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Bloodstream infections: fast diagnosis using molecular tools

Impact of the BIOFIRE® Blood Culture Identification (BCID) Panel compared to VITEK-MS and the VITEK-2 ID/AST instrument in the diagnosis and management of bloodstream infections in a 24-hour laboratory setting

April 18 • P0184

R. Davidson1, D. Haldane1, J. Leblanc1, I. Davis1, Z. Hussain1, G. Patriquin1, H. Alsidairi1, T. Hatchette1

1) Halifax, Nova Scotia Health Authority, Halifax, Canada

Background: The rapid identification and reporting of blood-borne isolates allows physicians to promptly manage their patients with the most appropriate antimicrobial therapy, aimed at improving patient outcomes. Technologies, such as the BIOFIRE® Blood Culture Identification (BCID) Panel, incorporate a multiplex PCR amplification and detection system allowing the identification of 24 pathogens and 3 antimicrobial resistance markers. We evaluated the BCID Panel in a 24-hour laboratory prospectively against the VITEK-MS® and retrospectively against the VITEK-2® ID/AST instrument.

Materials/methods: Blood cultures identified as positive (BD Bactec®) were plated onto appropriate media and gram stained. Bottles with visible bacteria on gram stain were processed using the BCID. Simultaneously, a direct, or, where necessary, re-processed identification after 6 hours of growth detection technique using the VITEK-MS® was performed. Technologists relayed the results to the wards in the first half of the study (268 patients), microbiologists discussed positive results with physicians in the second half of the study (265 patients).

Results: Five hundred thirty-three unique patients (blood cultures) were analyzed. Mean time to identification for the BCID was 1.39 hours. In comparison, mean identification times for the VITEK-MS® and VITEK-2® were 1.7-10.4 hours (direct and indirect) and 25.5 hours respectively. The BCID correctly identified 91% (485/533) of all isolates (8% of isolates not found in the BCID database). VITEK-MS® identified approximately 80% of gram negatives and 60% of gram positives by direct detection, the remaining isolates required a minimum of 6 hours growth prior to identification. Thirty three percent of all blood-borne Staphylococci were methicillin resistant. The one-hour identification and detection of mecA by BCID resulted in a statistically significant reduction in empiric vancomycin use during the study period. Compared to historic controls, physicians used less piperacillin-tazobactam and carbapenems empirically when results were discussed with a microbiologist. Twenty-eight percent of cultures were polymicrobial. The BCID correctly identified all isolates in 86% (24/28) of cases including one case with 8 pathogens.

Conclusions: The BCID is a rapid detection system that identified 91% of blood-borne pathogens an hour from detection. It is an effective tool in antimicrobial stewardship resulting in more appropriate managements of patients.

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