Blood Cultures

Alias / keyword

Department

Infection Science (Microbiology)

Purpose

Culture for a range of bacterial and fungal pathogens

Sample type & Volume:  

Adult

Paired blood culture set (adults)

BacT/Alert FA PLUS aerobic

- Optimal 8-10ml.

This bottle recovers wide range of aerobic organisms and contains resin to neutralise antibiotics. Does not recover anaerobic organisms. (Green top)

BacT/ALERT FN PLUS Anaerobic

- Optimal 8-10ml. Recovers facultative and anaerobic organisms (Orange top)

If the volume of blood is inadequate for two bottles, the aerobic bottle should be inoculated first and then the rest inoculated to an anaerobic bottle.

Sample type & Volume:  Paediatric

BacT/ALERT PF PLUS Paediatric

Paediatrics/neonates up to 4ml in paediatric blood culture bottle

May be used for adults if only a small volume of blood can be obtained. Does not reliably recover anaerobic organisms (Yellow Top)

Sample collection requirements

Sampling of blood should be performed according to Department of Health guidelines Taking Blood Cultures – A Summary of Best Practice.

If blood for other tests is to be taken at the same venepuncture, the blood cultures should be inoculated first to avoid contamination. It is preferable to take blood for culture separately.

If it is clinically indicated, multiple blood culture sets may be collected. If this is done the following guidelines should be followed if possible:

• Collect sets from different venepuncture sites

• Collect sets at a different times

False negatives may occur if inadequate blood culture volumes are submitted.

Do not overfill bottles as this does not improve recovery rate

Clinical information required on request form

Relevant clinical data and details of recent or current antimicrobial treatment should be provided:

NB PLEASE STATE IF THERE IS A HISTORY OF IV DRUG USE, CONTACT WITH SEWAGE, LIVESTOCK,  EXOTIC OR IMPORTED ANIMALS, RECENT OR PROLONGED FOREIGN TRAVEL. 

If infection with HACEK or other unusual organisms suspected, contact consultant microbiologist to discuss as prolonged incubation may be required

(HACEK organisms: Haemophilus species Aggregatibacter Cardiobacterium Eikenella Kingella)

Please refer to the infection prevention pages of the UHNM website

Special transport requirements

Transport to laboratory immediately and do not refrigerate. For each hour delay to loading on the blood culture analyser there is both a loss of viability of organisms and an incremental delay to obtaining a result. Any delays will cause the temperature of the blood culture to migrate to ambient, resulting in delays to obtaining a positive culture. In alignment with laboratory standards, NHS England and NHS Improvement recommends for blood culture sample bottles to be incubated in a blood culture analyser as soon as possible, ideally within a maximum of four hours.

Stability

Blood culture bottles are stable at ambient temperature until date of expiry. Do not store unused bottles where they will be exposed to extremes of temperature.

Turnaround time

Positive bottles with organisms seen in Gram film are telephoned to the ward by authorised laboratory staff and the report will be posted electronically. Outside normal working hours Gram stain results are posted electronically but may not be phoned if the isolate is unlikely to be significant.

When blood culture bottles are loaded onto the system,  a “Negative to Date” statement is released electronically.

Interim result negative result will be reported after 48 hours -this will remain unchanged until the blood culture is finally reported negative after 5 days OR the bottles become positive.

For neonatal unit only – interim negative results are reported at 36 hours. A final report is issued after 5 days

Reference range

Not applicable

Clinical decision limit

Decision to repeat blood cultures should based on clinical condition or if advised by Infection Science Team

Referred test

No

Accredited to ISO 15189

Yes

General information

Expired bottles should be returned to the laboratory for disposal.

Interpretive comments may be added to the report