CaCi17 Retest at Dose Measured in Microorganism System Using Plate Reader - 2148-02_Inhibitor_Dose_CherryPick_Activity
Assay Overview: The basic assay strategy will consist of a highly fluconazole-resistant C. albicans clinical isolate cultured in microtiter plates. Test compounds that inhibit subsequent growth will merit further evaluation. This whole cell phenotypic screening approach will only capture compounds that retain activity in biological media and are capable of entering and accumulating in fungi to more ..
BioActive Compounds: 34
Keywords: Candida albicans, glycolysis, respiration
Assay Overview: The basic assay strategy will consist of a highly fluconazole-resistant C. albicans clinical isolate cultured in microtiter plates. Test compounds that inhibit subsequent growth will merit further evaluation. This whole cell phenotypic screening approach will only capture compounds that retain activity in biological media and are capable of entering and accumulating in fungi to bioactive concentrations. Grossly cytotoxic compounds will be removed through subsequent counterscreens. Compound activity will be measured by the metabolism of Alamar Blue, a cell stain that is metabolized to a fluorescent product by living cells but that remains non-fluorescent in wells with growth-inhibited organisms.
Expected Outcome: Reduction of signal due to cell death.
Amphotericin B 10 uM in well
Synthetic Defined Growth Medium
RPMI 1640 medium, (powder without sodium bicarbonate; Invitrogen 31800-089)
Uridine 8 mg/ml in water (Sigma)
Glucose 40% (w/v) in water (Sigma)
MOPS Buffer (Sigma)
Test Strain: C. albicans CaCi-17 (Redding et al., 1994, Clin Infect Dis 24:235-247)
Inoculate 500 ul of strain from cryopreserved stock into 250 ml shaker flask containing 30 ml growth medium. Shake at 30 degrees C overnight.
Read OD 600 of fungal culture using standard plate reader. Dilute to starting OD of the fungal inoculum of 0.00015 A600.
384 well black sterile Corning plates (PN 3712)
Add Pen/Strep at 0.1 ml per 10 ml media.
Using Combi, dispense 40 uL/well of fungal suspension into all wells.
Pin 100 nL from compound plates into assay plates.
Incubate plates in humidified (90 % humidity) incubator at 37 degrees C without agitation for 48 hrs.
Add 5 uL Alamar Blue (1:40 dilution in PBS) to each well. Incubate 2 hours. Read fluorescence on standard plate reader.
PRESENCE OF CONTROLS: Neutral control wells (NC; n=36) and positive control wells (PC; n=36) were included on every plate.
EXPECTED OUTCOME: Active compounds result in decreasing readout signal.
ACTIVE CONCENTRATION LIMIT:
For each sample, the highest valid tested concentration (Max_Concentration) was determined and the active concentration limit (AC_limit) was set to equal (2)(Max_Concentration).
The raw signals of the plate wells were normalized using the 'Neutral Controls Minus Inhibitors' method in Genedata Assay Analyzer (v7.0.3):
The median raw signal of the intraplate neutral control wells was set to a normalized activity value of 0.
The median raw signal of the intraplate positive control wells was set to a normalized activity value of -100.
Experimental wells values were scaled to this range.
PATTERN CORRECTION: No plate pattern correction algorithm from Genedata Condoseo (v.7.0.3) was applied.
MEASUREMENT USED TO DETERMINE ACTIVE CONCENTRATION (AC): AC50
AC values were calculated using the curve fitting strategies in Genedata Screener Condoseo (7.0.3).
AC values were calculated up to the active concentration limit described for each sample.
pAC was set to equal -1*log10(AC)
Activity_Outcome = 1 (inactive) when:
a) compound shows activity but in a direction opposite to the expected outcome
in these cases, values describing curve fitting parameters (Sinf, S0, Hill Slope, log_AC50, log_AC50_SE) are set to null
b) curve fit is constant where activity is > -30% and < 30% at all tested concentrations, or
c) AC > AC_limit
Activity_Outcome = 2 (active) when:
AC <= AC_limit
Activity_Outcome = 3 (inconclusive) when:
a) Curve fitting strategy resulted in a constant fit with activity >= -70% but <= -30%, or
b) The fit was deemed not valid due to poor fit quality.
If PUBCHEM_ACTIVITY_OUTCOME = 1 (inactive) or 3 (inconclusive),
then PUBCHEM_ACTIVITY_SCORE = 0
If PUBCHEM_ACTIVITY_OUTCOME = 2 (active)
then PUBCHEM_ACTIVITY_SCORE = (10)(pAC)
Scores relate to AC in this manner:
120 = 1 pM
90 = 1 nM
60 = 1 uM
30 = 1 mM
0 = 1 M
When the active concentration (AC) is calculated to be greater than the highest valid tested concentration (Max_Concentration), the PUBCHEM_ACTIVITY_SCORE is calculated using Max_Concentration as the basis.
When the active concentration (AC) is calculated to be less than the lowest tested concentration, the PUBCHEM_ACTIVITY_SCORE is calculated using the lowest tested concentration as the basis.
The individual dose data point columns ('Activity_at_xxuM') reported here represent the median of valid (unmasked) replicate observations at each concentration. These values are the inputs to a curve fitting algorithm.
All other data columns represent values which are derived during the curve fitting algorithm; this may sometimes include automatic further masking of some replicate data points.
Occasionally this results in perceived inconsistencies: for example, between the derived 'Maximal_Activity' and the apparent most active data point.
Categorized Comment - additional comments and annotations
* Activity Concentration. ** Test Concentration.
Data Table (Concise)