F1-2040. MIC Testing of Helicobacter pylori Using Etest Finafloxacin and the Reference Agar Dilution Method
Session: Poster Session: New Topoisomerase Inhibitors
Monday, October 27, 2008: 12:00 AM
Room: Hall C
Background: Finafloxacin (FIN) is a novel 8-cyano fluoroquinolone (FQ) that exhibits optimal activity at slightly acidic pH (5-6) where other FQs lose activity. FIN is intended for therapy of bacterial infections associated with an acidic environment such as H. pylori (HP) eradication and UTI. Susceptibility testing of HP, a fastidious slow growing organism, is challenging. The Etest stable gradient method has been evaluated for HP testing and is recommended by the European HP Study Group. This study compared MIC testing of FIN with Etest and agar dilution (AD) at neutral pH using a collection of HP, including FQ resistant strains. Methods: AD was done according to the CLSI method. For Etest, HP inoculum prepared in Mueller Hinton broth + 5% sera (3 Mc Farland) was streaked onto Mueller Hinton agar plates with 10% aged blood. Plates with Etest strips were then incubated under microaerophilic conditions at 35oC and read after 3 and 5 days. One QC strain and 36 clinical isolates were tested in quintuplicate and triplicates respectively, with both MIC methods. Results: MIC ranges and agreement between Etest and AD
Incubation
(days)
Agreement %MIC µg/mL
± 1 dilution± 2 dilutionsFQ-susceptibleFQ-resistant
389.595.40.012-0.1252-32
584.295.40.016-0.252-32
ATCC 43504
MIC (µg/mL)
EtestAD
0.032-0.1250.064-0.25
Acceptable inter-method MIC agreement was seen after 3 and 5 days of incubation. Resistance that manifested as hazy growth in inhibition ellipses was easier to detect with Etest. Results from repeat testing with both MIC methods and the reference strain showed good reproducibility (agreement >95% ± 2 dilutions). Conclusions: Substantially equivalent results can be obtained for MIC testing of FIN with HP using Etest and the CLSI reference method. Etest with its wide concentration range and simplicity of use makes it a useful MIC tool for drug development purposes especially for the testing of newer agents targeted against H. pylori.
Anette Engelhardt1, Anne Yusof2, Carolina Johansson2, Karin Sjöström1, Phion Ho2 and  A. Engelhardt,
AB BIODISK Role(s): Employee., (1)AB BIODISK, Solna, Sweden, (2)AB BIODISK


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