Re: Double Blind Bind

William_at_Occam.com
Date: 06/12/04 

Date: Sat, 12 Jun 2004 08:43:07 -0400

Have you read the articles that I posted recently?

Here's some of the text from J. Wound Care. (2004) 13:154-155. Note
the use of ASAP.

Three samples of colloidal silver were tested:
. One sample which is available commercially on
the internet
. Two samples which were prepared in our laboratory
using standard chemical methods, whereby a
silver nitrate solution was reduced with either
tannic acid or sodium citrate.

The commercially available sample was the ASAP
Sporicidal Strength solution (lot: 030337, expiry
date: February 2005), labelled as containing 22ppm
silver in purified water. The particle size is about
10nm (manufacturer’s specification). This was provided
for research purposes by American Biotech
Labs (Alpine, Utah, USA).

The reduction with tannic acid was carried out
using the procedure described by James.14 To 500ml
of doubly distilled water, 20ml of 0.1M silver nitrate
solution and 5ml of 0.1% tannic acid solution were
added. The mixture was heated to 70–80°C, and
10ml of 1% sodium carbonate solution was added
to portions that were continually stirred, yielding a
clear, tea-coloured, colloidal silver solution.
The third sample was prepared according to the
method described by Bell and Myrick.15 500ml of
3.83 x 10-3 M silver nitrate solution in doubly distilled
water was heated to boiling point, and 3ml of
0.442M sodium citrate was added to it drop by drop
over one hour, during which time the solution was
stirred vigorously, producing a cloudy, greyish colloidal
solution. This was then boiled for one hour,
cooled and its volume made up to 500ml with distilled
water.

Transmission electron microscopy was used to
determine the size of the silver particles. The solution
prepared with tannic acid had particles of
10–30nm in size, while those in the solution prepared
with sodium citrate were 20–50nm.
The 22ppm, 403ppm (with tannic acid) and
413ppm (with sodium citrate) colloidal silver solutions
were tested using the agar-well diffusion assay.
Ciprofloxacin 0.3% eye/ear solution (Deepak Enterprises,
New Delhi, India) was used as the control
agent. The test organisms were:
. Staphylococcus aureus NCTC-08532
. Pseudomonas aeruginosa NCIMB-8626
. Escherichia coli NCIMB-8545
. Proteus mirabilis NCTC-11938
. Bacillus cereus NCTC-02599
. Aspergillus niger (our own isolate).
Mueller-Hinton agar CM337 (Oxoid, Basingstoke,
UK) was used to culture the organisms. Microorganisms
(Staphylococcus aureus, Pseudomonas aeruginosa,
Escherichia coli and Proteus mirabilis) cultured from
the ears of consenting patients with chronic suppurative
otitis media were also included in the test.
The plates were seeded with the test organisms,
and 150µl of each test agent was transferred into
the wells. In addition, an agar-disk diffusion assay
was performed with a standard set of antibiotics in
Mastring-S M41disks (Mast Diagnostics, Mast Laboratories,
UK). After 24 hours of incubation, zones
of inhibition on the plates were measured.
In another test series, the standard test procedure
of the Association of Official Analytical Chemistry
was used to compare the phenol coefficient against
colloidal silver and two disinfectants:
. Savlon (Novartis)
. Ethanol (absolute, 99%).
Phenol coefficient is a numerical value that compares
the bactericidal concentration of a disinfectant
with that of phenol. This value is obtained by dividing
the greatest dilution of disinfectant capable of
killing bacteria in 10 minutes by the greatest dilution
of phenol showing the same results.

Test bacteria were Pseudomonas aeruginosa
NCIMB-8626 and Staphylococcus aureus NCTC-
08532. Bacterial growth was monitored in nutrient
broth CM1 (Oxoid, Basingstoke, UK) by visual
inspection of turbidity in the test tubes.

Results
None of the three colloidal silver solutions tested
had any effect on the growth of the test organisms,
including Aspergillus niger, in the agar-well diffusion
assay. All of the test bacteria were sensitive to
ciprofloxacin, with zones of inhibition of 29–48mm
(after subtraction of the well diameter of 5mm), and
to one or more of the standard antibiotics.
Colloidal silver 22ppm also showed no bactericidal
activity in the phenol coefficient tests. Phenol
coefficients of Savlon for Staphylococcus aureus and
Pseudomonas aeruginosa were 3.75 and 1.11 respectively;
for ethanol they were 0.04 and 0.03.

Discussion and conclusion
These results show that colloidal silver does not
demonstrate any antibacterial potency when tested
in vitro using standardised methods.
Our results are in accordance with those of Spratt
et al., who reached the same conclusions with a different
set of bacterial isolates.16 In their study the
bactericidal effect of 5ppm colloidal silver, 2.25%
sodium hypochlorite, 0.2% chlorhexidine, 10%
iodine and phosphate-buffered saline as a control
was investigated against single-species biofilms of
Prevotella intermedia, Peptostreptococcus micros,
Streptococcus intermedius, Fusobacterium nucleatum
and Enterococcus faecalis. Hypochlorite, chlorhexidine
and iodine had a bactericidal effect against all
strains. Colloidal silver was generally ineffective,
even after one hour of contact with the biofilms.
We can only speculate about the positive laboratory
results presented on the internet. These might
be related to impurities of the solutions and the
presence of silver ions and oxidising agents resulting
from the ionisation of the water by an electric
current. Silver ions from silver salts such as silver
nitrate and from preparations such as silver sulphadiazine
that slowly release them have a strong bactericidal
activity.1-4 This is in contrast to the absence
of antimicrobial effects in metallic colloidal silver.
Silver,8 who performs fundamental research on
the genetics of silver resistance of silver-binding
bacteria, warned that ‘the wide and uncontrolled
use of silver products may result in more bacteria
developing resistance, analogous to the worldwide
emergence of antibiotic and other biocide-resistant
bacteria’.

Since colloidal silver did not show any antimicrobial
effect in vitro on common pathogenic microorganisms,
claims of its potency are misleading and
there is no place for it as an antiseptic.

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