Urine culture is often used for urinary system infection, which is very important to guide the application of antibiotics. It is sometimes difficult to make a definite diagnosis only by symptoms, signs and routine urine examination, and urine culture examination is needed as the basis for diagnosis and treatment. Take clean midcourse urine. If E.coli is greater than 105/ ml, it is called genuine bacteriuria, and less than 104/ ml is urine pollution. The accuracy of diagnosing urinary tract infection is 80% when the female urine count is greater than 107 ml at one time, and 95% when the urine count is greater than 105/ ml at two different times. When the male is greater than 104/ ml, it is urinary tract infection. If the number of cocci is greater than 104/ ml, it can also be diagnosed as true bacteriuria. The results of urine culture may be influenced by many factors, which may not be accurate or reflect the real situation correctly. Generally, there are the following aspects: 1. Improper specimen collection method: urine should be collected in sterile containers to clean the middle urine culture, especially for women, to prevent secretions from polluting the specimens, and also to prevent disinfectants from mixing with urine during vulva disinfection. If the operation is not standardized, it may affect the performance. 2. Specimens should be kept for too long: the urine should be collected fresh and kept for no more than 1 hour, otherwise, bacteria will multiply in large numbers and false positives will easily occur. 3. Drug factors: antibiotics were used before urine culture, and the positive rate was greatly reduced. 4. Influence of drinking water: The urine stays in the bladder for too short a time, or drinking too much water dilutes the bacteria in the urine, which may affect the results. 5. Affected by the course of disease: bacterial excretion of urinary tract infection can be intermittent, such as chronic pyelonephritis without acute attack, and urine culture can be negative. 6. Operational technical factors: technical errors or mistakes. 7. Strain type: Different strains will also affect the results. 8. Influence of lesion site: Hematogenous acute glomerulonephritis, formation of small abscess in renal parenchyma and chronic pyelonephritis tend to be cured. Because renal parenchymal lesions still exist, urine culture bacteria are often positive. In a word, urine culture should be combined with clinic, and it needs to be checked many times, so as to enhance the accuracy as much as possible before applying antibiotics.