Science Fair Project- Analysis & Discussion

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Analysis & Discussion
The primary objective of this investigation was to test ultraviolet radiation as an alternative disinfectant for Acanthamoeba in its more resistant cyst form. A previous study had already shown that multipurpose solutions were ineffective compared to hydrogen peroxide based systems at eliminating Acanthamoeba trophozoite contaminations.5 This was a follow-up to that study. Another goal of this study was to test the effectiveness of hydrogen peroxide in eliminating Acanthamoeba cysts as well. Since trophozoites are the more susceptible form of Acanthamoeba, multipurpose solutions tested previously were not evaluated against cysts because they are not effective at eliminating the less resistant form of the organism. From prior knowledge, numerous studies, and from current commercial applications, it has been demonstrated that ultraviolet radiation is a reliable source for disinfecting microorganisms. More specifically, the UVC wavelength (200-260 nm) is microbicidal as compared to other wavelengths.8, The currently available system for contact lens disinfecting using UVC is called the PuriLens System. Only a single published report concerning the effectiveness of this system showed its limited abilities eliminating Acanthamoeba cysts.15 In general, there have been very few studies that tested any type of protozoan cyst sensitivity to UV radiation.8,9 The few studies that have been performed implied that Acanthamoeba cysts are among the most hardy cyst forms and require longer exposure and a higher concentration of UV radiation. 8,9 An analysis of the data showing growth or no growth allowed several observations and conclusions to be made. It seemed that the PuriLens system did an adequate job of disinfecting both Acanthamoeba cysts and trophozoites since no growth appeared on the plates at any time period. The hydrogen peroxide based system also showed satisfactory disinfection of cysts since again no growth was evident. The homebuilt UV radiator did not eradicate Acanthamoeba cysts with exposure time for less than 15 minutes. The data suggested that Acanthamoeba cysts need at least 15 minutes or more of exposure to UVC radiation in order for complete disinfection. The growth on the plates at 24 days was confirmed to have decreased significantly from the growth shown at ten days for all of the plates having growth. One problem noted in the PuriLens system before the experiment was that the contact lenses were not being directly exposed to UVC light. However, because the PuriLens system has an agitator, the organisms, sticking to the contact lens are supposed to be dislodged into the solution and then would be in the direct path of the emitted UVC photons. The homebuilt UV radiator was the alternative in order to compare whether or not this would affect the disinfection process of the contacts. The contact lenses in the homebuilt radiator were directly exposed to the UV lamp unlike the PuriLens system, where the contact lenses are slightly blocked from the UV lamp. There was at least one significant observation of this study that could have altered the results and would need to be addressed in future testing of these disinfecting methods. This observation concerned the amount of growth on the control plates for both cyst and trophozoites. For this study, it was noticed that on the control plate there was a rather small amount of growth on the plates compared to the previous study. Several factors may explain this observation. The sample of Acanthamoeba that was delivered may not have been properly handled while being delivered. Since the product was delivered frozen on dry ice and any deviation in the proper thaw time could have affected how many Acanthamoebas were alive, which therefore would have altered the concentration of Acanthamoeba in both the encystation and Peptone Yeast Glucose (PYG) medias....
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