Standardization of inoculum preparation for antifungal susceptibility testing of emerging filamentous fungi

E.Petrikkou, A.Gomez-Lopez, A.Aberkane, M.Cuenca-Estrella, J.Mosquera, I.Georgopoulos, J.L.Rodrí­guez-Tudela


Background: NCCLS document M38-P suggests inoculum preparation by spectrophotometric procedure. Colour and size of spores which are species dependent influence the OD values. Alternatives as spore enumeration could be more appropriate. Methods: A total of 156 isolates belonging to 8 different species were tested. Inocula suspensions were prepared in sterile distilled water or Tween 20 (0.1%) for Aspergillus inocula (previous unpublished studies indicated that higher concentration of Tween 20 effects antifungal MICs). Inocula were adjusted between 1 and 5x 106 CFU/mL by spore enumeration with Neubauer improved chamber (NB) and quantified by plating aliquots onto Sabouraud (colony-counting: CC). OD of the inoculum was measured at 530 nm (SP). Data were transformed to logarithmic values and statistical analysis was performed. Conclusions: (1) The range of OD units obtained was very broad for all species analysed. Thus, spectrophotometric methodology cannot be recommended as an appropriate procedure for inoculum preparation of filamentous fungi. In addition all r-values were

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Full conference title: 

11th European Congress of Clinical Microbiology and Infectious Diseases
    • ECCMID 11th (2001)