a. If you placed 10g of soil in 90 ml of sterile saline, what is your dilution?

Question

a. If you placed 10g of soil in 90 ml of sterile saline, what is your dilution? b. from this blank, remove 1ml and place it into a 99ml blank. Now what is your dilution? c. Remove 1 ml from this 2nd blank and place it into a 3 blank (99ml). What is your dilution 3. now? d. you plate 1mL from this last blank, and 0.1ml onto another plate. What are your dilutions on each of these plates? e. if you counted 367 colonies on your less dilute plate, and 41 colonies on the higher dilution, what is your final cell density in the soil sample? (1 point per blank) _ and respectively. 4. Diagram how you would plate onto MacConkey Agar at 10, 10, and 10 from a patient urine specimen. Include all volumes transferred, volumes in your blanks, and dilution values. (6 pts) You are working as an RN, and one of the physicians on your floor, Dr. Falkirk, asks you to dilute a stock vial of Ciprofloxacin for a patient. The starting concentration is 450 mg/mL. However, the antibiotic is to be administered at 90 ug/mL in a total volume of 10cc. Diagram/describe how you would do this. (8) 5.

Explanation / Answer

3)a) Dilution = 10mg / 90 ml= 0.11mg/ml

b)1 ml of above is diluted in 99 ml so, now the dilution is 0.11mg/100ml (= 0.0011mg/mL) since the total volume is 100 ml

c)1 ml from second blank is added to another 99 ml so the dilution now is 0.0011mg/100 ml (0.000011mg/mL).

d) 1 mL from the last blank means 0.000011mg of soil sample and 0.1mL means 0.0000011mg of soil sample.

e) If 0.000011mg of soil sample has 367 colonies then 10mg will have (367 x 10) / 0.000011= 3.33 x 108 .

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