Blood Cultures

Microbiology

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Summary

The BD BacTec Blood Culture system used allows automatic monitoring of blood cultures. All blood culture bottles are continuously monitored over a 5 day period and positive results are relayed to the appropriate requester as soon as identified.

Usage

Culture test to look for the presence of Bacteria (and fungi) in blood.

Click here for – Mycobacteria Blood Culture

Specimen

Blood taken either from a peripheral vein or from a line (please specify on request.)

Specimen Container

BacTec Blood culture bottles (see picture):

• • Adult Set (2 bottles): 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 Set (1 bottle): Single BD BacTec Peds Plus/F bottle with a pink cap containing 40ml of clear colourless broth and latex beads.

Requesting

• Ensure time, date & appropriate clinical information is entered in the request:
  • Recent Travel History
  • If the patient has gastroenteritis
  • If the patient has endocarditis
  • Details of antibiotics

To Request On EPIC

For electronic requesting using EPIC (RDUH ONLY):

Search for: ‘Blood culture‘ or test code ‘LAB462‘

• Ensure that the barcode on the Blood culture bottles is not covered by specimen labels – this barcode is required to process the sample

Sample Collection

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

• • Clean procedure tray
  • Blood culture bottle(s) – see above, (Prior to use, inspect all vials and discard any vials showing evidence of contamination, damage or deterioration. Check expiry date.)
  • Sharps bin
  • 2% chlorhexidine in 70% alcohol for cleaning of venepuncture site and blood culture bottle tops
  • Vacutainer butterfly collection set with monovette adaptor (23g green, 21g blue wings)
  • Clean, non-sterile gloves
  • Disposable or non latex tourniquet
  • Alcohol hand rub

Preparation of bottles

• • Inspect all bottles and discard any showing evidence of contamination, damage or deterioration.
  • Check expiry date.
  • Remove the flip off plastic cap and clean the rubber septum of the culture bottles with chlorhexidine/alcohol swab and allow to dry for 30 seconds.

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)

1. 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. 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.

For an adult set:

• • • Attach aerobic (blue topped) bottle first. Collect 8-10mls.
    • Attach anaerobic bottle (purple topped). Collect 8- 10mls.

For a Paediatric Bottle:

• • • Inoculate 1-3 ml of blood into the 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.

1. 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.

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.

Sample collection – Needle and syringe method

1. 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. 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.

DO NOT change the needle between sample collection & inoculation. 

For an Adult Set:

• • • Inoculate aerobic (blue topped) bottle first with 8-10mls.
    • Inoculate anaerobic bottle (purple topped) with 8- 10mls.

For a Paediatric Bottle:

• • • Inoculate 1-3 ml of blood into the bottle.

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

It is essential that bottles are not overfilled; use the 5 ml graduation marks on the side of the vial to monitor the volume inoculated.

Post Collection

• • 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:
    • From within the hospital:
      • Ensure the collection has been completed on EPIC
    • From outside the hospital:
      • Ensure that the request form is completed fully

Sending Samples to Lab

Send to the laboratory in a plastic specimen bag as soon as possible – NICE guidelines recommends 4 hours from venipuncture to incubation within the laboratory.

Please Note – Samples MUST NOT be refrigerated.

Between 08:00-22:00:

• • The bottles should be transported to the Microbiology laboratory (Old Path Lab) as soon as possible, either by Porters or via the pneumatic tube system (POD) – 2900.

Between 22:00 – 08:00:

• • Send to Blood Sciences (A2) either by the Porters or via the pneumatic tube system (POD) to station 2912 – Samples will be loaded onto a satellite blood culture analyser within Blood Sciences.

Special Instructions

Please DO NOT overfill bottles.

Availability

Processed locally at RD&E

Turnaround Time

Up to 5 days for a negative result

Reporting

Preliminary negative results available at 48hrs for adult and 36hrs for paediatric blood culture sets, but bottles will continue to be monitored until 5 days have passed.

Urgent Specimen Instructions

All blood cultures should be transported to the laboratory as soon as possible.

Useful Links

For patients:

Blood Cultures – Lab Tests Online

For Healthcare professionals:

Improving The Blood Culture Pathway – Executive Summary – NHS England

UK SMI S 12: sepsis and systemic or disseminated infections – UKHSA

Specimen Labelling Procedure