Why do urine cultures for flora: decoding of bacteriological research. Urine culture analysis for flora How to take a urine culture analysis for sensitivity

In urological practice, urinary tract infections are the most common bacterial diseases, the treatment and diagnosis of which has its own difficulties, most often associated with the atypical nature of the pathogen and its resistance to antibiotic therapy.

Therefore, according to modern medical recommendations, for the diagnosis and monitoring of the course of urinary tract infections in high-risk individuals, it is mandatory to conduct a urine culture. In this material, we will consider what a urine culture is, what this analysis shows and how to properly prepare for it.

Bacteriological culture (bacteriological culture or bacteriological examination of urine) for the presence of pathological microflora is a high-precision microbiological analysis that allows not only to isolate and identify the causative agent of urinary infection, but also to determine its exact concentration (degree of bacteriuria), as well as the degree of sensitivity to the most important groups of antibacterial agents.

The study allows:

1 Identify the causative agent of the infection;
2 Determine its diagnostic titer in 1 ml of urine;
3 Detect the presence of antibiotic resistance (resistance or sensitivity to antibiotics);
4 Monitor the decrease in the titer of the pathogen during therapy;
5 Choose the most effective antibacterial treatment drugs;
6 Monitor the prevalence of antibiotic-resistant strains of microorganisms in the population.

Indications for bacteriological examination of urine

The main goals of the analysis pursued by the attending physician when prescribing a urine culture are the diagnosis and monitoring of bacterial infections of the urinary tract, as well as determining the sensitivity of the pathogen to antibiotic therapy.

Sometimes bacteriological examination (bakposev) of urine is used as a screening for the prevention of inflammatory diseases of the urinary tract in high-risk individuals (pregnant women, the elderly, patients with diabetes mellitus). The main indication for the appointment of urine culture is the presence of symptoms of a urinary infection.

However, according to Russian urological recommendations, if a patient has an uncomplicated urinary infection, as well as in the absence of concomitant diseases, antibiotic therapy can be prescribed empirically, without prior identification of the pathogen. Empirical prescription of antibiotics can achieve a positive effect in about 75-80% of cases.

Unconditional indications for the study of urine for microflora are:

1 Urinary tract infections in pregnancy;
2 Suspicion of the presence of pyelonephritis in the patient;
3 All urinary tract infections in men;
4 Outbreaks of nosocomial urological infections;
5 Fever with prolonged catheterization of the bladder, as well as suspicion of a urological infection associated with medical manipulation (cystoscopy, catheterization);
6 Fever above 38 C for no apparent reason in children under 3 years of age;
7 Recurrent urinary infections, failure of previous empiric antimicrobial therapy;
8 Complicated urinary infections over the age of 65;
9 The appearance of symptoms of a urological infection in people with impaired immune status, chronic kidney disease, diabetes mellitus, congenital anomalies in the structure of the kidneys and ureters, after kidney transplantation;
10 Reception by patients during the previous three months of antibacterial drugs, which theoretically could lead to the formation of resistant forms of pathogens.

1 Women during pregnancy, after 14 weeks, even in the absence of any symptoms of pathology, which reduces the risk of developing pyelonephritis in pregnant women;
2 Patients with a planned surgical intervention on the organs of the urinary system;
3 Patients with a kidney transplant during the first two months after surgery, and then with any deterioration in the functioning of the transplanted organ.

2. Rules for collecting material

How to properly pass urine culture during pregnancy, in adults and children, we will consider further. To ensure the accuracy of laboratory diagnosis of urological infection, it is important to comply with all stages of diagnosis, including its preanalytical part - the collection of urine samples and their delivery.

It is the need to determine the exact amount of bacterial agents in the test sample that places special demands on sample collection.

When conducting a study in a hospital, the nursing staff of the hospital is responsible for preparing the patient, collecting the material and transporting it to the laboratory. For such cases, laboratories have written instructions that govern all diagnostic steps.

When examined on an outpatient basis, the patient collects urine on his own, without the supervision of a medical worker. In connection with the foregoing, it is necessary to carefully instruct the patient in the technique of performing self-collection of the test material, in order to avoid a false result of the analysis.

1 Urine must be collected in a sterile disposable container specially designed for this, which can be purchased at the pharmacy chain. It is not allowed to collect urine in non-sterile, previously used containers, jars or bottles;
2 If possible, urine sampling should be carried out before the start of taking antibacterial drugs or in the intervals between drug courses, to avoid distortion of the information received;
3 The most reliable study of the average morning portion of urine - after a night's sleep and before breakfast;
4 In the evening, on the eve of urine collection, it is recommended, if possible, to refrain from taking diuretics, since when they are taken, urine is diluted and the total number of bacteria in one milliliter decreases;
5 To collect urine from infants, special children's urinals with a hypoallergenic adhesive should be used, the collected sample is subsequently poured into a urine collection container, labeled and transported to the laboratory.

Figure 1 - Sterile containers for collecting urine for analysis (without a spatula)

3. The main stages of self-collection of urine

The urine collection procedure described below applies to all adults, including pregnant women. The optimal volume of urine for microbiological analysis is approximately 10-20 ml, and the minimum should not be less than 1 ml.

The stages of self-collection of the material under study can be represented as follows:

1 Wash hands thoroughly with soapy water, dry them with a clean (preferably disposable) towel;
2 Make a toilet of the external genitalia using warm soapy water, without the use of skin antiseptics, dry the inguinal area with a clean disposable cloth;
3 Open a pre-prepared sterile container, avoiding touching its inner surfaces with your fingers;
4 Release the first portion of urine, stop urination;
5 Collect the next (middle) portion in a prepared sterile container, without touching the skin in the inguinal region with the container;
6 Finish urinating into the toilet;
7 Tightly close the lid of the filled container, sign, attach the direction for analysis to the container with a thin rubber band, and deliver it to the laboratory.

It is unacceptable to use urine from a bedpan and urine from women during menstruation for microbiological research.

How to collect urine for bacterial culture in a child?

1 Give the child a drink of warm water or other liquid (you can give the baby a breast);
2 Wash hands with soapy water, dry with a clean towel;
3 Make a toilet of the external genital organs of the child;
4 If possible, make a sample of the middle portion of urine, seating the child on the lap of an assistant. If it is impossible to take the middle portion, you can use a specially designed children's urinal, which should be checked at least every 10 minutes.
5 Do not use urine from a pot for analysis.

Figure 2 - Collection of urine from an infant in a sterile urinal

4. Rules for the delivery of material to the laboratory

The conditions of delivery of the urine sample to the laboratory have a direct impact on the accuracy of the bacteriological examination, since they can both reduce viability and stimulate the growth of bacteria in the presented portion of urine.

The sample should be delivered to the laboratory no later than two hours after collection. The optimal time for sowing urine samples is less than 30 minutes after urination, however, due to the difficulty of implementing this condition, this period in many laboratories is regulated up to 1-2 hours.

If it is impossible to carry out delivery within the specified period, it is allowed to store the material at a temperature not exceeding +40C within a day from the moment of collection. Freezing a urine sample is prohibited - this leads to the death of some types of microorganisms.

To improve the quality of the study, as well as to ensure longer storage, the use of special stabilizers, for example, 1% boric acid, is allowed. However, the addition of such preservatives is permissible only to a strictly permitted extent.

In this regard, when conducting a bacteriological study of urine, it is advisable to use commercial transport systems (special tubes), in which a certain concentration of preservative is achieved by adding a certain amount of urine.

In the presence of special test systems, it is possible to carry out express bacterial culture without leaving the patient's bedside (test strips "Diaslide", "Dipstrik"), however, in Russia this is not common due to the high cost of equipment.

All urine samples received by the laboratory must be marked by the laboratory assistant in any way possible, allowing you to accurately identify one sample from another.

Not accepted for research:

1 Urine samples without labeling and referral;
2 Samples without indication of date, time and method of collection;
3 Stored for more than 24 hours from delivery;
4 When the integrity of the collection container is broken;
5 Spilled and exposed samples.

5. Technique

Russian laboratories perform a urine test for microflora in accordance with the order of the Ministry of Health No. 535 dated April 22, 1985 "ON UNIFICATION OF MICROBIOLOGICAL (BACTERIOLOGICAL) RESEARCH METHODS USED IN CLINICAL AND DIAGNOSTIC LABORATORIES OF THERAPEUTIC INSTITUTIONS"

Over the past few years, the order has been repeatedly supplemented and updated.

A bacteriologist and a laboratory assistant (medical assistant-laboratory assistant) participate in the bacteriological culture. The duties of the doctor include control of the technology of the study and the direct implementation of all the necessary stages of diagnosis.

The laboratory assistant is responsible for receiving incoming urine samples, preparing accompanying documents for them, preparing the necessary diagnostic media and reagents, cultivating the culture, quantitatively counting the grown bacterial colonies, destroying consumables and sample residues.

Several types of nutrient media are used for sowing:

1 Universal (blood agar, CLED) - supporting the growth of both gram-positive and gram-negative microorganisms;
2 Differential diagnostic (chromogenic) - used to differentiate uropathogens, changing color upon contact with their metabolic products;
3 Selective (Columbian agar, Endo agar, McConkey) - allow you to separately grow gram-positive and gram-negative pathogens.

The acquisition of nutrient media for the cultivation of pathogens occurs in finished form or in the form of specialized dry mixes for self-preparation. For dry mixes, an instruction is necessarily attached that precisely regulates all stages of preparation.

To obtain the result of urine bakposev by a non-sector method, a certain volume of the test material is applied to a Petri dish filled with a non-selective medium (in this case, exactly 1 μl of urine). Then a special microbiological loop is immersed into the test sample, tipped to the appropriate volume.

The material is spread across the surface in the central region in a series of straight lines and then in horizontal strokes perpendicular to them.

Figure 3 - Urine culture, application of material to a nutrient medium in a Petri dish

When using the method of sector crops, the Petri dish is pre-divided into 4 equal sectors, indicated by letters of the alphabet. A sterile loop is used to culture urine in the amount of 0.005 ml, alternately in four sectors. When moving to the next sector, the loop is pre-burned.

Urine cultures on non-selective media allow for quantitative cultures, while selective media are used to obtain isolated colonies and the primary determination of the microorganism, so urine is not evenly applied to them.

Petri dishes are in a thermostat at a temperature of 35-37 for 18-24 hours, after which the result is calculated. In some cases (weak growth of flora, inconsistency of the result with the clinical picture, suspicion of the presence of fungi, etc.), incubation can be extended up to 2 days.

When bacterial growth is detected, using special tables, all types of grown colonies are recorded, and their possible pathogenicity is also assessed.

If probable uropathogens are detected, they are further identified by studying cultural, biochemical, tinctorial and agglutinative properties, and the degree of their sensitivity to antimicrobial drugs is also determined.

6. Determination of antibacterial sensitivity

Antibiotic susceptibility testing for uropathogens is performed using one of the three methods recommended by the European Committee on Antibiotic Resistance:

1 Disk method - a suspension of bacteria of a predetermined density is applied to the agar surface in a Petri dish, then disks containing a certain concentration of antibiotic are placed on top, which leads to the appearance of a zone of inhibition of bacterial growth, the diameter of which is used to judge the sensitivity of the microorganism and determine the minimum inhibitory concentration of the drug;
2 Gradient-diffuse E-test - the method is similar to the disc, but instead of antibacterial discs, E-test strips are used, containing an antibiotic concentration gradient from minimum to maximum. In this case, the minimum inhibitory concentration of the drug is also determined;
3 By the method of serial dilutions - the antibiotic is diluted in several known concentrations, after which it is introduced into the agar for the cultivation of bacteria. The degree of suppression of bacterial growth can also be used to judge the presence or absence of sensitivity to the antibiotic.

7. Interpretation of results

When deciphering the result of urine culture, the severity of the clinical manifestations of the urological infection, compliance with the method of sampling the material, rules for transporting and storing samples must be taken into account.

All types of urological infections can be divided into mono- and mixed, occurring with the release of up to two types of pathogens.

If three or more pathogens are found in the test material, the situation is considered as a sign of accidental contamination (contamination) of the urine sample. In this case, the study is recommended to be repeated in compliance with all stages of sampling and diagnosis.

Currently, all bacteria found in the urinary tract are usually divided into three groups, which affects their minimally significant diagnostic titer (when inoculated with 1 µl):

Primary pathogens (E. coli, salmonella, mycobacteria, leptospira). These microorganisms are obligate pathogens, their minimally significant diagnostic titer is more than 10x3 CFU/ml;
Secondary pathogens (enterobacteria, Klebsiella, Pseudomonas aeruginosa, Staphylococcus aureus, Haemophilus influenzae).

These pathogens are pathogenic only under certain conditions - with weakened immunity, after invasive medical procedures, with concomitant chronic conditions more, their minimum diagnostic titer is 10x4 CFU / ml;

Doubtful pathogens (coagulase-negative staphylococci, streptococcus agalactia, acinetobacter, Pseudomonas spp, their minimum diagnostic concentration is more than 10x5 CFU / ml.

The isolation of representatives of the normal microflora, such as diphtheroids, gardnerella, alpha-hemolytic streptococci, is not diagnostically significant.

8. Causes of false results

One of the most significant reasons for the appearance of false results of bacteriological analysis of urine is non-compliance with standardized research technology, in particular:

1 Increasing the inoculum dose of the test material;
2 Non-compliance with the duration of the preanalytical period for storing urine;
3 Violation of the norms of urine collection;
4 Lack of hygiene of the external genitalia before urine collection;
5 Collection of urine in unsuitable containers;
6 Violation of the temperature regime of storage and transportation;
7 Conducting research during antibiotic therapy or during menstruation in women;
8 Non-compliance with the exposure time of the material in the thermostat.

Urinalysis for flora: how and why to take

Sowing urine on the flora is performed in order to identify pathogenic bacteria, and in the future to find the most effective methods of dealing with them - certain antibacterial agents. Usually, a urine test for flora is prescribed when treatment fails, with kidney disease, diabetes, HIV, pregnancy, that is, when the risk to the body is especially high. With it, cystitis, urethritis, pyelonephritis are easily diagnosed.

How to take a urine culture for flora with the determination of sensitivity to antibiotics, what are the collection rules? Morning urine is needed, it is collected in a clean plastic container (sold in pharmacies). First you need to wash the genitals with water, but without using any detergents. It is necessary to collect an average portion of urine. The same rule must be observed when a referral is given for urinalysis according to Nechiporenko, which is also very often prescribed. You need to deliver the container to the laboratory within a maximum of 6 hours, but the sooner the better. In this case, the material is stored in a cold place. As for the volume of biomaterial, 5 grams is enough. This is quite a bit, if we take the Zimnitsky urinalysis as a comparison, when the entire daily volume is collected.

Normally, a laboratory assistant can detect various microorganisms in the urine. These are staphylococcus, diphtheroids, streptococci. But their number is very important. Bacteria should not be more than 105 CFU / ml, if the values are large - this means an acute inflammatory process. The disadvantage of this type of examination is the duration of this process, the results of urine culture for flora are usually ready only after one week. But treatment is most often required to appoint earlier. Reliability can be affected by the medications taken, mainly antibiotics, diuretics, obstructed urination, irregularities in the collection of biomaterial, and the experience of the laboratory technician.

At the first visit to the urologist, the doctor usually prescribes a general urinalysis, its "composition" is already known within a day. If there are a lot of erythrocytes, leukocytes, cylinders - this means inflammation. Urine culture for flora and sensitivity to antibiotics has a clarifying value. With the help of it, antibiotic therapy is corrected. Well, what will it give, whether the infection will pass, can be judged 2 weeks after the end of treatment.

Bacteriological urine culture (bacteriological culture, flora culture, etc.) is one of the varieties of laboratory urine testing. Unlike the general analysis of urine, the analysis of urine for flora is a rather complex, but at the same time highly informative, study.

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And if a standard urine test is prescribed every time you seek medical help, urine culture for flora has strict indications for conducting. It is also worth considering the fact that this study must be carefully prepared, because in this case, sterility is important when collecting urine. Bacteriological culture is prescribed for men and women both as a preventive study and to clarify existing diagnoses.

The main task of such a study is to identify harmful bacteria in the patient's urinary system. A tank analysis is prescribed to determine the presence of microflora that provokes the appearance of inflammatory processes and the development of infections in the body. Also bakposev shows colonies of certain types of bacteria, which allows us to draw conclusions about the general state of health of the genitourinary system and the whole organism as a whole.

But after all, urine is a product of human metabolism, a kind of "trash can", in which all substances are concentrated that, for one reason or another, are not demanded by the body. This liquid, by definition, cannot be sterile, which means that it is overpopulated with bacteria. How to study the state of health in such conditions?

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A urinalysis for culture shows whether the number of bacteria does not exceed the permissible limits and whether there are any conditionally harmful microorganisms that can cause serious damage to the patient's health.

Urine usually contains streptococci, staphylococci and diphtheroids. They are considered dangerous, but only in large quantities. And if their number exceeds the permissible norm, then infectious processes develop in the body.

In what cases is it assigned

Not suitable for every patient. If a referral for a general analysis of urine can be obtained from any specialist, then a tank analysis for sterility is prescribed by urologists or gynecologists. Usually a tank study is prescribed if:

there is a possibility of developing an infectious disease;
control of ongoing therapeutic therapy is required;
it is necessary to confirm the preliminary diagnosis;
there was a relapse of the disease;
a woman is preparing to become a mother;
the patient suffers from diabetes;
it is required to establish sensitivity to antibiotic drugs.

Most often, planting on the flora is necessary in order to establish the presence of inflammation and diseases of the bladder and urinary tract.

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The results of this analysis will depend on the treatment of the patient. Also, this study is carried out as an analysis for sensitivity to antibiotics, that is, in the course of laboratory diagnostics, it becomes clear whether the bacteria are resistant to a particular drug and whether it should be prescribed for treatment. Sometimes it is done in the middle of medical therapy if the patient is not getting better and his health is deteriorating. From this we can conclude that the bacteria are resistant to the antibiotic chosen at the beginning of treatment, and it is better to replace the medicine.

Sowing on the flora is mandatory for pregnant women, it must be given to patients suffering from endocrine diseases (diabetes mellitus) for general health monitoring during an annual preventive examination, and also if any disease has caused a relapse.

Urine culture during pregnancy is prescribed to all women to monitor the health of the genitourinary system. If the pregnancy proceeds without complications and the expectant mother does not suffer from kidney and bladder ailments, urine culture during pregnancy will need to be passed before registering and before going to the maternity hospital, at 35-36 weeks.

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If a protein is found in the general urine test or the patient complains of back pain, it will be necessary to undergo such a study again. Also, this study can be prescribed monthly for women suffering from chronic kidney disease, which they must inform their doctor when registering.

The advantage of the sterility analysis tank is the high accuracy of its results and accessibility to all segments of the population. But in order to make a diagnosis based on the diagnostic data and choose drug therapy, you need to carefully prepare for the study, otherwise it does not make sense.

How to prepare for the study

If urine is collected without meeting the requirements of the microflora study, the results will be incorrect, and this will lead to the appointment of the wrong treatment. Therefore, before taking a bacanalysis, you need to carefully study the information about the collection of urine.

First of all, you will need to purchase a sterile container for collecting urine. In the pharmacy there are containers with a lid, designed specifically for collecting urine.

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But in the laboratory, they usually give out their own container for collecting biomaterial, disinfected, dried and closed in accordance with the conditions of the laboratory. To purchase a container at a pharmacy or take it in a laboratory - the doctor who writes out a referral for a tank study will tell.

Before you start collecting urine, you need to prepare a towel for hygiene procedures. To do this, a clean towel is carefully ironed on both sides and folded in half. In this form, they bring it to the bathroom.

Next, you need to thoroughly wash your hands and genitals. It is forbidden to use cosmetics for washing; laundry soap is best in this case. Next, you need to wipe the genitals with a prepared towel, unfolding it (with the inside). Women are advised to cover the entrance to the vagina with a sterile cotton swab to prevent bacteria from the genitals from entering the urine.

Next, you need to open the prepared container without touching the inside of the lid and container. The first stream of urine is drained, because it helps to flush the urinary tract, and the middle one is carefully collected. The container is closed with a lid and taken to the laboratory.

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Before donating, it is better to refrain from sexual intercourse, excessive physical exertion and taking medications, if they are not vital medicines. It is also advisable to avoid eating foods that can color the urine and thereby distort the results of the study.

For the analysis tank, the biomaterial should be collected immediately before being sent to the laboratory. For the study tank, the morning portion of urine is needed, which contains the highest concentration of bacteria. Collecting urine in the evening, and then storing it in the refrigerator in this case is strictly prohibited. The storage period of the biomaterial collected for analysis should not exceed two hours. It is allowed to store urine in the refrigerator for no more than six hours if the trip to the laboratory is scheduled for the afternoon. If all the requirements for urine collection are met, the results of the tank analysis will be absolutely accurate.

Another question - how much urine does bakposev require? As with the general analysis, it is better to bring 50 to 70 ml of urine to the laboratory. But there are modern laboratories that require up to 10 ml.

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Therefore, this information should be clarified with the attending physician or in the laboratory itself.

What the results will tell

Results are prepared within 10-14 days. This time is necessary in order to grow a colony of bacteria, and then study them. Decoding usually consists of two forms: directly data on the presence of certain bacteria and an antibiogram, i.e. information on the sensitivity of microflora to antibiotics.

The result sheet includes information about the detected microorganisms, which are indicated in the CFU. The higher the CFU, the greater the concentration of certain bacteria in one ml of liquid. Usually, CFUs have upper and lower limits, the excess of which indicates that an inflammatory process is developing in the body.

The antibiogram includes information about all types of bacteria that are present in human urine. Opposite each representative of the pathogenic microflora is information about whether this particular species was found in the material under study. It is also mandatory to contain information about which types of antibiotics they have sensitivity to.

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Thanks to the first decoding point, the attending physician will be able to determine whether the patient has diseases, the second will help identify the causative agent of the disease and make the correct diagnosis. Thanks to the third point of decoding, the specialist will be able to choose drugs for therapeutic therapy as correctly as possible.

Since urine is not sterile, bacteria are present within acceptable limits. When deciphering the received data, the doctor first of all studies their number. If the total number of microorganisms does not exceed 1000 cfu / ml, it can be said with confidence that the patient is healthy. Indications exceeding 100,000 CFU / ml indicate the development of an infectious disease and require appropriate treatment. Intermediate data require re-testing. Usually this is evidence of non-compliance with the requirements for the collection of biomaterial, less often - information about the onset of the inflammatory process.

Urinalysis for culture is of great importance in the effective diagnosis of diseases of the kidneys and urinary system. The urinary system is, at first glance, a fairly simple process: urine is formed in the kidneys (this is a type of excrement, a waste product of animals and humans), which then enters the bladder and is excreted from the body through the urethra. This process is so commonplace for a person that the latter, up to a certain point, does not attach any importance to it. The value increases only when this process fails (with kidney disease), and then the person turns to all kinds of medical research.

UAM (or also called clinical urinalysis) is a laboratory test that allows you to evaluate the physical and chemical characteristics of urine and sediment microscopy. Physical characteristics include the amount of urine, its color, transparency, reaction (pH), specific gravity (relative density). Chemical characteristics include protein, glucose, ketone bodies, bile pigments. Well, sediment microscopy is the amount of hemoglobin, erythrocytes, leukocytes, epithelial cells and cylinders. Diagnoses after this study can be varied, for example, leukocyte esterase. If the test is positive, then this means the presence of leukocytes in this type of excrement. Otherwise, leukocyte esterase casts doubt on the infection in the urine and suggests the need for other types of research.

This analysis is one of the most used (they begin to identify a particular disease most often from it), which helps to detect abnormalities in the work of both the urinary system and the kidneys.

Urinalysis according to Nechiporenko (the idea of this study belongs to the Soviet doctor A.Z. Nechiporenko) is a laboratory study that consists in determining the content of leukocytes, erythrocytes and cylinders in 1 ml of urine. This type of research has become widespread due to its relative simplicity and wide information content. The purpose of this study is to identify a hidden inflammatory process in the urinary system or kidney dysfunction, and, as a rule, it is carried out when abnormalities in the OAM are detected. The following proportions are considered normal limits:

Leukocytes - up to 2000 (in men), up to 4000 (in women).
Erythrocytes - up to 1000.
Cylinders - up to 20.

A urine culture is a laboratory test that detects the presence of microorganisms in the urine. The main task of the analysis (urine culture for sterility) is to prove the etiological (causal) role of microorganisms in the development diseases (their type, degree of bacteriuria (the presence of bacteria in the urine), as well as the frequency of bacterial isolation). In a healthy person, this species is sterile, that is, it does not contain any bacteria, otherwise this indicates the presence of an infection in the urinary system. Urine culture for flora is prescribed after the presence of deviations in OAM and urinalysis according to Nechiporenko.

These symptoms occur in people prone to the following diseases: acute and chronic cystitis, urethritis, pyelonephritis, as well as diabetes and immunodeficiency.

Deciphering the analysis of urine culture for microflora

The result of the study is indicated in the presence or absence of bacterial growth, the degree of urine for bacteriuria, expressed in CFU / ml, the name of the pathogen, sensitivity to antimicrobial drugs (determined with bacteriuria in a titer of 10 * 4 cfu / ml). So, when analyzing urine for a seeding tank, the concentration (number) of microorganisms in one volume unit of the biomaterial is set on colony-forming units (CFU).

A CFU is a single living microbial cell (or group of cells) that causes the growth of a visible microbial colony. If the detected number of bacteria in the urine is up to 1000 CFU / ml, then this means that the bacteria got there by chance, for example, from the external genitalia, which does not require treatment.

But if the number of microbes is equal to or exceeds 100,000 CFU / ml, then in this case there can be no talk of any bacteria that accidentally got in: this is an infection, and you need to contact a specialist for treatment.

With an intermediate result of 10-1000 CFU / ml, the analysis is considered doubtful, and it must be retaken. But, in spite of everything, do not try to decipher this or that analysis on your own (decoding by a non-specialist leads to ineffective treatment). Ask your doctor directly for this.

How to take a bacteriological analysis: rules for passing

Rule 1. Biomaterial (urine), as a rule, is collected in the morning after sleep. But there are also individual emergency cases in which the collection of material for research is collected 2-3 hours after the last urination.

Rule. Immediately before collecting urine, wash your hands and genitals. This measure is necessary to prevent false microbes from entering the biomaterial, which can lead to a distortion of the final result of the analysis.

Rule 3. Excrement must be collected in a special and, very importantly, sterile container (they can be purchased at pharmacies). In addition, it is necessary to collect exactly the middle portion of urine, i.e., the first and last drops should not fall into the container. This is necessary so that the bacteria in the urine test are concentrated in the maximum amount (if, of course, they are present in it).

After direct collection of urine, the analysis is delivered to the laboratory, where there are various nutrient media, on which a certain amount of material is applied. Observing certain favorable conditions for each type of bacteria, their colonies are grown. Based on these data, the result of the analysis of the microbe that caused the disease is made. To determine the sensitivity of bacteria to antibiotics, several such drugs are applied to their colonies in order to have some choice in the selection of a drug to fight the disease. Urine analysis for culture tank is prepared from 1 to 10 days (depending on the type of bacteria).

Only a little over 70 years have passed since the discovery by A. Fleming of penicillin, which was a revolutionary drug in the fight against various infections.

Today we have to observe the rapid growth of chemical and pharmacological activities to create new and new classes of antibiotics. There are already more than 10 of them, in each class there is more than one representative.

The problem has 2 aspects. First, microorganisms turned out to be “smarter” than scientists thought they were. They learned not only to resist the action of antibiotics, but also to build them into their metabolism. Secondly, people themselves, believing in the miraculous effect of antibiotics, began to use them not quite correctly - to disrupt the course of administration, to take without indications, to experiment with doses, to start taking them without consulting a doctor. By sensitizing the body with the wrong medication, a person contributed to the fact that forms of microorganisms that are absolutely resistant to most antibiotics appeared.

In order not to experiment with all 10 classes of antibiotics (beta-lactam penicillins, cephalosporins, macrolides, tetracyclines, aminoglycosides, lincosamides, carbapenems, polymyxins, glycopeptides, chloramphenicol), the bacteriological method began to be used in laboratory practice with the isolation of the pathogen and the establishment of its sensitivity to antibiotics.

The choice of material for sowing can be varied - bile, sputum, discharge from the ears, discharge from the genital tract, urine.

This article discusses - urine tests for flora and sensitivity to antibiotics.

No special preparation is required. The day before, the patient is explained how to take a urine culture tank. You should prepare gloves, a sterile jar for analysis.

Collection

For research, an average portion of morning urine is taken.

If it was not possible to pass the test in the morning, then you can take it at another time, but it is important to comply with the condition that at least 2-3 hours have passed after the previous urination.

It is strictly forbidden to open a sterile jar until the material is taken!

Why is it necessary to maintain sterility when collecting material? Urine in the bladder is normally sterile. But in the urethra, especially in the lower third, you can find a variety of flora. The external genitalia are also not sterile. With improper sampling, microbes from the urethra and genital organs can accidentally get into a sterile jar and distort the result.

Urinalysis is given after the hygienic toilet of the external genitalia. The use of antiseptic is prohibited. Treatment must be carried out with clean water.

The first portion of urine is released into the toilet, then the urine of the middle portion is released into the newly opened jar, it closes, urination ends in the toilet. The volume of the average portion is approximately 5-10 ml. During urine collection, contact of the genitals with the jar is unacceptable.

A sterile jar of urine should be delivered to the laboratory as soon as possible. Keeping it for 2 hours at room temperature leads to infection of the urine. Storage in the refrigerator during the day is allowed (in case of impossibility of immediate delivery).

Marking

Before delivering the jar to the laboratory, it must be signed. In addition to the surname and initials, the bank must indicate:

presumptive diagnosis;
date and time of taking the material;
sampling method;
information about previous antibiotic therapy about taking diuretics.

The sampling of material can be carried out through a catheter, but only if it is necessary to differentiate between inflammation in the bladder and in the kidneys.

The most reliable result can be obtained by sampling urine by suprapubic puncture of the bladder, which completely eliminates associated infection in the urethra, but it is rarely resorted to.

If the patient has a permanent catheter, then after clamping it and treating it with alcohol, a puncture is made and the contents are drawn into a syringe, then released into a sterile container.

A feature of confirming tuberculosis of the urinary tract is a three-time test daily.

Urine culture for flora and sensitivity to antibiotics

Distinguish qualitative and quantitative analysis of colonies grown after sowing. Qualitative analysis does not make it possible to distinguish the grown flora - it is from the bladder or from the urethra. Quantitative analysis involves counting grown colonies.

To carry out the calculation, it is imperative to follow the technique of sowing urine on the flora. Nutrients used:

nutrient agar;
5% blood agar;
sugar broth.

When working, the following methods are used:

sector crops with a platinum loop;
accelerated method.

Only 0.1 ml of urine is inoculated.

With sector sowing, the material is placed for a day in a thermostat at a temperature of 37 degrees. As a result, it is possible to isolate the pathogen in its pure form.

The accelerated method makes it possible to obtain a preliminary result in a day, the final one on day 4-5.

After removal from the thermostat, the number of colony-forming units (CFU) is counted and recalculated for 1 ml of urine.

Antibiogram

Urine tests for antibiotics, or more precisely for sensitivity to them, are performed in 2 versions.
In the initial study, a set of standard, widely used drugs is taken. This is a simple antibiogram.

Extended is necessary for:

extraordinary cases;
if the patient has already received many antibiotics;
if an additional course is needed;
when choosing an oral drug.

The doctor in the referral can indicate to which specific drugs he wants to test the sensitivity.
The disk-diffusion method is used to assess the effect of an antibiotic. Its essence is as follows.

When sowing a pure culture of the pathogen, cardboard disks impregnated with antibiotic solutions are simultaneously superimposed on it. Two processes - growth and inhibition - go on simultaneously. At the same time, it is clearly visible which effect of which drug prevents growth most actively, and which one does not have a significant effect.

How to evaluate the result?

When interpreting the results of the analysis, many factors should be taken into account. The following indicators matter:

degree of bacteriuria;
type of culture;
repeatability of sowing during repeated surveys;
isolated monoculture or in association with others.

Degree of bacteriuria:

Within 10-10 2 it has no diagnostic value, there was a passing infection during the sampling of the material.
10 3 CFU in 1 ml indicates the absence of an inflammatory process.
10 4 - the result is doubtful, the analysis must be repeated.
10 5 confirms the inflammatory process.

The type of isolated flora also suggests whether there is an inflammatory process. Diphtheroids, lactobacilli, gram + sticks most likely speak of associated flora from the external genital organs.

The infectious process is evidenced by the fact that with several crops, the same species is determined in the same degree of bacterial contamination.

Monoculture is usually accompanied by a high degree of bacteriuria and emphasizes the presence of an inflammatory process.

What influences the result?

First of all, the result is influenced by the correct observance of the technique of urine sampling.
Lack of instructions in the direction of taking antibiotics.
Violation of the terms of sending the material to the laboratory.

A false-negative result can occur under the following circumstances: the patient is taking antibiotics, has poor urine flow, urine specific gravity is low, pH is less than 5. The degree of bacteriuria will be low. In such cases, the interpretation of the result should be carried out taking into account the complaints and clinical symptoms of the patient.

There are many tests and studies to differentiate pathogens from each other.

The absence of bacteriuria in a single examination does not exclude the presence of an inflammatory process.