In vitro evaluation of three bacterial culture systems for the recovery of Escherichia coli from equine blood.
OBJECTIVE
To evaluate the effectiveness of a commercial conventional blood culture system (BCS), a commercial resin-containing BCS, and a commercial lysis-centrifugation-based BCS for the recovery of Escherichia coli from equine blood samples inoculated with that organism.


METHODS
Samples of blood obtained from a clinically normal horse that were inoculated with E coli.


METHODS
Blood samples were aseptically collected and inoculated with an E coli specimen (50 CFUs/mL) that had been previously isolated from a foal with sepsis. Subsequently, samples were spiked with gentamicin at a concentration of 30 mug/mL, and 10 mL of each mixture was inoculated into 1 bottle or tube of each BCS. Samples were processed and incubated according to the manufacturer's guidelines and inoculated onto 5% sheep blood agar plates. Plated samples were examined macroscopically at regular intervals for as long as 72 hours. Detection of E coli and time to detection were recorded for each medium.


RESULTS
Detection frequency of E coli was significantly greater by use of the resin-containing BCS (14/23 bottles) than that achieved by use of the conventional BCS (7/23 bottles) or the lysis-centrifugation-based BCS (0/10 tubes). Mean detection time (6 hours after plating) did not differ between the BCS with conventional medium and the BCS with resincontaining medium.


CONCLUSIONS
Results suggest that a BCS with resin-containing medium may provide clinical benefit in the successful recovery of E coli from the blood of foals with sepsis that have been previously administered gentamicin.
Lorenzo-Figueras
Mireia
M
Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Pusterla
Nicola
N
Byrne
Barbara A
BA
Samitz
Eileen M
EM
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001431:Bacteriological Techniques / Q000592:standards / Q000662:veterinary*; D001769:Blood / Q000382:microbiology*; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000175:diagnosis / Q000382:microbiology / Q000662:veterinary*; D005260:Female; D005839:Gentamicins / Q000494:pharmacology; D006734:Horse Diseases / Q000175:diagnosis* / Q000382:microbiology; D006736:Horses
D000900:Anti-Bacterial Agents; D003470:Culture Media; D005839:Gentamicins