Urine analysis for bacterial culture
The content of the article:
- Bacteria in urine
- Indications for analysis
- Preparing for urine analysis for bacterial culture
- Rules for collecting material for analysis
- Analysis result
Urine analysis for bacterial culture (bacteriological examination) is used to detect bacteria in urine, select antibacterial drugs and control the treatment of infectious and inflammatory diseases of the pelvic organs.
Bacteria in urine
Infectious and inflammatory processes in the urinary tract are characterized by a recurrent course with a high likelihood of complications. Most often, the urethra and bladder are affected, often the infection spreads to the ureters and kidneys. The disappearance of clinical signs of an acute bacterial infection in the urinary tract often speaks not of recovery, but of the chronization of the process, that is, its transition into a sluggish chronic form. Inflammation and bacteriuria (bacteria in the urine) persist, which helps identify urine culture.
Bacterial culture of urine is performed on nutrient media, after which the growth of bacteria, their type, etc.
Normally, there are no microorganisms in the urinary tract, the only exception is the distal urethra, which is inhabited by microflora from the skin of the perineum (in women, also from the vulva).
95% of all pelvic inflammatory disease is caused by microorganisms. The causative agents of urinary tract infections are usually Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Citrobacter, Proteus mirabilis, Serratia. In addition, staphylococci (S. epidermidis, S. aureus, S. saprophyticus), streptococci (S. pyogenes), mycoplasma (Mycoplasma), etc. become infectious agents. In uncompensated diabetes mellitus, microscopic fungi of the genus Candida are often found in the urinary tract.
Urinary tract infections are promoted by pathologies in which the outflow of urine is impaired, as well as systemic diseases. In children, the elderly and debilitated patients, the infectious process often occurs in a latent form or has non-specific manifestations (indigestion, weight loss, etc.).
To determine the pathogen, a bacterial urine culture is performed. A referral for research is usually issued by a therapist, urologist, obstetrician-gynecologist. If necessary, the doctor will explain in detail what a urine culture test is, what this study shows, how to collect material, how much test is done. Only a specialist should decipher the result obtained.
Indications for analysis
Unlike clinical urinalysis, bacteriological analysis is not carried out for prophylactic purposes, but is prescribed if there are signs of a urinary tract infection. The reason for the appointment of a bacterial culture of urine may be the detection of bacteria or fungi during a general urine test. In addition, this study is usually prescribed for patients with recurrent cystitis, paranephritis, pyelonephritis, chronic urethritis, diabetes mellitus, as well as for monitoring the condition of HIV-infected patients, etc. Urine culture analysis refers to mandatory studies that are carried out by pregnant women, in 3– In 10% of cases, asymptomatic bacteriuria is determined.
Urine for bacteriological analysis is taken before the start or 7-14 days after the end of antibiotic therapy (control study), unless other conditions are indicated by the attending physician.
Preparing for urine analysis for bacterial culture
There are a number of rules for preparing for the delivery of urine for bacteriological research, the observance of which allows you to get the most reliable result.
A week before the analysis, it is recommended to exclude salty, spicy and fatty foods, as well as alcoholic beverages from the diet.
Women should not donate urine for bacterial culture during menstruation and for two more days after it ends, since menstrual flow, which is highly likely to get into the collected material, will affect the study result. It is also not recommended to use contraceptives or medications in the form of vaginal suppositories two days before the examination. Douching should not be done before taking material for analysis.
Rules for collecting material for analysis
Before collecting urine, a thorough toilet of the external genital organs is performed without the use of antibacterial soap. Men are advised to thoroughly rinse the penis and the fold of the foreskin before collecting material to prevent urine contamination. For the study, it is necessary to collect the average portion of the first morning urine (that is, the initial and last portions go down the toilet). Urine is collected in a special sterile disposable container, which is issued in the laboratory before analysis or purchased at the pharmacy. Some laboratories can purchase a preservative transport tube (usually boric acid). When collecting urine, do not touch the inner wall of the container.
Material for bacteriological examination in infants is collected using a urine collection bag, which can be purchased at a pharmacy, and then poured into a sterile container.
To collect urine for bacterial culture, you should not use glass jars, household plastic containers, since it is usually not possible to ensure the sterility of such containers at home. Also, do not use non-sterile disposable containers.
The material must be delivered to the laboratory no later than two hours after collection.
Analysis result
The main task of the analysis is to identify microorganisms in the urine and determine their etiological role. The type of infectious agent, the degree of bacteriuria, the detection of microorganisms in repeated studies, etc. are taken into account.
Bacterial inoculation of urine is performed on nutrient media using a bacteriological loop, swab or spatula. Normally, the growth of microorganisms is absent, signs of microbial growth indicate the presence of a bacterial infection in the urine, i.e., bacteriuria.
The degree of bacteriuria allows differential diagnosis of the infectious process from contamination of urine with normal microflora. So, bacteriuria of up to 10 3 microbial cells in 1 ml of urine usually indicates the absence of an infectious and inflammatory process and, as a rule, is determined in the case of contamination of urine, with bacteriuria of 10 4 the result is doubtful and there is a need for re-examination, 10 5 or more - infectious and inflammatory process.
Acute infections are characterized by a monoculture of bacteria, chronic infections - by bacterial associations
In order to control the ongoing therapy, the change in the degree of bacteriuria is assessed, its decrease indicates the effectiveness of the drugs used. However, when decoding the urine analysis for bacterial culture, it should be borne in mind that in a number of cases (during antibiotic therapy, low pH and / or specific gravity of urine, impaired passage of urine, etc.) a low degree of bacteriuria can also be determined in the presence of a pathological process. For this reason, the identification of infectious agents found in the urine is also of great importance (re-isolation of bacteria of the same species, as a rule, indicates the presence of infection).
Detection of monoculture or association of microorganisms in urine is of diagnostic value. In acute infectious and inflammatory processes, a monoculture is usually isolated against a background of high-grade bacteriuria, and in chronic ones - associations of microorganisms against a background of low-grade bacteriuria.
In addition to identifying an infectious agent, when conducting a urinalysis for bacterial culture, the sensitivity to antibiotics of isolated strains of microorganisms can be determined.
To make a diagnosis, not only urine culture data are usually used, but also other studies, and clinical signs of pathology are also taken into account.
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Anna Aksenova Medical journalist About the author
Education: 2004-2007 "First Kiev Medical College" specialty "Laboratory Diagnostics".
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