Collection of biomaterial for laboratory research is a procedure that requires strict adherence to time frames and temperature conditions, especially when it comes to microbiological research. Any deviations from the schedule can lead to distorted results, since the intestinal microflora is a living system where bacteria continue to interact even outside the body. If you plan to take an analysis for dysbacteriosis, you need to prepare a sterile container in advance and familiarize yourself with the transportation rules.
The question of how long the collected material can be kept in the cold is one of the most common among patients. Laboratory diagnostics requires freshness of the sample, since some types of bacteria quickly die upon contact with oxygen or changes in temperature. The maximum permissible storage time for feces for dysbacteriosis in a household refrigerator is no more than 6 hours from the moment of defecation. Exceeding this period makes the analysis uninformative.
The ideal option is always to deliver the biomaterial to the laboratory within 1–2 hours after collection. However, the rhythm of life and the work schedule of medical institutions do not always allow this to be done instantly. In such cases, proper cooling becomes the only way to keep bacterial composition close to the natural state. It is important to understand that freezing is completely excluded, since ice crystals destroy the cell walls of microorganisms.
Why time is critical
The intestinal microflora is a complex ecosystem where anaerobic and aerobic bacteria are in dynamic equilibrium. After leaving the body, this balance is disrupted: some species begin to actively reproduce, others quickly die. This is why diagnosis of dysbacteriosis it is so sensitive to time delays. If the material stands at room temperature for several hours, the number of opportunistic organisms can artificially increase, and beneficial bifidobacteria can disappear.
The refrigeration chamber allows you to slow down the metabolic processes in bacteria, “preserving” their state at the time of collection. However, even at low temperatures, the processes of decomposition and fermentation do not stop completely. Long-term storage leads to a change in the pH of the environment, which is detrimental to many sensitive strains. Therefore, the phrase “I collected it last night, I’ll take it in the morning” is a fatal mistake for the accuracy of laboratory analysis.
It is worth noting that different groups of microorganisms have different resistance. For example, enterobacteriaceae are more tenacious than gentle anaerobes. If you violate the storage rules, the laboratory technician may see a picture that has nothing to do with the real state of your health. This will lead to an incorrect diagnosis and, as a result, to ineffective treatment.
⚠️ Attention: If more than 6 hours have passed since defecation, it is pointless to submit such material for dysbacteriosis. The result will be false and the money will be wasted. In this case, it is necessary to collect a new portion.
Optimal storage conditions for biomaterial
To ensure the safety of the sample, it is necessary to create conditions as close as possible to body temperature, but with a slower reaction. The main area for short-term placement of the container is the middle shelf of the refrigerator, where the temperature remains stable in the range from +2 to +4 degrees Celsius. Placement in the refrigerator door is unacceptable due to constant temperature changes when opening.
Sterility is the second key factor. The container must be tightly closed to prevent the entry of foreign microorganisms from the air of the refrigerator or from other products. Cross contamination can distort the picture of the study by adding bacteria to the sample that are not in the patient’s intestines. Use only special pharmacy containers with an airtight lid.
It is also important to consider the location of the container relative to the freezer. If you place the jar too close to the wall of the freezer, there is a risk of local freezing of the contents. Even partial crystallization of moisture will destroy the structure of bacteria. It is optimal to keep the container in the center of the shelf, perhaps additionally wrapping it in a clean napkin or placing it in a clean plastic bag.
Collection specifics for children and adults
The collection procedure for adults usually does not cause difficulties, but with children the situation is different. For babies who are not yet using the potty, the material is often collected from a diaper or diaper. In this case, it is important to collect feces from the surface without touching the absorbent layer of the diaper, since the gel filler can react with the sample and change its chemical composition If the child uses the potty, the container must first be thoroughly washed with soap, doused with boiling water and dried. The use of chemical disinfectants to treat the pot before collection is prohibited - residual chlorine or other agents can kill part of the microflora even before the analysis begins. For children, the same storage time frames apply as for adults: no more than 6 hours..
If a child goes to the potty, the container must first be thoroughly washed with soap, doused with boiling water and dried. The use of chemical disinfectants to treat the pot before collection is prohibited - residual chlorine or other agents can kill part of the microflora even before the analysis begins. For children, the same storage time frames apply as for adults: no more than 6 hours.
Particular attention should be paid to the consistency of the stool. Only formed or mushy stools are suitable for analysis for dysbacteriosis. Liquid feces (diarrhea) are more difficult to collect, and they quickly lose their properties due to the high moisture content, in which fermentation processes are more active. In such cases, the speed of delivery to the laboratory becomes even more critical.
What to do if the child pooped at night?
If the bowel movement occurred at night, collect the material in a sterile container, close tightly and place in the refrigerator. In the morning, immediately after waking up, take him to the laboratory. The main thing is to keep within the 6-hour interval.
Table of permissible storage periods
To systematize information about the permissible storage time of various types of biomaterial and conditions, it is convenient to use a summary table. It will help you quickly navigate in an emergency situation and understand whether your sample is suitable for clinical research.
| Type of analysis | Storage conditions | Maximum period | Risk of error |
|---|---|---|---|
| For dysbacteriosis | Refrigerator (+2...+4°C) | up to 6 hours | High |
| For occult blood | Refrigerator | up to 12 hours | Medium |
| Egg worm | Refrigerator | up to 24 hours | Low |
| For carbohydrates | Refrigerator | up to 4 hours | High |
As can be seen from the table, analysis for dysbacteriosis belongs to the category of the most demanding in terms of the freshness of the material. This is due to the need to grow bacterial cultures on nutrient media. Dead or altered bacteria simply will not grow in the Petri dish, which will be interpreted as their absence in the intestines.
⚠️ Attention: Do not freeze feces in the freezer! After defrosting, the structure of the bacteria will be disrupted, and the analysis will show a complete absence of microflora or a false positive result.
Rules for transportation to the laboratory
Even if you follow all the rules for storing at home, it is important to correctly deliver the container to its destination. During the warm season, the temperature difference between the refrigerator and the street can be significant. For transportation, it is recommended to use a thermal bag or a regular bag with a cold pack (or just a bottle of frozen water wrapped in a towel) to maintain a stable temperature.
You must have a referral for analysis and a passport with you. The laboratory technician will check the integrity of the container and the presence of markings. If the container is leaky, dirty on the outside or not labeled, the material may be refused acceptance. This is a standard quality control procedure aimed at eliminating identification errors.
Try not to shake or shake the container during transportation. Mechanical action can promote mixing of layers of feces, which, although less critical for bacteriology than for other tests, is still undesirable. Homogenization samples should only be carried out in the laboratory by a specialist.
☑️ Checklist before leaving
Frequent errors during preparation
One of the most common mistakes is collecting material after taking antibiotics or laxatives without consulting a doctor. Antibiotics inhibit the growth of bacteria, which makes analysis for dysbiosis pointless. Usually you need to wait 2 weeks after finishing the course of therapy. Laxatives accelerate the transit of contents, preventing the formation of normal microflora in the lower intestines.
Another mistake is collecting stool after an enema or X-ray examination with barium. Barium has bactericidal properties and will completely distort the result. Also, you should not collect material during menstruation in women, since blood entering the vaginal secretion can affect the growth of some cultures.
Do not try to “save” the material by collecting it in unsterile food jars (yogurt, mayonnaise). Even after thorough washing, microparticles of detergents or remnants of previous contents remain in them, which are harmful to bacteria. A sterile container is inexpensive, but guarantees the purity of the experiment.
Interpretation of results and retaking
Having received the form with the results in your hands, do not rush to make diagnoses yourself. The norm for intestinal microbiocenosis is a flexible concept and depends on age, diet and immune status. The laboratory produces indicators in colony-forming units (CFU), and a gastroenterologist should decipher them.
If the results are in doubt or do not correspond to the clinical picture, the doctor may prescribe a repeat test. In this case, the collection rules remain the same. Sometimes it is necessary to test feces three times with an interval of several days in order to get an average and most reliable picture of the state of the microflora.
Remember that dysbiosis is not an independent disease, but a consequence of some disturbances in the body. Therefore, even if the storage was perfect and the analysis was done correctly, it is important to look for the root cause of the changes, and not just restore the flora with probiotics.
Is it possible to store feces in the refrigerator for more than 6 hours if a preservative is added?
At home, using preservatives is impossible and dangerous. There are special transport media (for example, Cary-Blair), but they are used in hospitals and laboratories. For a routine test for dysbacteriosis, which is taken at a clinic, no preservatives are used, since the bacteria must be alive for inoculation.
Does the fact that the stool was collected the day before affect the analysis?
Yes, it does have a critical effect. Overnight (8-10 hours), even in the refrigerator, the composition of the microflora changes significantly. Aerobes multiply, anaerobes die. The result will show a sharp imbalance, which may not exist in reality. Such an analysis is considered a defect.
What to do if it is not possible to get to the laboratory in 6 hours?
In this case, you should look for laboratories with a more flexible appointment schedule or those that work until late in the evening. Some private clinics offer a service of calling a courier who will pick up the material immediately after collection. If this is not possible, you will have to get up early in the morning and collect the material just before leaving.