle.

6. Discard needle and syringe in a sharps container.
7. Wash hands after removing gloves.

Record procedure and send samples to laboratory

• Record the procedure with indication for culture, time, site of venepuncture and any complications in the patient’s record.
• Ensure the bottles are correctly labelled and that the specimen form is completed fully, including the name and designation of the person who took the sample printed on the form.
• Send to the laboratory in a plastic specimen bag as soon as possible. (Samples received out of hours are loaded onto a satellite blood culture analyser within Pathology Specimen Reception by Laboratory on-call staff).
• Please note – Samples must not be refrigerated.