Saint Martin’s University Biology Journal
May 2006, Volume 1
Contrary to expectation, native nails that were washed had the highest average, and nails that were unwashed had the lowest average. When comparing acrylic (washed and unwashed) nails, washed acrylic nails had the highest average and unwashed acrylic nails had the lowest average. An analysis of variance (Minitab; Anova) showed that there was no significant difference between the number of bacterial colonies grown on a Petri dish from samples taken from the four groups (native nails unwashed, acrylic nails unwashed, native nails washed, and acrylic nails washed) (F=1.66; d.f.=3; P=0.195). In Figure 1, it is contrary to expected results that both washed native and acrylic nails contained more bacteria than both sets of nails unwashed. The error bars, which denote one standard deviation, demonstrated a large variation within each group between the number of bacterial colonies found on nails when they were unwashed, or washed. Figure 1 indicates that all nails after being incubated for 24 hours at 37°C yielded a
minimum of 1,000 bacterial colonies on a
Petri plate with nutrient agar.
spectrophotometer method, in which the concentration of bacterial cells was measured with light (transmittance, a set wavelength, and absorbance). The higher absorbance means more bacteria, and lower absorbance means fewer bacteria to absorb the light. The mean absorbance for acrylic nails was 0.4570, and the mean absorbance for acrylic nails was 0.223. The mean absorbance for acrylic nails was higher than the mean absorbance for acrylic nails. Since the error bars denoting the standard deviation overlap, there was no significant difference between the two groups of nails. Statistically, my null hypothesis is accepted. This means that there is no significant difference in bacterial growth between native and acrylic nails when absorbance was measured, even though the mean absorbance of both groups of participants appeared different (F=1.68; DF=1; P=0.214).
Figure 2. The average absorbance found for unwashed native nails and acrylic nails (unwashed) when measured with the spectrophotometer. Each error bar represents one standard deviation about the mean. One bar represents 10 native nail participants, and the other represents 8 acrylic nail participants, whose left hand was swabbed unwashed. The nutrient broth used for this method was incubated at 37°C for 24 hours.