In vitro activity of micafungin combined with amphotericin B or fluconazole against Candida parapsilosis
Abstract number: P2168
Marcos-Arias C., Eraso E., Carrillo-Muñoz A.J., Pontón J., Quindós G.
Objective: The aim of this study was to evaluate the in vitro activities of the combinations micafungin (MFG, Astellas, Japan) + amphotericin B (AMB, Sigma, USA) and MFG + fluconazole (FLC, Pfizer, Spain), against 30 blood isolates of Candida parapsilosis.
Methods: The minimum inhibitory concentrations (MIC) were determined according to Clinical and Laboratory Standards Institute guidelines for yeasts, and defined as the lowest drug concentrations that produced a 50% inhibition of visible fungal growth after 24 h of incubation. Drug interactions were assessed by the checkerboard microdilution method. Antifungal agents were placed in rows or columns of trays with MFG concentrations ranging from 0.06 mg/mL to 32 mg/mL, AMB concentrations ranging from 0.06 mg/mL to 4 mg/mL, and FLC concentrations ranging from 0.03 mg/mL to 2 mg/mL. The fractional inhibitory concentration index (FICI) was used to classify drug interaction as follows: FICI 0.5, synergistic; 0.5 < FICI 4, indifferent; and FICI > 4, antagonistic. Candida krusei ATCC 6258 and C. parapsilosis ATCC 22019 were used as quality control strains.
Results: Overall, MFG MICs ranged from 2 mg/mL to 16 mg/mL. The MICs at which 50% and 90% of all the isolates tested were inhibited (MIC50 and MIC90, respectively) were 8 mg/mL and 16 mg/mL and the MIC geometric mean (GM) 7.64 mg/mL. AMB MICs ranged from 0.25 mg/mL to 1 mg/mL. The MIC50 and MIC90 were 0.25 mg/mL and 1 mg/mL, respectively, and the GM, 0.40 mg/mL. FLC MICs ranged from 0.25 mg/mL to 1 mg/mL. The MIC50 and MIC90 were 0.5 mg/mL and 5 mg/mL, respectively, and the GM, 0.41 mg/mL.
The highest percentage of synergy was obtained combining MFG + AMB (22.2%) and the lowest combining MFG + FLC (6.7%). The remaining combinatory results were indifferent.
Conclusion: The highest number of synergistic interactions against C. parapsilosis was found for the combination MFG + AMB but only against 22.2% of isolates.
Funding: Projects PI061895 from Fondo de Investigación Sanitaria (Ministerio de Sanidad y Consumo of Spain) and IT-22207 from Departamento de Educación, Universidades e Investigación (Gobierno Vasco).
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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