Amphotericin B susceptibility testing of Candida species by flow cytometry

✍ Scribed by Maurice R. G. O'Gorman; Roy L. Hopfer

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 455 KB
• Volume: 12
• Category: Article
• ISSN: 0196-4763
• DOI: 10.1002/cyto.990120808

✦ Synopsis

We have developed an 8 hr flow cytometry (FCM) method for assessing susceptibility of yeasts to amphotericin B (AmpB). The method detects both highlevel and relative-resistance to the drug. Variables found to affect fluorescence of control and AmpB treated cells included pH, presence of glucose, incubation conditions, concentration and length of exposure to both AmpB and ethidium bromide (ETBR), and the degree of resistance to AmpB. The FCM method was op- timized based on increased red fluorescence intensity (RF), decreased forward angle light scatter (FALS), and a negative gating technique. A dose response was seen between 0.1 and 10 pg AmpB/ml for the susceptible control strain. Greater than 50% of cells from all susceptible strains tested transfer into the negative gate when exposed to 2.5 pg Amp B/ml while fewer than 5% of cells of the highly resistant C. tropicalis (ATCC 28707) are affected at concentrations up to 20 pg/ml. This method may provide a more accurate assessment of Amp B susceptibility than conventional tube dilution methods.