835. Clinical Comparison of Contemporary Aerobic Blood Culture Monitoring Systems for Isolation of Bacterial and Fungal Pathogens
Session: Oral Abstract Session: Advances in Diagnostics
Saturday, October 22, 2011: 9:30 AM
Room: 151AB
Background:  BACTEC Plus (Becton Dickinson)(BA) and BacT/Alert FAN (BioMérieux)(BT) are two established blood culturing systems which have not been clinically compared in over 15 years. This study is part of a 9 month hospital wide evaluation designed to compare bacterial recovery from blood cultures(BC) submitted to the microbiology laboratory using these two systems.

Methods: In a 469 bed level I trauma center, blood drawn from adults with suspected sepsis was inoculated into paired aerobic BA and BT media (blood inoculated into BA anaerobic media was collected but not studied). Fill volumes were recorded but 8-10 mL per bottle was desired. Bottles were incubated in their respective systems. Positive cultures were removed, Gram stained, subcultured, and results called to providers. Isolates were deemed clinically significant (CS) or contaminants based on IQLM guidelines or clinician consensus.

Results: 3,137 blood culture sets were drawn over an 11 week study period. There were 387 positive cultures and 284 were included in the study. Positive cultures in unpaired, pediatric, or anaerobic bottles were excluded. There were 187 CS isolates from 174 patients. 32 bacterial and 5 yeast/fungus species were recovered. BA recovered 235/284 (83%) of all isolates and 167/187(89%) of CS isolates. BT recovered 156/284 (55%) of all isolates and 102/187(55%) of CS isolates. BA picked up 65(35%)(p<0.001) more CS isolates than did BT. Time to detection (TTD) favored BA in 75/105(71%) isolates by an average of 4.7 hrs. Discordant growth affected 63 patients, of whom 38 had complete discordance (CD) defined by the inability of one culture system to recover all organisms for that patient. For CS isolates, CD favored the BA system in 27/38 (71%) patients and the BT system in 11/38 (29%) (p<0.001) patients. The other 25 patients had differences in the number of positive BC sets between the systems.

Conclusion: The BA system has higher recovery rates of CS isolates and faster TTD. On average, a patient with a blood stream infection was identified only by the BA system every 2.7 days. Rapid, effective recovery of CS blood stream isolates is essential for appropriate clinical care. Differences in BC recovery rates from different BC systems may influence antibiotic  and management decisions.

Subject Category: D. Diagnostic microbiology

Rebecca Zadroga, MD1, Richard Gottschall2, Vickie Nordberg2, David Williams, MD3 and Glen Hansen, PhD4, (1)University of Minnesota, Minneapolis, MN, (2)Microbiology, Hennepin County Medical Center, Minneapolis, MN, (3)Hennepin County Medical Center, Minneapolis, MN, (4)Microbiology , Hennepin County Medical Center, Minneapolis, MN


R. Zadroga, None

R. Gottschall, None

V. Nordberg, None

D. Williams, None

G. Hansen, None

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