Introduction:  The microbial world is very large. The vast majority of microbes have a neutral or positive effect on our existence, however; a small percentage of bacteria can cause disease. Some examples of bacteria that can cause disease are Escheichia coli, C600, or Staphylococcus, which is that strain used in our lab experiments. Many people die from bacterial and viral diseases; due to the existence of vaccines and antibiotics lethality from microbial disease has become much less common. " Antibiotics are substances produced by microorganisms that kill or inhibit other microorganism," meaning antibiotics help cure infectious disease.  Our experiments were designed to test if a substance known as Colloidal Silver has antibiotic properties. Colloidal silver has been classified as an antibiotic by manufacturers of this product, which by theory is able to kill bacteria and halt the spreading of other infectious diseases. There are claims that colloidal silver  can kill bacteria, viruses, yeasts, molds, fungi, and parasites. Colloidal silver has " pure silver electrically suspended in pure water" and is believed to have no side effects. Colloidal silver can be purchased in numerous ways, the easiest of which is logging onto the internet and visiting http://www.utopiasilver.com/. We will be using Colloidal silver in our experiments to test whether it truly does carry antibiotic property when compared to the three known antibiotics Kanamycin, Streptomycin, and Ampicillin. From our experimentation, it will be proven that colloidal silver does contain some antibiotic properties.

Materials & Methods: 

Culturing bacteria: One hundred microliters of C600 was pipetted and spread( the spreader was dipped in ethanol and ran through a flame from a bunson burner, to sterilize it), on Luria broth agar plates. The plates were incubated at 37°C overnight.

Testing for the antibiotic activity in colloidal silver: Two petri plates were cultured with C600 bacteria. Each plate was pipetted with one drop (50 microliters) of colloidal silver and placed in a uniform circle on the spread of the bacteria. The same procedure was repeated for the testing of Kanamycin, Streptomycin, and Ampicillin for the C600 plates. The plates were incubated at 37°C overnight. Signs of the cultured bacteria indicated that there was an absence of bacteria where the silver was pipetted, which implies that antibiotic properties are present.

Testing for number of bacteria present in the drosophila fly:  One hundred microliters of sterile water was added into an epindorf tube.  One fly was placed into the tube and with a sterile pestle, homogenized the fly repeatedly until the fly was evenly dispersed.  2.5 microliters of the homogenized fly was pipetted  and spread on the Luria agar plate.    These were incubated at 37°C and then the bacterial colonies present on the agar plate were counted. We then took the colonies, multiplied by a hundred, and then divided by 2.5 to calculate the number of bacteria in each fly.

Making fly food for colloidal silver and water: 30 milliliters of fly food from Carolina Biological were placed into two different tubes.  15 milliliters  of Colloidal silver was added to one of the tubes and shaken until hardened.  15 microliters of distilled water was added to the other tube, and shaken until hardened.

Culturing flies in colloidal silver and water:  The flies were anaesthetized with "Flynap" from Carolina Biological. With a paint brush  twenty flies were placed into tubes, ten were treated with colloidal silver and placed in the one tube.  The other ten (untreated) were placed into the other tube. The  tubes were then laid on their sides to prevent the flies from drowning in the  moist food solution..

Testing for the effectiveness of colloidal silver on bacteria from drosophila flies:  Six flies were taken from the tube with colloidal silver food, and then  each fly was placed in their own epindorf tube.  One hundred microliters of sterile water was added to each tube.  Three of those tubes were taken and the flies were homogenized.  The other three were centrifuged.  2.5 microliters of solution was pipetted (in a uniform circle), from each tube and spread on six Luria broth agar plates.  Six flies were then taken from the tube with water and  each fly was placed in their own epindorf  tube.  One hundred  microliters of sterile water was added to each tube.  The flies were homogenized in three of the tubes and the other three were centrifuged.  2.5 microliters of solution was then pipetted from each tube and spread on six Luria broth agar plates.  The colonies of the twelve different petri plates were counted, and  then the numbers were adjusted to calculate the number of bacteria in each fly. 

Results:  

The effects of colloidal silver on bacterial growth: Silver was tested against known antibiotics Kanamycin, Streptomycin, and Ampicillin. . The results showed that Kanamycin, Streptomycin, and Ampicillin killed the bacteria completely and in a uniform circle while colloidal silver only partially killed the bacteria in a small ring outside of the drop.

From these observations and the obvious appearance of the plates above, the conclusion is that colloidal silver is an inferior antibiotic when compared to Kanamycin, Streptomycin, and Ampicillin. These well known antibiotics completely wiped out bacteria when they were placed on the agar dishes, whereas colloidal silver partially killed the bacteria. Colloidal silver functioned at a lower rate then the other antibiotics and is thus seen as an inferior antibiotic.

The effects of colloidal silver in context of a living organism: (Figures below are adjusted for # of colonies present in solution)

The flies that are labeled as "homogenized" were ground up with a sterilized pestle in the epindorf tube and then 2.5 mcl of the solution was spread on the Luria broth plates with a sterilized glass spreader.  The bacterial colony growth was then counted, which gave us the figures below. The same was done for the flies "centrifuged" (these flies were centrifuged in epindorf tubes with water).

Flies homogenized in Silver averaged 21,453 colonies in the solution.

Flies homogenized in Water averaged 228,693 colonies in the solution.

Flies centrifuged from Silver averaged 306 colonies in the solution.

Flies centrifuged from Water averaged 573 colonies in the solution.

Our data from this experiment showed significant results regarding the use of colloidal silver.  Colloidal silver reduced the internal number of bacteria in drosophila flies by 91%.  This was a very significant figure and conclusions can be drawn that colloidal silver actually does have antibiotic properties that will reduce the number of bacteria present in living organisms.  Our centrifuged fly also had significant results; colloidal silver reduced the number of bacteria growth by 53% on the outside of the flies bodies.  The obvious conclusion that can be drawn from these experiments are that colloidal silver reduces the number of bacteria both externally (outside of the body) and internally (inside of the body) when regarding living organisms.  

Another key observation from the results was that colloidal silver was not harmful to living organisms.  Colloidal silver has been advertised as an antibiotic that has no harmful side effects whether taken internally or used externally.  This experiment proves this statement due to the fact that more of our flies actually died while in the water and food mixture than in the colloidal silver and food mixture.  The flies that were in the silver solution looked and behaved the same as the flies in the water solution and seemed to be just as energetic in their motions.  However, the fact that there were more deaths in the water and food mixture could have been due to a third variable, such as those flies could have just been older and on the brink of death already.  For the purposes of this study, third variables will not be considered and the conclusion is that colloidal silver is not toxic to living organisms. 

Discussion of Results: 

   The experiments listed above all somehow relate to the testing of colloidal silver as an antibiotic; however, the most important topics that  will be pursued in greater detail are: Does colloidal silver have the same killing power as other antibiotics?  Does colloidal silver reduce the number of bacteria in living organisms externally and internally?  Is colloidal silver toxic to living organisms?

  When we tested colloidal silver on cultures of C600 bacteria, we found that colloidal silver did, in fact, kill the bacteria in an antibiotic like fashion.  When we placed drops of the silver in the middle of the plates, we saw the silver partially killed bacteria in the center of the drop, but completely killed bacteria in a small ring around the center, usually .1cm. in diameter.  We concluded that colloidal silver had some antibiotic properties and that it was able to kill bacteria in a culture.  This does not mean, however, that silver kills with the same strength of ordinary antibiotics.  We tested Streptomycin, Kanamycin, and Ampicillin against the colloidal silver using the same procedures as we used in testing the silver in previous experiments.  We found that colloidal silver has nowhere near the same killing strength as these well-known antibiotics.  Even when we diluted Streptomycin, Ampicillin, and Kanamycin to a fraction of their normal strength, these antibiotics still killed much better than colloidal silver.  We concluded that colloidal silver has some antibiotic properties, but is inferior to these other antibiotics and even diluted mixtures of them.

  We also tested colloidal silver in living organisms, namely the drosophila fly.  We mixed colloidal silver in fly food and let the flies live in and eat this food for one week.  We took another group of flies and let them live in and eat fly food mixed with regular tap water for a week for comparison.  When we took our samples after one week, we found that colloidal silver significantly reduced the number of bacteria both internally and externally in these flies.  The flies that were eating the silver had far less bacteria inside of their bodies and outside as well. Of the flies that were homogenized, those that were from the silver solution had 91% less bacteria than the water. Of the flies that were centrifuged in the solution, those from the silver solution had 53 % less bacteria than the water solution. We concluded that colloidal silver actually does kill bacteria in living organisms, and also that it did a very good job at it as well.  We do not know if these same results could be replicated in other organisms, but it was evident that colloidal silver works very well to reduce the number of bacteria present internally and externally for drosophilae flies. The experiments done on the drosophilae flies acts as a model to what could be seen in other living organisms.

  The last topic  is the toxicity of colloidal silver.  When this experiment began, we weren’t sure if the mixture of colloidal silver in the food of these flies would be harmful to their health. The silver was not lethal to these flies and it seemed to have no effects on these flies other than significantly reducing the number of bacteria present in them.  After letting the flies live in and eat the silver for one week, the flies were behaving normal and looked just as energetic as the flies in the food mixed with water tube.  We found that more of the flies that were living in the water and food tube died than the ones living in and eating silver.  This doesn’t mean that the water is more toxic than the silver; of the flies that died, probably all of the deaths were due to natural causes.  But this does raise a question.  Did more of the flies in the silver live because of the reduced number of bacteria in their bodies make them healthier or was it just that the water mixture contained older flies that were on the brink of death anyway?  I have just proposed this idea, but have no means of answering it.  But either way, we concluded that the colloidal silver was not toxic in the drosophilae fly, and infer that it is not toxic to most living organisms. We already know that colliodal silver is not toxic when ingested by  humans, and there are claims that it improves health and cures disease. For further reading go to http://www.utopiasilver.com/. 

Page Counter: since 10/23/01
Date of last page update: 10/23/01
University of Redlands