(3) 3. There is concern that some fresh strawberries were contaminated with Listeria monocytogenes. Samples of the strawberries were taken and analyzed. The researcher collected the samples and then plated out 0.1ml/plate of ground strawberries diluted to 1/1000X. After time for growth the plates had the following colony numbers: Plate 1 – 122 colonies Plate 2 – 156 colonies Plate 3 - 98 colonies Calculate the number of CFU/mL in the strawberries. Give formula and include units in your answer. Focus ed States) D9 AON átv 24 T

(3) 3. There is concern that some fresh strawberries were contaminated with Listeria monocytogenes. Samples of the strawberries were taken and analyzed. The researcher collected the samples and then plated out 0.1ml/plate of ground strawberries diluted to 1/1000X. After time for growth the plates had the following colony numbers: Plate 1 – 122 colonies Plate 2 – 156 colonies Plate 3 - 98 colonies Calculate the number of CFU/mL in the strawberries. Give formula and include units in your answer. Focus ed States) D9 AON átv 24 T

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter26: Prokaryotes: Bacteria And Archaea

Section: Chapter Questions

Problem 8TYK

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1. An undercooked boiled egg was received in the microbiology laboratory with a request culture and identification. This egg was served in a pack lunch during a birthday party. All guests who ate this egg were brought to the hospital for vomiting and dehydration. Some had bouts of diarrhea. The signs and symptoms were short-lived after treatment was received. The egg was homogenized in tryptic soy broth. This was plated in sheep’s blood agar plate and MacConkey agar plate. After 24 hours of incubation, the following observations were noted: Sheep’s blood agar plate: 4+ (many) beta hemolysis, creamy white colonies MacConkey agar plate: no growth The gram stain result of the isolate yielded gram-positive cocci, mostly in clusters. If Staphylococcus aureus is suspected, list 3 tests that will be most relevant in its identification – i.e. to differentiate it from other gram-positive cocci
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Disinfectants, be they heat or radiation or chemicals, usually kill a constant proportion of the cells present per unit time if the cells are all equally susceptible. Hence, the term ‘log kill.’ The probability of death is constant over time given a ‘single hit.’ The more cells present at the start, the greater the number killed per unit time and the longer it will take to kill them ‘all.’ One decimal reduction is one log place (exponent). Log Nt = Log N0 – t/D. D is the time required for a log kill. A suspension of 105 CFU/mL of Salmonella is treated with bleach, and 90% of the cells are dead after 10 minutes. How many viable cells per mL would you expect after 30 minutes? Yes, the 30 minutes here implies 3 logs of killing. This is an excellent problem to use with the Death Equation because you can reason it through first, and then solve it using the equation.
1) Which of the following control agents help to be used to achieve sterility? - Virucide - Sporocide - Germicide - Bactericide - Fungicide
1. How is UV radiation a good type of control mechanism against microbial growth? Please explain what happens to the microbe and effects this control causes. 2. Suppose you do the Kirby-Bauer test on a hypothetical Staphylococcus species with penicillin and tetracycline. You record diameters of 20mm for tetracycline and 24mm for penicillin. Which antibiotic is most effective against this bacterium and why? Please explain and interpret these results. 3. Please provide the scientific name of your microbe that was used in the UV experiment (i.e. S. aureus). Compare your plates and interpret/analyze your results. Please discuss your findings and any patterns you were able to gather. 4. After performing the “Effects of Antiseptics & Disinfectants” lab which agent(s) showed potential to control S. marcescens growth? P. aeruginosa? Please explain why you believe these agent(s) work. 5. What purpose does water serve in the “Effects of Antiseptics & Disinfectants” lab? What did you…
6a. A sample is given to you that contains 6 million cells per ml. You must make a series of serial dilutions in order to get a countable number on a plate to prove that there are indeed 6 million cells per ml. The plate that you eventually put a sample of bacteria on must have between 10 and 100 colonies for ease of counting. What dilutions do you make to get this many colonies on a plate? How many colonies do you have on that plate? Show what dilutions you make (Write exactly how much liquid you move into each test tube and how much liquid was in the test tube, ex. Move 1 ml of culture into 9 ml of water – 10x dilution). Don’t forget to tell me how much liquid you eventually put on your plate. (If you want to draw something out, you could draw then take a picture of it with your phone and submit the image along with the worksheet). 6b. Do the same problem as in 6a, but now you have to do it in 3 test tubes or less. What dilutions do you do now? please use drawings to help…
1. How is UV radiation a good type of control mechanism against microbial growth? Please explain what happens to the microbe and effects this control causes. 2. Suppose you do the Kirby-Bauer test on a hypothetical Staphylococcus species with penicillin and tetracycline. You record diameters of 20mm for tetracycline and 24mm for penicillin. Which antibiotic is most effective against this bacterium and why? Please explain and interpret these results.
1. Why do you think the 5% sheep blood agar was selected for the culture of mouth bacteria?
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1) would you describe the contents of the soil-inoculated broth as being a “pure culture”? Why or why not? 2) How did the uninoculated broth differ in appearance from the broths inoculated with E. Coli and M. Luteus? And then how could you tell if a supposedly sterile, uninoculated broth was contaminated? Please explain in detail and highlight the important parts cuz I am confused and need help! Thanks