ACS 200 Candida Albicans Kill Time Study

Antimicrobial Activity of Advanced Cellular Silver (ACS) 200

Using Candida albicans
Test Solution: ACS 200 Submitted April 29, 2009
August 10, 2009
Results RNA, LLC
Richard A. Robison, Ph.D.
Department of Microbiology
Brigham Young University


The purpose of this study was to determine the antimicrobial activity of ACS 200 on Candida albicans. This was accomplished by performing standard kill-time suspension tests using a 2 minute contact time.


A.   Test organism
The test suspension was prepared by growing a 24hr culture of Candida albicans in 5 ml of Sabaroud Dextrose broth at 37 °C. The suspension was then centrifuged, washed and re-suspended in 1ml sterile water.
B.    Neutralizers
The Neutralizer solution consisted of 9ml tubes of 10% Tween 80, 6.0% Tamol, 1.7% lecithin, 1% Tryptone, 0.6% Sodium Thiosulfate, and 1.0 % Cysteine.
C.    Kill-Time Procedure
1. 9.9 ml of the ACS 200 test solution was added to a 20×150 mm sterile bacterial culture tube. This tube was equilibrated in a 20 °C water bath. Then, 100 µl of the C albicans suspension was added at time zero.
3. After the specified contact time (2min), 1.0 ml of bacterial suspension and ACS 200 test solution was added to 9.0ml of neutralizer. The tube was mixed thoroughly.
4. After two min, the neutralized suspension was serially diluted 1:10, in physiological saline solution (PSS).
5. The number of viable organisms in selected dilution tubes was assayed by membrane filtration. One ml aliquots were plated in duplicate. The membranes were washed with about 100 ml of sterile PSS and removed to Sabaroud Dextrose Agar plates. The plates were incubated at 37 °C for 24 and 48 hours.
6. The number of colonies on each filter was counted and log reduction and percent kill values were computed.
D.   Controls
1. A titer of the test suspension was computed by performing membrane filtration assays on selected 1:10 dilutions in PSS of the test suspension.
2.A neutralizer control for the disinfectant was performed by adding 1.0 ml of ACS 200 test solution to 9 ml of neutralizer and then inoculating the mixture with 0.1 ml of the 1:1×105 dilution of the titer. This produced about 44 CFU / ml in the tube, which was allowed to stand for 20 minutes prior to dilution and assay by membrane filtration using duplicate 1 ml samples.
Candida albicans: Titer.

Number of colonies 1:1×107 1:1×108 1:1×109
39 6 0
50 4 0

Titer: 4.45 x 108cfu/ml
ACS 200: (Received 04/29/09)

Dilution of C. albicans/disinfectant suspension
Exposure Time
2 min
1:1×101 1:1×102 1:1×103 1:1×104
0 0 0 0
0 0 0 0


Neutralization Control Expected Counts:

Percent of Expected

Undiluted 1:10 Undiluted 1:10
ACS 200 54 3


39 3

Sterility controls

Material Counts
Neutralizer 0
Sterile Water 0
ACS 200 0
Columbia Agar 0

Results of the titer showed a viable C. albicans concentration of 4.45 x 108 organisms per ml in the original suspension. Inoculation of 9.9 ml of the test solution with 0.1 ml of this suspension produced an initial concentration of 4.45 x 106 C. albicansper ml in the assay tube.
Results from these procedures allowed log reduction (LR) and percent kill (PK) values to be calculated using the formulas: 1) LR = Log(S/S0); where S = concentration of viable organisms after the specified contact time; and S0 = the initial concentration of viable organisms at time zero. 2) PK = (1 – (S/S0)) x 100. These values are shown below.

Test Solution Contact Time Log Reduction (LR) Percent Kill (PK)
ACS 200 2 min >5.95 >99.99989

Neutralization control data revealed that the neutralizer was able to adequately neutralize each solution. Observed count was 106% of those expected for the ACS 200 solution. Sterility controls showed no contamination issues.
Dates: August 7 – August 10, 2009
Performed By:
Emily Moore Research Associate
Supervised by:
Richard A. Robison, Ph.D.
851 WIDB
Brigham Young University
Provo,Utah 84602
Please Note: This report does not constitute endorsement by Richard A. Robison or Brigham Young University, of the tested products in any way. The names ‘Richard A. Robison’ and/or ‘Brigham Young University’ may not be used in any type of promotional published material, either written or electronic, without express written permission from both parties.