Antibacterial Resistance Lab Report
Vu Nguyen BIOL 1003/22 ANTIBIOTIC RESISTANCE LAB REPORT Introduction Natural selection is a non-random process in which individual with favorable traits for the environment will likely survive and reproduce than those without these traits. In contrast to Natural selection, Artificial selection is the process in which desired traits are intentionally chose to breed among individuals. Antibacterial resistance is the process in which strong and highly resistant bacterial is selected against weaker bacterial. The selected bacterial then continue to reproduce and create a stronger bacterial population, which is resistant to antibacterial materials. Antibacterial resistance is the result of natural selection because the bacterial with highly adaptable
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and stronger traits are selected against weaker bacterial. This phenomenon affects highly the way people use medicine and chemicals to treat bacterial. In daily life there are hundreds of antibacterial products are used to kill germs but do these products really work the way they supposed to is a big question because the way these products work is just to select strong bacterial, which will reproduce stronger and more resistant population, against weak bacterial. Thus, the higher concentration of antibiotic is used, the more resistant bacterial is. To be more specific, E. Coli (a type of bacteria) will become more resistant to triclosin (an antibacterial chemical) throughout the four rounds of the experiment. Methods To test the hypothesis, we use a lab experiment containing two parts. The first part of the lab is planting bacterial E. Coli and the second part is designed to select for the bacteria’s resistance. This experiment is replicated 4 times, which is each called a round, in one week. In part one, 50μL of E. Coli is taken from a tube of tryptic soy broth and planted onto a plate with soy agar, where the E. Coli grow and reproduce. Then the plate will be labeled in a way that reflects its source tube. After that, the E. Coli is spread around the plate using a blue lazy L. A 6mm paper disk will be dip into either triclosan or alcohol solution and then placed in the center of the plate. The 48 plates with
triclosan treated papers are experimental group and those four plates with alcohol treated papers are control group.
After finish placing paper disks, the plates will be closed, sealed and incubated for 24 hours. This is the end of part one. Part two of this experiment dealing with selecting for resistance. This begins with measuring the zone of inhibition, where no bacteria can grow just around the paper disc, of each plate in millimeters to see how resistant the bacteria are. Then the experimenter takes a tube of tryptic soy but no E. Coli and an incubated plate. The tube needs to be correctly labeled with the culture type and the plate number. After that, the bacteria lying along the colonies along the inner edge of the zone of inhibition is selected and taken out using a sterile inoculating loop. With the bacteria on, the sterile inoculating loop will be swirled in the tube of tryptic soy broth. After 30 seconds to a minute, the experimenter discards the inoculating loop and tighten the lid on the loop, leaving a quarter of it loosen, and secure the tube with a small tape. The tube then will be incubated for 24 hours. This is the end of part two. After 24 hours, the experiment is repeated, using the results from the end of the previous part two as the insert for the beginning of the new part one. The independent variable here is the exposure to triclosin or the rounds and the dependent variable is the diameter of the zone of inhibition. Results For the experimental …show more content…
group, the average diameters of the 48 plates with triclosin paper discs after round one, round two, round three, and round four are 26.2 mm, 19.6 mm, 15.4 mm, and 11.8 mm respectively. For the first round, the diameters of the zone of inhibition range from 7mm to 45 mm. The second round’s results range from 7mm to 36 mm but there are 2 bottles with no records. The diameters of the zone of inhibition range from 7mm to 36mm with two data missing. The data for round four range from 7mm to 28mm with 2 data missing. The average diameters of the zone of inhibition decrease steadily from round to round. For the control group, the average diameters of the four plates with alcohol treated paper discs after four rounds are 10.1 mm, 7.6 mm, 7.2 mm, and 7.1 mm respectively. For the first round, the samples’ diameters range from 7 mm to 20 mm. The second
round’s diameters range from 7 mm to 11.5 mm. Round 3’s data range from 7 mm to 9 mm. and round 4’s data range from 7 mm to 8 mm. There is no data missing for this group of the experiment. The average diameters for the control group decrease slightly from round to round. Comparing the experimental group and the control group’s data, there is a big gap between the diameters of the zone of inhibition of the experimental group and those of the control group. The graph describing the result of the experiment for both experimental and control groups is presented below.
30
Average Diameter of the Zone of Inhibition
Control group
25 Average diameter (mm)
20 Experimental group 15
10
5
0 Round 1 Round 2 Rounds Round 3 Round 4
Analysis Looking at the data, it is easy to see that the average diameter of the zone of inhibition decreases after each round for the experimental group. The degree of decrease is fairly high. The decrease in size of the zone of inhibition suggests that 1) after each round, there is more bacteria can survive and penetrate further into the zone of inhibition; 2) the bacteria grows stronger after each round; and 3) after each round, the bacteria become more resistant to triclosin. This phenomenon can be explained in terms of selection. The process of taking bacteria around the ring of the zone of inhibition on the
plate is the process of selecting the strongest and most resistant bacteria.
Through four rounds of this experiment, the strongest bacteria were continuously selected against the weaker ones hence resulted in the size of the zone of inhibition becoming smaller and smaller. For the control group, the size of the zone of inhibition from the beginning had been significantly smaller than that of the experimental group. Throughout the experiment, the zone of inhibition did decrease but just for a relatively small degree. This suggests that the experiment was valid in testing antibiotic resistance. Among the data set, there are some potential outliers. For an item to be considered a potential outlier in this experiment it has to be greater or less than three standard deviations from the mean diameter for each round. In the experimental group, the potential outlier for round 3 is 36 mm and those for round 4 are 25 mm, 27 mm and 27 mm. In the control groups, there is one potential outlier for round 1, which is 20 mm, one potential outlier for round 3, which is 9 mm and two potential outliers for round four, which are 7 mm and 9 mm. The existence of these outliers may due to the experimenters’ not getting the exact bacteria from the edge of the zone of inhibition, closing the lid of the tube too tight so the E. Coli could not fully grow, or difference of the concentration of triclosin in some tubes. However, the number of these potential outliers is relatively insignificant to the
sample size so it is reasonable to conclude that the experiment is valid and reliable. To sum up, the result does support the hypothesis, which claims that E. Coli will become more and more resistant to triclosin throughout the experiment. Conclusion Based on the result and the analysis of this experiment, it is clear that using triclosin or antibiotic substance results in stronger resistance among bacteria and may create new superior population of bacteria. This result can also be linked to real-life application, when people use antibacterial products to clean themselves as well as their furniture and stuffs. This act of using antibiotic substance, in contrast with what the advertisements say, actually enhance bacteria’s resistance and the improve the
strength of bacteria. Thus, using antibacterial substances may not be a really good way to fight against bacteria; instead, using non-antibacterial substances is enough to maintain daily sanitization.
and stronger traits are selected against weaker bacterial. This phenomenon affects highly the way people use medicine and chemicals to treat bacterial. In daily life there are hundreds of antibacterial products are used to kill germs but do these products really work the way they supposed to is a big question because the way these products work is just to select strong bacterial, which will reproduce stronger and more resistant population, against weak bacterial. Thus, the higher concentration of antibiotic is used, the more resistant bacterial is. To be more specific, E. Coli (a type of bacteria) will become more resistant to triclosin (an antibacterial chemical) throughout the four rounds of the experiment. Methods To test the hypothesis, we use a lab experiment containing two parts. The first part of the lab is planting bacterial E. Coli and the second part is designed to select for the bacteria’s resistance. This experiment is replicated 4 times, which is each called a round, in one week. In part one, 50μL of E. Coli is taken from a tube of tryptic soy broth and planted onto a plate with soy agar, where the E. Coli grow and reproduce. Then the plate will be labeled in a way that reflects its source tube. After that, the E. Coli is spread around the plate using a blue lazy L. A 6mm paper disk will be dip into either triclosan or alcohol solution and then placed in the center of the plate. The 48 plates with
triclosan treated papers are experimental group and those four plates with alcohol treated papers are control group.
After finish placing paper disks, the plates will be closed, sealed and incubated for 24 hours. This is the end of part one. Part two of this experiment dealing with selecting for resistance. This begins with measuring the zone of inhibition, where no bacteria can grow just around the paper disc, of each plate in millimeters to see how resistant the bacteria are. Then the experimenter takes a tube of tryptic soy but no E. Coli and an incubated plate. The tube needs to be correctly labeled with the culture type and the plate number. After that, the bacteria lying along the colonies along the inner edge of the zone of inhibition is selected and taken out using a sterile inoculating loop. With the bacteria on, the sterile inoculating loop will be swirled in the tube of tryptic soy broth. After 30 seconds to a minute, the experimenter discards the inoculating loop and tighten the lid on the loop, leaving a quarter of it loosen, and secure the tube with a small tape. The tube then will be incubated for 24 hours. This is the end of part two. After 24 hours, the experiment is repeated, using the results from the end of the previous part two as the insert for the beginning of the new part one. The independent variable here is the exposure to triclosin or the rounds and the dependent variable is the diameter of the zone of inhibition. Results For the experimental …show more content…
group, the average diameters of the 48 plates with triclosin paper discs after round one, round two, round three, and round four are 26.2 mm, 19.6 mm, 15.4 mm, and 11.8 mm respectively. For the first round, the diameters of the zone of inhibition range from 7mm to 45 mm. The second round’s results range from 7mm to 36 mm but there are 2 bottles with no records. The diameters of the zone of inhibition range from 7mm to 36mm with two data missing. The data for round four range from 7mm to 28mm with 2 data missing. The average diameters of the zone of inhibition decrease steadily from round to round. For the control group, the average diameters of the four plates with alcohol treated paper discs after four rounds are 10.1 mm, 7.6 mm, 7.2 mm, and 7.1 mm respectively. For the first round, the samples’ diameters range from 7 mm to 20 mm. The second
round’s diameters range from 7 mm to 11.5 mm. Round 3’s data range from 7 mm to 9 mm. and round 4’s data range from 7 mm to 8 mm. There is no data missing for this group of the experiment. The average diameters for the control group decrease slightly from round to round. Comparing the experimental group and the control group’s data, there is a big gap between the diameters of the zone of inhibition of the experimental group and those of the control group. The graph describing the result of the experiment for both experimental and control groups is presented below.
30
Average Diameter of the Zone of Inhibition
Control group
25 Average diameter (mm)
20 Experimental group 15
10
5
0 Round 1 Round 2 Rounds Round 3 Round 4
Analysis Looking at the data, it is easy to see that the average diameter of the zone of inhibition decreases after each round for the experimental group. The degree of decrease is fairly high. The decrease in size of the zone of inhibition suggests that 1) after each round, there is more bacteria can survive and penetrate further into the zone of inhibition; 2) the bacteria grows stronger after each round; and 3) after each round, the bacteria become more resistant to triclosin. This phenomenon can be explained in terms of selection. The process of taking bacteria around the ring of the zone of inhibition on the
plate is the process of selecting the strongest and most resistant bacteria.
Through four rounds of this experiment, the strongest bacteria were continuously selected against the weaker ones hence resulted in the size of the zone of inhibition becoming smaller and smaller. For the control group, the size of the zone of inhibition from the beginning had been significantly smaller than that of the experimental group. Throughout the experiment, the zone of inhibition did decrease but just for a relatively small degree. This suggests that the experiment was valid in testing antibiotic resistance. Among the data set, there are some potential outliers. For an item to be considered a potential outlier in this experiment it has to be greater or less than three standard deviations from the mean diameter for each round. In the experimental group, the potential outlier for round 3 is 36 mm and those for round 4 are 25 mm, 27 mm and 27 mm. In the control groups, there is one potential outlier for round 1, which is 20 mm, one potential outlier for round 3, which is 9 mm and two potential outliers for round four, which are 7 mm and 9 mm. The existence of these outliers may due to the experimenters’ not getting the exact bacteria from the edge of the zone of inhibition, closing the lid of the tube too tight so the E. Coli could not fully grow, or difference of the concentration of triclosin in some tubes. However, the number of these potential outliers is relatively insignificant to the
sample size so it is reasonable to conclude that the experiment is valid and reliable. To sum up, the result does support the hypothesis, which claims that E. Coli will become more and more resistant to triclosin throughout the experiment. Conclusion Based on the result and the analysis of this experiment, it is clear that using triclosin or antibiotic substance results in stronger resistance among bacteria and may create new superior population of bacteria. This result can also be linked to real-life application, when people use antibacterial products to clean themselves as well as their furniture and stuffs. This act of using antibiotic substance, in contrast with what the advertisements say, actually enhance bacteria’s resistance and the improve the
strength of bacteria. Thus, using antibacterial substances may not be a really good way to fight against bacteria; instead, using non-antibacterial substances is enough to maintain daily sanitization.