Enumeration of Bacteria PDF

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Enumeration of Bacteria...

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MBIO 2815 Fall 2020

Meet Patel

Name:__________________________________________

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Section #:___________________

ENUMERATION OF BACTERIA ASSIGNMENT (25 pts) Due Monday or Tuesday (Sept. 14th or 15th) at 11:59 pm Using Table 1 that you completed in the results sheet, answer questions 1 and 2 below. 1. Which plate would you use to calculate the CFU/mL of the sample? Explain your choice. (1 pt)

I would choose a plate that appears to have between 30 and 300 colonies. A plate having 30-300 colonies is chosen because this range is considered statistically significant. If there are less than 30 colonies on the plate, small errors in dilution technique or the presence of few contaminants will have a drastic effect on the final count. If there are more than 300 colonies on the plate, there will be poor isolation of colonies as they would be grown together and also they will be to numerous to count (TNTC).

2. Calculate the CFU/mL of the sample from the plate you have chosen. SHOW ALL YOUR WORK AND USE SCIENTIFIC NOTATION WHEN WRITING YOUR ANSWER. (3 pts)

Formula for samples CFU/mL = (# of colonies) / (dilution factor X volume plated) Number of colonies on plate chosen = 208 Dilution factor of the plate: 10^-7 Voulme plated = 0.1 mL CFUs/mL = 208 / (10^-7 x 0.1) Final Answer: Sample plates CFUs/mL = 2.08 X 10^10 CFU/mL.

Using Table 2 that you completed in the results sheet, answer questions 3 and 4 below. 3. Using Table 2 you completed in the results sheet, calculate the original cell density (OCD) of EACH colony type in the “urine” sample. SHOW ALL WORK AND USE SCIENTIFIC NOTATION WHEN WRITING YOUR ANSWER(S). (3 pts)

OCD = # of colonies / loop volume (ml), where Volume of loop used = 0.01 ml volumetric loop. Description of colony : Small white colonies Number of colonies =96 OCD (small white colonies) = 96/0.01 therefore, OCD = 9.6 x 10^3 CFU/mL. Description of colony: Large yellow colonies Number of colonies = 26 OCD (large yellow colonies) = 26/0.01 therefore, OCD = 2.6 x 10^3 CFU/mL.

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MBIO 2815 Fall 2020

4. Based on the results you obtained, would you diagnose the person who provided this “urine” sample as having a urinary tract infection (UTI)? Explain why or why not. (1 pt)

No, from our results we can say that the person does not have UTI, since the colony type has < 10,000 CFU/mL which is likely to be due to normal flora contimination How to tell if the person has UTI: If a colony type has >10,000 CFU/mL the patient is diagnosed as having a UTI, the bacterial species is identified and its antibiotic resistance determined

Using Table 3 that you completed in the results sheet, answer question 5 below. 5. Based on the data obtained from Additional Exercise 8-11 (Soil Microbial Counts), which of the three categories of microorganisms examined was most prominent in soil sample #1 and which of the three categories of microorganisms examined was most prominent in soil sample #2? Indicate ONE environmental factor that could potentially change/effect the relative proportions of the microorganisms found in the soil. (2 pts)

Actinobacteria species was most prominant in soil sample #1. “Simple” Soil Bacteria was most prominant in soil sample #2. One environmental factor that could potentially change/effect the relative proportions of the microorganisms found in the soil is the soil-layer from which the soil sample is collected.

6. Congratulations, you are a nurse in a neonatal intensive care unit (NICU)! In this unit, many antibiotics need to be diluted before being administered because of the low body weight of infants. To treat a newborn with bacterial sepsis (i.e., infection of the blood) you are told to prepare an antibiotic solution. You are given a bottle that contains 17.34 mL of sterile saline and a bottle that contains 3 mL of an antibiotic solution and are told to make a 1:17 dilution of the antibiotic solution using all the sterile saline you have. How much antibiotic solution would you need to add to the bottle of sterile saline to produce the correct dilution? SHOW ALL WORK WITH THE FINAL ANSWER ROUNDED UP TO 2 DECIMAL PLACES. (3 pts)

Since, we need to make 1:17 diltion of antibiotic solution, we have to add 1 mL of antibiotic soltion into (17-1=16mL) 16 mL of saline to form total 17 mL of final volume. So, for 17.34 mL bottle of sterile saline we would need: Amount of antibiotic solution needed (mL) = 17.34 mL x 1 mL / 16mL Amount of antibiotic solution needed (mL) = 1.08 mL.

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MBIO 2815 Fall 2020

7. You work in one of the quality control labs at Hiland Dairy Foods. Specifically, your job involves monitoring the total bacterial counts of unpasteurized and pasteurized Grade A milk in order to ensure that the manufacturing process is operating properly. The figure below shows the procedure you used and the results you obtained after testing a milk sample before and after pasteurization.

Based on the figure and the information provided answer the following questions: i.) What was the concentration of bacteria in the milk sample BEFORE pasteurization? SHOW ALL WORK WITH THE FINAL ANSWER WRITTEN USING SCIENTIFIC NOTATION (should have 3 significant figures). (3 pts)

Colony number selected which is [30 ≤ x ≤ 300] Concentration of bacteria in the milk sample BEFORE pasteurization: Bacteria concentaration in CFU/mL = (# of colonies) / (amount plated x dilution factor) = 161 / 0.5 mL x 10^-3 Bacteria concentaration in CFU/mL BEFORE pasteurization = 3.22 x 10^5 CFU/mL.

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MBIO 2815 Fall 2020

ii.) What was the concentration of bacteria in the milk sample AFTER pasteurization? SHOW ALL WORK WITH THE FINAL ANSWER WRITTEN USING SCIENTIFIC NOTATION. (3 pts)

Colony number selected which is [30 ≤ x ≤ 300] Concentration of bacteria in the milk sample AFTER pasteurization: Bacteria concentaration in CFU/mL = (# of colonies) / (amount plated x dilution factor) = 177 / 0.6 mL x 10^-2 Bacteria concentaration in CFU/mL AFTER pasteurization = 2.95 x 10^4 CFU/mL.

iii.) If federal regulations require no more than 2.5x105 CFU/mL of bacteria in milk prior to pasteurization and no more than 2.5x104 CFU/mL after pasteurization, should the milk you sampled be bottled and sold for consumption? (1 pt)

No, the milk we sampled should not be bottled and sold for consumption since it did not met federal regulation requirements.

iv.) Your co-worker did the identical procedure with the same milk sample but obtained significantly different colony counts. The only notable difference was that you used 5 pipet tips when making the initial dilution series while your co-worker used a single pipet tip. Knowing this would you expect your co-worker’s colony counts to be higher or lower than those you obtained? Explain why. (2 pts)

Since the co-worker used the single pipet tip when making initial dilution series, the colony count would be higher than the one’s obtained be me. Changing pipette tips between each serial dilution is important because trace amounts of solutions will stick to the side of the pipette tip, which can affect concentrations of dilutions and likewise affect colony count.

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MBIO 2815 Fall 2020

8. Many chemotherapy drugs used in the treatment of cancer are extremely toxic and must be diluted prior to being given to patients. You have a bottle that contains 4.631 mL of Taxol®, a drug that is used to treat ovarian and breast cancer, and a bottle that contains 300 mL of sterile saline. How much sterile saline would you need to add to the bottle containing the drug to achieve a 1:32 dilution of the anti-cancer drug? SHOW ALL WORK WITH THE FINAL ANSWER ROUNDED UP TO 2 DECIMAL PLACES. (3 pts)

Since, we need to make 1:32 diltion of anti-cancer drug, we have to add 1 mL of anti-cancer drug (Taxol®) into (32-1 = 31mL) 31 mL of sterile saline solution to form total 32 mL of final volume. If, 1mL anti-cancer durg = 31 mL sterile saline then, 4.631 mL anti-cancer durg bottle = (x =?) mL sterile saline Amount of sterile saline needed (mL) = (4.631 x 31)/ 1 mL Amount of sterile saline needed (mL) = 143.56 mL So, for 4.631 mL bottle of anti-cancer drug we would need to add 143.56 mL of sterile saline solution.

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