Collecting biomaterial for laboratory research is a process that requires strict adherence to time frames and temperature conditions. This is especially true for analysis on dysbacteriosis, where the composition of the intestinal microflora is a key indicator. Any delay or violation of transportation conditions can lead to the death of anaerobic bacteria, which will distort the clinical picture and lead to an erroneous diagnosis.
Many patients mistakenly believe that the refrigerator is a universal place for storing any biological samples indefinitely. This is a dangerous misconception. Anaerobic microorganisms, inhabiting the large intestine, are extremely sensitive to oxygen and temperature changes. Even inside the refrigeration chamber at a temperature of +4...+8°C, the vital processes of bacteria do not stop completely, but only slow down, which over time changes the ratio of different groups of microbes.
In this article we will analyze in detail how long it is allowed to keep a container with biomaterial in the cold, what nuances exist for different categories of patients and how to properly organize the collection so that the result The research was as reliable as possible. Understanding these processes will help you avoid repeated tests and wasting time and money.
The influence of temperature on the viability of bacteria
Temperature is a critical factor determining the quality of a biomaterial. At room temperature, bacteria begin to actively multiply, and after 2-3 hours the composition of the microflora becomes irrelevant. The refrigerator allows you to slow down this process, but does not stop it completely. That is why there is a strict limitation on storage time.
The optimal temperature for short-term storage is considered to be the range from +4 to +8 degrees Celsius. In such conditions enterobacteria other representatives of the microflora retain their viability, but do not have time to significantly change their numbers. However, even under these conditions, gradual degradation of the most sensitive strains begins.
⚠️ Attention: Freezing biomaterial for analysis for dysbiosis is strictly prohibited! Ice crystals destroy the cell walls of bacteria, making the sample unsuitable for research.
It is important to understand that different groups of bacteria react to cold differently. If opportunistic flora can survive the night in the refrigerator, then obligate anaerobes (for example, bifidobacteria) begin to die almost immediately after defecation, unless they are placed in a special transport medium.
Maximum permissible storage periods
The question of how many specific hours a sample can be stored is one of the most common. Standard laboratory protocols set strict limits. For most bacteriological studies, the shelf life of biomaterial collected in a sterile container without a preservative is no more than 2-3 hours if stored in the refrigerator.
If you use special containers with a transport medium (for example, Cary-Blair or similar gel bases), the period may be increased. In such cases, the material remains stable for up to 24 hours, and sometimes up to 48 hours, but only with strict adherence to the temperature regime. However, for classical culture for dysbacteriosis, “fresh” samples are most often required.
Consider the dependence of the quality of the analysis on time:
- 🕒 0–2 hours: Ideal time for delivery. The composition of the microflora corresponds to the state at the time of defecation.
- ❄️ 2–4 hours: Permissible limit for storage in the refrigerator. Minimal distortions in the number of anaerobes are possible.
- 📉 More than 5 hours: High risk of obtaining a false result. The active proliferation of foreign flora and the death of sensitive bacteria begins.
⚠️ Attention: If more than 4-5 hours have passed since defecation, there is no point in submitting such material for dysbacteriosis - the result will be unreliable.
Some laboratories may accept material collected the evening of the previous day, but only if it was placed in a special preservative immediately after collection. Under normal home conditions, without professional reagents, you should not count on this. It is better to plan the collection of biomaterial for early morning.
Rules for collecting biomaterial for an accurate result
The quality of the analysis directly depends on how correctly the collection was carried out. For the study, you need a medium portion of processed stool. Liquid feces are collected using a pipette built into the lid of the container in a volume of at least 5 ml.
The collection process should take place under the most sterile conditions. Do not allow urine, toilet water, or toilet paper to get into the sample. These impurities may contain foreign bacteria or chemicals that will suppress the growth of beneficial microflora in the nutrient medium.
Algorithm for collection:
- Prepare a sterile container with a spoon in advance.
- Free the surface of the toilet bowl from water (you can use a clean plastic film or a special vessel).
- Perform a bowel movement.
- Use a spoon to select material from 3-4 different places (especially if there is mucus or streaks of blood).
- Close the lid tightly to prevent air from entering.
It is important to use sterile containerbought at a pharmacy. The use of food jars (even thoroughly washed) is unacceptable, since microparticles of detergents or organic matter may remain on their walls, which will affect the growth of bacteria.
☑️ Preparation for collecting analysis
Storage features for different groups patients
Collecting tests from young children and bedridden patients has its own nuances, which may affect the timing and conditions of storage. Infants may have irregular stools, so parents often try to collect material in advance, “just in case.” This cannot be done.
For breastfed infants, the intestinal microflora is very labile. Any change in temperature or long-term storage will lead to the fact that the bifidobacteriaforming the basis of the baby's flora will die. Therefore, for children the rule “collected - lucky” applies.
Table of comparison of conditions for different groups:
| Group of patients | Optimal period | Acceptable period (refrigerator) | Features |
|---|---|---|---|
| Adults | Up to 2 hours | Up to 3-4 hours | Designed chair |
| Infants | Up to 1 hour | No more than 2 hours | Liquid stools, high sensitivity of flora |
| Patients on antibiotics | Immediately | Not recommended | High risk of distortion of dynamics |
| Elderly people | Up to 2 hours | Up to 3 hours | Often formed, dense stool |
If the child goes to the toilet only at night, try to collect the material in a clean pot (after pouring boiling water over it) and immediately place it in the refrigerator. In the morning, as soon as you wake up, immediately take the sample to the laboratory.
⚠️ Attention: For children under one year old, collecting feces from a diaper or diaper is not recommended, since the filler absorbs the liquid fraction, leaving only dense particles, which distorts the analysis.
Choice of container and transport medium
The type of container determines how long the bacteria will remain alive. Standard plastic cups with spoon are only suitable for quick delivery. If you plan to store the material, it is better to purchase containers with a preservative.
Transport medium is a special gel or liquid that stabilizes the pH and prevents the sample from drying out. Under such conditions, bacteria “fall asleep” and do not multiply. However, even with a preservative, you should not exceed the daily storage limit.
Where to buy special containers?
Sterile containers with transport medium are sold in large pharmacies, medical equipment stores, or issued directly from paid laboratories when ordering an analysis at home. Regular empty sterile cups are available in any pharmacy.
When choosing a container, pay attention to the labeling. The lid or side should indicate that the container is sterile. If the packaging is damaged or the expiration date has expired, such a container cannot be used - sterility is compromised, and foreign microorganisms could have entered it from the air.
Frequent errors when preparing for analysis
Even observing the time frame, patients often make mistakes that reduce the effectiveness of the study to zero. One of the most common is taking medications before taking the test.
Antibiotics, laxatives, bismuth and iron preparations can significantly change the color, consistency and bacterial composition of stool. Antibiotics should be discontinued at least 3-5 days before the test (in consultation with the doctor), and laxatives and rectal suppositories - 2-3 of the day.
List of common mistakes:
- 🚫 Collection of material during menstruation (blood gets into the sample).
- 🚫 Using an enema before collection (the natural one is washed out flora).
- 🚫 Storing the container on the refrigerator door (there the temperature fluctuates when opened).
- 🚫 Collecting stool after an X-ray with barium (barium inhibits the growth of bacteria).
It is also important to follow a diet 2-3 days before the analysis. Eliminate foods that cause fermentation (cabbage, legumes, brown bread) and alcohol. This will help to get a more objective picture of the work of the intestines.
Questions and answers (FAQ)
Is it possible to test feces for dysbacteriosis if it has been in the refrigerator for the entire night?
It is highly not recommended to submit such material. Overnight (8-10 hours), even at low temperatures, the composition of the microflora will have time to change: anaerobes will die, and opportunistic flora may begin to predominate. The result will be unreliable, which will lead to incorrect treatment.
What to do if it is not possible to take the analysis immediately after collection?
If a delay is unavoidable, use a container with a transport medium (preservative). Place it in the refrigerator (not the freezer!) and try to get it to the laboratory within the next 24 hours. The material cannot be stored without a preservative.
Does defrosting the container affect the result?
Yes, it has a fatal effect. If you accidentally freeze the container or it thaws after freezing, the sample is unusable. Ice crystals destroy the cell membranes of bacteria, and the laboratory technician will not be able to grow colonies from them.
Do you need to wash the container before collection?
No, if you are using a sterile pharmacy container, you cannot wash or rinse it with water - you will break the sterility and wash away the special treatment. Open it immediately before collecting.