You Are Determining the Number of Colony Forming Units (CFUs)

question 49

Multiple Choice

You are determining the number of colony forming units (CFUs) for Susan, who has a urinary tract infection (UTI) . You added 1 mL of Susan's urine sample to 99 mL of diluent, and spread 0.1 mL of that dilution on a culture medium. After appropriate incubation, you count 143 colonies on the plate. What was the concentration of bacteria in the original urine sample?

• A) 1.43 cells/ mL
• B) 1.43 × 102 cells/ mL
• C) 1.43 × 103 cells/ mL
• D) 1.43 × 105 cells/ mL
• E) Cannot be determined

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