Blood culture is an important diagnostic investigation in some patients with serious and potentially life-threatening septic diseases (e.g. septicaemia, septic endocarditis, kidney infections, discospondylitis, etc.). Here are some advices from our expert dr. Marta Medardo, Head of Microbiology, on the correct procedure to use.

When should a blood culture be taken?

In all cases of suspected septicaemia, bacterial endocarditis or bacterial meningitis, fever of unknown origin, polyarthritis, discospondylitis, pneumonia, pleurisy and peritonitis.

How to perform a blood culture ?

At least TWO blood samples should be taken at a time interval (minutes to an hour apart in the case of acute/hyperacute symptoms; several hours apart, up to 12 hours, in the case of chronic symptoms) strictly BEFORE any antibiotic treatment (at least two samples are necessary because blood must be taken when the bacteria are actively replicating; a single sample may not show bacterial replication and could give false negative result).

Blood collection should be performed by shaving and surgically disinfecting the venous access. Each blood sample should be at least 2.5-5 ml of blood for feline sample and 5-10 ml of blood for canine sample (to be judged according to the weight and size of the animal; smaller volumes are also acceptable in paediatric patients or those with compromised volaemia).

Each blood sample should be placed in a blood culture bottle, which will then be correctly identified with the patient’s name and time of collection. Always remember to change needle and use a new one for inoculation.

To avoid possible contamination, it is good practice to place cotton wool soaked in alcohol on the plastic cap of the bottle

Which sampling is preferable?

Peripheral venous access (they are less contaminated according to the main guidelines)

How to send samples?

Samples should be sent as soon as possible (maximum 72h) and kept at room temperature.

Aerobic, anaerobic and fungi/yeasts are always performed on the complete blood culture.

Blood culture bottles available in our store:

BACT/ALERT® Biomerieux Blood Culture Bottles:

 ‘SA Plus Aerobic Bottles’ are suitable for aerobic microrganisms and yeasts in blood and other normally sterile body fluids (e.g. cephalorachid fluid, synovial fluid, effusions).

‘SN Plus Anaerobic Bottles are suitable for anaerobic microrganisms in blood and other normally sterile body fluids (e.g. cerebrospinal fluid, synovial fluid, effusions).

 Both media contain the new antibiotic-neutralising APB molecules, which are useful in reducing the inhibitory effect of any ongoing therapy on the growth of microrganisms in vitro.

 Inoculate a maximum of 10mL (follow the fill line on the bottle).

Oxoid blood culture bottles:

suitable for culturing aerobic, anaerobic and fungal microorganisms. Inoculate the sample up to a maximum of 10mL per bottle. As the bottle is made of glass, we recommend careful packaging during shipment.

 

 Dr. Marta Medardo

DVM, diplomate ECVM, EBVS® European Specialist in Veterinary Microbiology,

MyLav Expert in Microbiology