Urine is normally sterile. However, in the process of collecting the urine, some contamination from skin bacteria is frequent. For that reason, up to 10,000 colonies of bacteria/ml are considered normal. Greater than 100,000 colonies/ml represents urinary tract infection.Any amount of bacteria in the urine may suggest UTI in a symptomatic patient, but the threshold for the classic definition of bacteriuria is 5+, which is roughly equivalent to 100,000 colony-forming units (CFUs)/mL