In vitro evaluation of three bacterial culture systems for the recovery of Escherichia coli from equine blood.

The research article details an investigation into the efficacy of three different bacterial culture systems in recovering Escherichia coli from equine blood. The results suggest that a system containing a resin medium may offer greater success in the recovery process.

Research Methods

In the process of evaluating the effectiveness of three different commercial bacterial culture systems (BCS), samples of equine blood were taken and then inoculated with E. coli. This bacterium was taken from a specimen previously isolated from a foal with sepsis. The methods included:

• Collection of blood samples from a clinically normal horse
• Inoculation of these blood samples with an E. coli specimen at a concentration of 50 CFUs/mL
• Spiking samples with gentamicin, an antibacterial medication, at a concentration of 30 μg/mL
• Inoculation of 10 mL of each of these mixtures into separate bottles or tubes corresponding to the three different BCS

Each sample was processed and incubated following the manufacturer’s guidelines. Subsequent steps included inoculation onto 5% sheep blood agar plates and close examination of the plated samples at regular intervals for up to 72 hours.

Results and Findings

The detection of E. coli and the time taken to achieve this was recorded for each bacterial culture system. The findings were as follows:

• The BSC containing resin showed the highest frequency of E. coli detection, with successful recovery in 14 out of 23 bottles
• The conventional BCS ranked next, with detection in 7 out of 23 bottles
• The lysis-centrifugation-based BCS unfortunately failed to detect E. coli in any of the 10 tubes tested
• The mean detection time (approximately 6 hours after plating) remained consistent across the two successful systems – the conventional and the resin-containing one

Conclusions

The study concludes that a BCS containing a resin medium might deliver better results when it comes to successfully recovering E. coli from equine blood, especially in cases of foals with sepsis that have previously been treated with gentamicin.