The choice of which blood culture medium to use in detecting
possible sepsis in trauma and emergency patients can make a difference in time
to bacterial detection and recovery, according to an article published in the
March 15 issue of Clinical Infectious Diseases.
Rebecca Zadroga, MD, from the Department of Infectious Disease,
University of Minnesota, and Hennepin County Medical Center, Minneapolis, and
colleagues conducted a head-to-head comparison of 2 widely used blood culture
media at a 462-bed acute care trauma center and emergency department between
February 1 and September 30, 2011.
They compared the Becton Dickenson Bactec Plus (Bactec) with the
bioMériux BacT/Alert FAN (BacT/Alert) in the collection of 9395 cultures. Of
those cultures, 831 were included in the analysis, 524 (33%) of which contained
pathogens. Exclusion criteria included pediatric patients and a difference in
the amount of bottles drawn.
The researchers found that Bactec yielded a 4.5-hour faster
bacterial detection time (P < .0001) than BacT/Alert and isolated
exclusively 182 (35%) of 582 pathogens (P < .001). They also found that
Bactec isolated 136 (39%) of 345 of the gram-positive cocci (P < .001), 48
(27%) of 175 gram-negative rods (P = .02), and 101 (52%) of 195 Staphylococcus
aureus (P < .001) and identified 59 (49%) of 120 septic events (P =
.004).
"If active antibiotics had been dosed 0–4 or 4–48 hours
prior to culture collection, the odds of that culture growing in BACTEC were
4.8- and 5.2-fold greater, respectively, than of growing in BacT/Alert (P <
.0001)," the researchers write. "Both were equivalent in the recovery
of yeast and when no antimicrobials were dosed."
Time is critical in the diagnosis of sepsis, the researchers
write, and guidelines recommend that antimicrobials be initiated within 1 hour
of sepsis recognition.
"The reality of this paradoxical relationship between rapid
treatment initiation and potential impact on diagnostics is exemplified in our
study, as 50% and 82% of patients seen in our wards and [intensive care unit]
environments, respectively, had a an antimicrobial administered [prior to
culture collection]," the researchers write.
Previous studies have not detected differences among blood
culture media in a hospital setting, and it is unclear why this study did show
differences, the researchers note. "[D]ifferences in the recovery and
[time to detection] for S. aureus is a key finding in our study that has
not been previously described," they write.
They
conclude, "[T]he diagnosis of sepsis remains both a clinical and laboratory
diagnosis."