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Saint Martin’s University Biology Journal

with nail cosmetics. My goal was to compare bacteria in both acrylic and native nails, as well as observe which type of nail contains the most bacteria.

Quantitative Plating

The techniques research are taken from

for this method of Brown (2005). The

materials I used to prepare were: Ward’s nutrient containing the ingredients

the Petri dishes agar (80 ml, of 3g/L Bacto

peptone, and 15 g/L of Bacto agar) for testing the growth of bacteria on, 40 Petri dishes to pour nutrient agar in for testing of the growth of bacteria, an incubator, a hot plate for boiling the agar mixture, and an autoclave to sterilize the nutrient agar. I mixed the 80 ml of nutrient agar for 40 Petri

dishes. Then putting it into at 121°C, 15

I sterilized the nutrient agar by the Tuttnauer 2540E autoclave psi for 15 minutes. After the

agar had the Petri collected

cooled slightly, it was poured into dishes, and allowed to solidify. I samples from my participants from










2006. All the nails participants were

on the left hand

of my

swabbed with


swabs, and then the cotton to streak a Petri dish.




Next, I swabbed underneath all the nails of their right hand, and transferred the entire swab to the test tubes containing nutrient broth, described in method 2. Finally, I asked my participants to wash their hands. Upon returning from washing their hands, I gently swabbed underneath all the nails of both their left and right hand, using the swab from the left hand to swab the Petri dish and placed the swab from the right hand in a test tube with nutrient broth. These were my samples for washed hands. Afterwards, I incubated the Petri dishes and test tubes at 37°C for 24 hours. Individual bacterial colonies were then counted from each Petri dish. Then the Lab-Line Instruments, Inc. Colony Counter machine


May 2006, Volume 1

was used to count bacterial colonies. The data I collected after counting the bacterial colonies was analyzed by using the Minitab program (Minitab, Inc., 2005) (ANOVA; Tukey’s family error rate) to get statistical analysis.

Optical Density This method of quantifying bacteria in both acrylic and native nails also is from

Brown (2005). spectrophotometer,



refers to which

the the

concentration of bacterial cells is measured using light. Nutrient broth was prepared by adding 100 ml of distilled H20 to 80 grams of Bio Pro Premium nutrient broth which contains beef extract, and bio-gel peptone. The broth was poured into 45 test tubes, with 4 ml in each tube. The tubes were sterilized in an autoclave for at least 15 minutes at 121° C, and 15 psi. The broth was then removed from the autoclave and stored in a refrigerator at 4° C until needed for optical density measurements. I collected bacteria from participants with acrylic and native nails for this method by swabbing underneath all the nails on their right hand. After the nails were swabbed, the swab was transferred to the test tube containing nutrient broth. The culture collected in the test tubes was incubated at 37°C for 24 hours to allow bacteria to grow. Bacterial growth was then measured by using the Spectronic 20 Bausch & Lomb spectrophotometer, and recording the optical density for each sample at 480 λ. Afterwards, I took my data that I recorded, and used the

Minitab program (Anova; Tukey’s statistical analysis.

(Minitab, Inc., 2005) family error rate) for


As a result of using the Counting Bacterial Method (method 1) and Spectrophotometer method (method 2) to gather my data, I found there was no

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