At the end of this chapter, the reader should be able to do the following: 1. Calculate the colony forming units or concentration of bacteria per milliliter of sample in a urine specimen when using a calibrated loop. 2. Correlate the quantity of colony forming units from a urine culture with probability of urinary tract infection. A clean-catch urine specimen was obtained from a 42-year-old woman with a possible urinary tract infection. The urine was cultured using a 0.01-mL calibrated loop. After appropriate incubation, 8 colonies are counted. What is the patient’s CFU/mL, and is it indicative of a urinary tract infection? Since the 0.01-mL loop was used, the number of colonies, 8, is multiplied by 100, yielding 800 CFU/mL, or 8.0 × 102 CFU/mL. Since this is less than 103 CFUs of bacteria, the result is not indicative of a urinary tract infection. A clean-catch urine specimen was obtained from a 12-month-old boy with a possible urinary tract infection. The urine was cultured using a 0.01-mL calibrated loop. After appropriate incubation, 1245 colonies are counted. What is the patient’s CFU/mL, and is it indicative of a urinary tract infection? Since the 0.01-mL loop was used, the number of colonies, 1245, is multiplied by 100, yielding 124,500 CFU/mL, or 1.245 × 105 CFU/mL. Since this is more than 105 CFUs of bacteria, the result is indicative of a probable urinary tract infection.
Microbiology Laboratory
COLONY COUNTS
Example 11–1
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree