Blood Culture
Special Instructions (if applicable):
For good laboratory test results you must have proper collection and handling of the specimen. It is best to collect blood cultures when the animal has an elevated temperature, prior to placing it on antibiotics or after it has been off antibiotics for at least two to three days. In the latter instance, if sulfonamide drugs or penicillin was the antibiotic used for treatment, please use culture broth which has an antibiotic inhibitor present. Please state clinical diagnosis and time of collection. List current antibiotic therapy, clinical diagnosis and any special organisms suspected to be present or to be ruled out. Indicate if culture is for BrucelIa or Francisella testing. Do not use expired blood culture media.
Collection
- Properly label one aerobic and one anaerobic
- 1-3 ml of blood should be drawn prior to initiation of antimicrobial therapy and placed in pediatric bottles. If more than one culture is ordered, the specimens should be drawn separately no less than 30 minutes apart. This is to rule out the possibility of transient bacteremia.
- An animal in the advanced stages of disease is most desirable.
- Specimens should be collected from more than one diseased animal.
- Specimens should be collected from animals in various stages of illness.
- It is desirable to have duplicate samples from one animal, but this may not be practical, especially in small laboratory animals.
- Strict aseptic technique is essential. If present, remove the plastic cap from the blood culture bottles, swab the stoppers with tincture of iodine or Povidone iodine and allow stoppers to dry.
- For any laboratory animal, blood may be collected via cardiac stick if the animal is first anesthetized. This technique also provides a large sample.
Pre-incubate or maintain specimen at room temperature. Do not refrigerate.
Arrangements for Specimen Transport
Specimens should be sent to MDS/RRDA as soon as possible so that contact time with atmospheric oxygen is minimized. Advance arrangements with MDS/RRDA are always appreciated so that rapid transport of specimens can be arranged and the specimens processed immediately on arrival. If you call MDS/RRDA (858-450-9990) prior to sample collection, our courier service can pick up and deliver the samples to the laboratory within an hour.
Preparation
The major difficulty in interpretation of blood cultures is potential contamination by skin flora. This difficulty can be markedly reduced by careful attention to the details of skin preparation and antisepsis prior to collection of the specimen.
Skin Preparation
- First shave the skin, cleanse the venipuncture site with isopropanol.
- Then use tincture of iodine or Povidone iodine to disinfect the site using progressively larger concentric circles. Iodine should remain in contact with skin for about 1 minute or until dry to ensure disinfection.
- The venipuncture site must not be palpated after preparation.
- Blood is then drawn. Following venipuncture, alcohol is used to remove the iodine from the site.
- Cleanse the bottle with disinfectant
- Remove cover caps from bottles (1 aerobic MH07591 and 1 anaerobic MH07592) and cleanse each rubber septum with separate 70% alcohol swabs. Allow septum to dry for 1 mm before inoculating.
- Virtually any organism, including normal flora, can cause bacteremia.
- A negative culture result does not necessarily rule out bacteremia; false-negative results occur when pathogens fail to grow.
- A positive culture result does not necessarily indicate bacteremia; false-positive results occur when contaminants grow.
- Gram-negative bacilli, anaerobes and fungi should be considered pathogens until proven otherwise.