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Evaluation of the Merlin MICRONAUT system for rapid direct susceptibility testing of Gram-positive cocci and Gram-negative bacilli from positive blood cultures

Abstract number: 1732_194

Pietzcker T., Wellinghausen N., Poppert S., Belak S., Fieser N., Bartel M., Essig A.

Objectives: Bloodstream infections are life-threatening conditions which require timely initiation of appropriate antimicrobial therapy. We evaluated the automated Merlin MICRONAUT system for rapid direct microtiter broth antimicrobial susceptibility testing (AST) of Gram-positive cocci and Gram-negative bacilli from positive BACTEC 9240 blood culture bottles in comparison to the standard method on the Merlin MICRONAUT system.

Methods: This prospective study was conducted under routine working conditions during a 9-month period. Altogether, 504 isolates and 11,819 organism–antibiotic combinations from 409 patients were evaluable for comparison of direct and standard AST on the Merlin MICRONAUT system.

Results: Concerning Gram-negative bacilli, direct and standard AST was evaluated in 110 isolates and MIC agreement was found in 98.1% of 2,637 organism–antibiotic combinations. Category (SIR) agreement was found in 99.0%, with 0.04% very major, 0.2% major, and 0.8% minor errors. Concerning Gram-positive cocci, 373 isolates were evaluated and MIC agreement was found in 95.6% of 8,951 organism–antibiotic combinations. SIR agreement was found in 98.8%, with 0.3% very major, 0.4% major, and 0.5% minor errors. In addition, for the first time direct and standard AST were evaluated on 21 blood cultures positive with Streptococcus spp. MIC agreement and SIR agreement was found in 96.5% and 97.8%, with 1.7% very major, 0% major, and 0.4% minor errors.

Conclusion: Direct AST of Gram-negative bacilli and Gram-positive cocci from positive blood cultures on the MICRONAUT system is a reliable technique that allows omitting repeat testing of subcultured isolates. Thereby, it significantly shortens the time to result of blood culture testing and has a positive impact on patient care.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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