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Sterility test: how to pass, what it shows
Last reviewed: 04.07.2025
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In modern medicine, there is an increasing need to study the sterility of biological fluids. For this purpose, a sterility analysis is performed. Almost any fluids are examined, including: blood, urine, breast milk. The purpose of the study is to identify bacterial microflora in fluids that should normally be sterile. Detection of bacteria in fluids indicates bacteremia, which indicates the generalization of the infectious process.
This analysis is especially important for people with HIV infection, since it makes it possible to detect the infection in the blood and prevent its further development. The appearance of bacteremia is a bad sign, since with HIV infection the immunity is reduced, and the body is not able to fight the infection.
In addition, those infected with AIDS are often carriers of Mycobacterium tuberculosis. Also, this method can not only identify the pathogen, but also determine the spectrum of its sensitivity to antibiotics. The importance of the study consists in the possibility of isolating one specific pathogen, identifying its sensitivity, and determining the degree of contamination.
Indications for the procedure sterility testing
Indications for the analysis are a general deterioration in well-being, increased fatigue, and the inability to normalizebody temperature for a long time. They take the test if there is severe lower back pain and the pain radiates to the kidney area. Disruption of normal urination is also an indication for the analysis. If an odor appears during urination, the urine becomes cloudy and sediment appears, it is also necessary to take the test.
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Preparation
It all depends on what kind of analysis needs to be done. The first condition that must be observed is the cleanliness of the genitals. At the same time, you should not use soap, since it significantly distorts laboratory indicators and can affect their reliability. It is necessary to prepare a sterile container in which urine will be collected. You can buy such a container at a pharmacy, it is sterile and ready for use. Or you can sterilize it.
Before taking the test, you must stop taking antibiotics and antifungal drugs, as the tests will be false negative. Before collecting the test, you must stop taking any medications.
The study requires an algorithm: first, a small amount of urine is released, then the main part is collected, and urination is finished. The urine should be morning urine, taken immediately after the person wakes up. The analysis requires approximately 50-100 ml of liquid. The lid is tightly closed, the analysis is delivered to the laboratory within 1-2 hours.
When taking other tests, the recommendations are almost the same. The main conditions are maintaining sterility, refusing to take antibiotics for 14-15 days, refusing to eat or drink for 4-5 hours before taking the test.
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Technique sterility testing
The main research method is bacteriological seeding. For this purpose, a nutrient medium is prepared in sterile conditions. At the first stage, a universal nutrient medium is used, for example, meat-peptone broth, agar medium. Primary seeding of biological material is performed. Then it is incubated in a thermostat at human body temperature.
Part of the material is subjected to a microscopic examination method, during which a smear is prepared, examined first under low magnification, then under high magnification. This will allow a preliminary conclusion to be made. It is possible to detect signs of an inflammatory process, the appearance of impurities, protein, sediment, which could indicate various inflammatory or infectious processes.
Incubation is carried out for several days (on average 3-5 days), after which the largest colonies are selected. They are transferred to selective nutrient media on Petri dishes. Some of the cultures are transferred to slants, incubated for several more days. After abundant growth is obtained, we isolate the colony, study its microscopic, biochemical, immunological properties.
The species and genus of the microorganism that is the causative agent of the disease are identified. After this, the concentration of bacterial cells is determined using a spectrophotometer or turbidity standard. If necessary, a study is conducted on antibiotic sensitivity, as well as on sensitivity to bacteriophages.
For this purpose, the disk diffusion analysis method or the decimal dilution method is used. The degree of bacterial growth inhibition is used to assess sensitivity to antibiotics, determine the rating of the most effective of them, and select the optimal concentration.
To confirm the diagnosis of bacteremia, multiple tests are used.
Blood test for sterility
The purpose of the study is to assess the sterility of the blood and identify bacteremia. Detection of such pathologies may indicate the development of a pathological and infectious process. The study is mainly aimed at detecting opportunistic, pathogenic microflora, fungi. Such clinically significant pathogens as staphylococcus, streptococcus, enterobacteria, and Candida fungi are considered quite dangerous.
This study is especially important for patients with HIV infection. It is used when there is a suspicion of generalization of the infectious process, development of purulent-septic processes. It is also used before prescribing antibacterial therapy to exclude incorrect prescriptions. It is performed on people with prolonged fever.
The essence of the method is to detect bacteria that penetrate from the vascular bed into the bloodstream. The fact is that with severe inflammation, bacteria from a nearby source of infection can penetrate into the blood. Then, with the bloodstream, bacteria can spread throughout the body, can penetrate into other organs and tissues, causing an inflammatory and infectious process there. The infection can spread throughout the body, like metastases in cancerous tumors. Complications include disturbances in the functioning of the heart and liver. This process can be prevented if the necessary measures are taken in a timely manner.
The analysis makes it possible to identify such diseases as meningitis, myocarditis, pyoderma, osteomyelitis, sepsis. The end result is the identification of the pathogen, its concentration. An effective antibacterial agent and its dosage are also selected.
The biological material for the study is venous blood. The collection is carried out in a laboratory, outpatient clinic, or medical center using standard methods. Sometimes, to stimulate the release of bacterial cells from the depot (spleen, liver), an adrenaline solution is administered beforehand. An average of 5-10 ml of blood is required, and is carried out using a standard method.
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Urine analysis for sterility
The purpose is to detect bacteria. Normally, urine is a sterile biological fluid. Bacterial microflora appears only when a disease develops. Usually, the need for such an analysis arises if a general urine analysis indicates the development of an inflammatory and infectious process. This is indicated by the presence of bacteria, epithelium, mucus, leukocytes, and erythrocytes in the urine.
When conducting and collecting material, it is important to maintain sterility. The end result is the detection of bacterial microflora, its quantitative and qualitative indicators, selection of an antibiotic, and the optimal dosage.
Urine test for sterility in a child
Indications for the analysis are suspected bacteremia and sepsis, in severe forms of inflammatory and infectious diseases. There are special urine collectors for infants. In this case, the ureter is installed in the morning; it cannot be installed in the evening. This is due to the fact that only the morning portion of urine must be used for the study. It is recommended to install it 2 hours before the child wakes up. Thanks to the modern design, it can be easily installed without waking the child.
The child must be washed in the morning. Only clean water is used, without any antiseptics, cosmetics, or soap. Dry the skin with disposable towels. After collecting the urine, there are 2 hours to deliver it to the laboratory. Otherwise, the results will be distorted, or the analysis will not be done at all. It takes quite a long time - 10-20 days. This is determined by the growth rate of microorganisms. Treatment usually begins after the test results are received.
Urine test for sterility in pregnant women
It is carried out when an infectious process develops, regardless of the period. It is also prescribed regardless of complaints and pathologies. The analysis is taken twice, since bacteremia often does not manifest itself in any way. It can cause complications during childbirth, contributes to infection
Breast milk sterility test
Breastfeeding is very important for a child, as it can provide him with strong immunity, reduces the risk of developing allergic reactions. But in some cases, for example, with bacteremia, milk can only harm the child, causing infection, up to sepsis. The study is necessarily carried out in the development of inflammatory and infectious processes in the mammary gland. This makes it possible to quickly identify the causative agent of the disease and select the appropriate treatment.
The purpose of milk sterility analysis is to identify pathogens of infectious diseases, microorganisms, the source of which is inside the body or in the external environment. The most dangerous are pathogenic and opportunistic forms of infection, as well as fungi. The type and genus of microorganisms are identified, as well as their quantitative indicators. Most often, staphylococci, streptococci, Candida fungi, and Klebsiella are found in breast milk.
Donated in medical centers, laboratories. On average, the analysis takes from 7 to 10 days. When collecting, it is necessary to take into account that the collection should be made from each mammary gland into a separate container. Before collecting, hands should be washed with soap, the mammary glands should be treated, hands and the alveolar zone should be treated with an alcohol solution. The last portion is used. An average of 10 ml of milk is required. During the collection, it is necessary to ensure that the hands do not touch the nipples.
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How long does it take to do a sterility test?
The sterility analysis is performed from 7 days to 1 month. It is determined by the growth rate of microorganisms, so it is not possible to speed it up. In some cases, it is possible to add growth factors, which will speed up the sterility analysis by several days.
Normal performance
The indicators are different for each type of analysis. Normally, many biological fluids should be sterile. In pathology, microorganisms are found in biological fluids. The severity of the infectious process depends on specific indicators. The unit of measurement is CFU/ml, i.e. the number of colony-forming units in 1 ml of fluid.
On average, there are also general indicators. Thus, indicators up to 1000 CFU/ml indicate an accidental entry of microflora into biological fluid. This is the so-called transient microflora, which does not require treatment. If the number of microorganisms fluctuates between 1000 and 10,000 CFU/ml, the analysis requires a repeat, since the result is questionable and can fluctuate depending on the impact of many external and internal factors. Indicators over 10,000 CFU/ml indicate the presence of an infectious process, requiring mandatory treatment. Usually, in such a case, antibiotics are required.
The device for analysis
To conduct the analysis, complex laboratory equipment is required. Thus, to conduct the primary seeding, micropipettes and dispensers, a centrifuge for separating biological fluids are required. To prepare nutrient media, a steam bath or a medium cooker (a special device for preparing artificial media) is used. To maintain optimal conditions and the required temperature, a thermostat is used. To ensure and maintain sterility, a dry-heat cabinet, an autoclave, and a desiccator are required.
Autoclaves are used to dispose of waste biological material. Gas burners or spirit lamps, fume hoods, and ultraviolet lamps are used to maintain sterility and prevent contamination. Various microscopes (light, phase-contrast, fluorescent, atomic force, and others) are used to evaluate the results.