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Bacterioscopic examination of urine sediment

Alexey Kryvenko, medical expert
Last reviewed: 05.07.2025

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Bacteriuria is the detection of bacteria in urine. Bacterioscopic examination of urine provides minimal clinical information for the diagnosis of urinary tract infections, so cultural methods are used. The latter allow not only to identify the type of pathogen, but also to determine the bacterial count (the number of pathogens in 1 ml of urine). Asymptomatic bacteriuria is the detection of ≥10 ⁵ microbial bodies of the same microorganism in 1 ml of urine in 2 consecutive tests performed at an interval of more than 24 hours. According to the "Recommendations of the European Association of Urologists for the Treatment of Urinary Tract Infections and Reproductive System Infections in Men", clinically significant bacteriuria in adults is considered to be:

≥10 ³ microbial bodies in 1 ml of midstream urine in women with acute uncomplicated cystitis;
>10 ⁴ microbial bodies in 1 ml of midstream urine in women with acute uncomplicated pyelonephritis;
>10 ⁵ microbial bodies in 1 ml of midstream urine in women or >10 ⁴ microbial bodies in 1 ml of midstream urine in men (or in urine obtained using a catheter in women) with complicated urinary tract infection (acute cystitis and pyelonephritis);
any amount of bacteria in urine obtained by suprapubic bladder puncture.

A urine culture test with determination of bacterial count is not a mandatory test method for women with uncomplicated cystitis. It is indicated together with determination of the sensitivity of isolated pathogens to antibacterial drugs if cystitis symptoms persist or recur for 2 weeks. A urine culture test should be performed in patients with acute pyelonephritis.

Bacteriological diagnostics of urinary tract infections in pregnant women has its own characteristics. Most women develop bacteriuria before pregnancy. Acute pyelonephritis develops in 20-40% of women with asymptomatic bacteriuria during pregnancy. The frequency of false-positive results of a single culture study of the middle portion of urine can reach 40%. In this regard, all women with a positive bacteriological study should undergo a repeat urine culture after 1-2 weeks, paying special attention to the toilet of the external genitalia before urination. After completion of treatment, a urine culture study is performed after 1-4 weeks, and again before childbirth.

In children, the diagnosis of urinary tract infection is based on the following criteria.

When sowing urine from a urine collector, only a negative result is considered significant.
Detection of any number of bacteria in urine obtained by suprapubic bladder puncture.
Detection of coagulase-negative staphylococci in urine in quantities of >300 CFU/ml.
Detection of bacteria in urine obtained using a catheter in an amount of 10 ⁴ -10 ⁵ CFU/ml.
In midstream urine testing: detection of pathogens in quantities of 10 ⁴ CFU/ml in patients with symptoms of urinary tract infection or 10 ⁵ CFU/ml in 2 urine samples collected more than 24 hours apart in children without symptoms of urinary tract infection.
Significant pyuria; detection of 10 leukocytes/ml urine in combination with bacterial counts of 10 ⁵ -10 ⁴ CFU/ml in catheterized urine in febrile children allows differential diagnosis between infection and contamination.
Detection of N-acetyl-beta-glucosaminidase in urine is a marker of renal tubular damage; its content also increases with vesicoureteral reflux.

To detect tuberculosis mycobacteria in urine, a bacterioscopic study is carried out with staining of smears from sediment according to Ziehl-Neelsen.

The detection of tuberculosis bacilli in urine is the most reliable sign of renal tuberculosis. When excluding prostate tuberculosis in men, the detection of tuberculosis bacilli in urine should be regarded as an indication of the presence of at least the smallest, "subclinical" foci of tuberculosis in the kidney. If a tuberculosis process in the kidneys is suspected, but a bacterioscopic examination is negative, a bacteriological examination of urine is necessary - its triple sowing for Mycobacterium tuberculosis.

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