Stool Culture: A Diagnostic Test for Gastrointestinal Infections


Stool culture is a diagnostic laboratory test used to identify and determine the presence of bacterial pathogens in the gastrointestinal tract. It plays a crucial role in diagnosing and guiding the treatment of gastrointestinal infections. In this article, we will explore the importance of stool culture, how the test is conducted, its indications, and what patients can expect during the process.

I. Purpose and Importance of Stool Culture

Stool culture is primarily performed to detect and identify bacterial pathogens that cause gastrointestinal infections. These infections, commonly known as bacterial gastroenteritis, can lead to symptoms such as diarrhea, abdominal pain, vomiting, and fever. By identifying the specific bacteria involved, healthcare providers can tailor appropriate treatment strategies to combat the infection effectively.

II. How Stool Culture is Conducted

The stool culture process involves several steps to isolate and identify bacteria. Here is an overview of the typical procedure:

  1. Sample Collection: To perform a stool culture, a small sample of stool is collected by the patient in a sterile container provided by the pharmacy store. Follow the instructions provided below in this article for proper collection and handling to ensure accurate results.
  2. Laboratory Analysis: The collected stool sample is sent to a laboratory for analysis. In the lab, a portion of the stool is placed onto different culture media that encourage the growth of various types of bacteria. These media contain nutrients that support bacterial growth and may also contain specific ingredients to selectively promote the growth of certain types of bacteria.
  3. Incubation: The culture plates or tubes containing the stool sample are then placed in an incubator, which provides optimal conditions for bacterial growth. The incubation period typically ranges from 24 to 48 hours, although some bacterial species may require longer incubation times.
  4. Identification and Sensitivity Testing: After the incubation period, trained laboratory personnel examine the culture plates for the presence of bacterial colonies. These colonies are further analyzed to identify the specific bacteria causing the infection. Additionally, antibiotic sensitivity testing may be performed to determine which antibiotics are effective in treating the infection.
  5. Reporting Results: Once the identification and sensitivity testing are complete, the laboratory generates a report with the results. The report indicates the presence or absence of pathogenic bacteria and provides information on the antibiotic susceptibility pattern, helping guide the choice of appropriate treatment.

III. How Stool Sample is Properly Collected

Proper collection and handling of a stool sample are crucial to ensure accurate results in a stool culture test. Here are instructions to help you collect the sample correctly:

  1. Collecting the Sample:
    • Begin by obtaining a clean, sterile container from your pharmacy store or a laboratory. Ensure that the container is tightly sealed to prevent leakage.
    • It is essential to collect a fresh sample. Choose a bowel movement that is relatively soft or has not come into contact with urine or toilet water.
    • Use a clean, dry spoon or scoop provided with the container to collect a small portion of the stool sample. A teaspoon-sized amount is usually sufficient. Avoid touching the inside of the container or contaminating the sample with water, soap, or urine.
  2. Proper Hygiene:
    • Before collecting the sample, thoroughly wash your hands with soap and warm water. This helps minimize the risk of contaminating the sample with external bacteria.
    • Avoid using any disinfectants, sanitizers, or antiseptic wipes on your hands or the collection container, as they may interfere with the test results.
  3. Storage and Transportation:
    • After collecting the stool sample, promptly close the container tightly to prevent any leakage during transportation.
    • If there is a delay in transporting the sample to the laboratory, refrigerate it according to the specific instructions provided by your gastroenterologist or the laboratory. Do not freeze the sample unless instructed to do so.
    • Transport the sample to the laboratory as soon as possible. Follow any specific storage and transportation guidelines provided by your gastroenterologist or the laboratory.
  4. Providing Relevant Information:
    • Provide accurate and relevant information about your symptoms, including the duration, frequency, consistency of the stool, and any associated symptoms such as blood or mucus in the stool.
    • If you have been taking any medications, especially antibiotics, it is essential to inform your gastroenterologist, as it may impact the interpretation of the stool culture results.

IV. What are the Most Common Mistakes Patients Make when Collecting Stool Samples?

Patients may unknowingly make certain mistakes when collecting stool samples for culture tests. These mistakes can potentially affect the accuracy of the results. Here are some of the most common mistakes patients make in stool culture:

  1. Using Inappropriate Collection Containers: Using non-sterile or improper collection containers can introduce contaminants into the sample, leading to inaccurate results. Obtain a sterile container specifically designed for stool sample collection from your pharmacy store or the laboratory.
  2. Contaminating the Sample: Touching the inside of the container, using a contaminated spoon or scoop, or allowing the sample to come into contact with water, urine, or toilet paper can introduce external bacteria into the sample. This contamination may interfere with the accurate identification of the bacterial pathogens causing the infection.
  3. Providing Insufficient Sample Quantity: Collecting an insufficient amount of stool may limit the laboratory’s ability to detect and identify bacterial pathogens accurately. Collect an adequate sample, usually a teaspoon-sized amount, to increase the chances of detecting any pathogens present.
  4. Delaying Sample Transportation: Stool samples should be transported to the laboratory as soon as possible after collection. Delaying transportation or storing the sample at room temperature for an extended period can affect the viability of the bacteria in the sample, leading to unreliable results. Follow any specific storage and transportation instructions provided by your gastroenterologist or the laboratory.
  5. Incorrectly Storing the Sample: Improper storage of the stool sample, such as freezing it when not instructed to do so, can impact the integrity of the bacteria in the sample and interfere with the accuracy of the results. Always follow the specific storage instructions provided by your gastroenterologist or the laboratory.
  6. Failing to Provide Relevant Information: Provide accurate and relevant information about your symptoms, including their duration, severity, and any associated symptoms. Additionally, informing your gastroenterologist about any recent antibiotic use or other medications is crucial, as it may affect the interpretation of the stool culture results.

V. Indications for Stool Culture

Stool culture is typically recommended in the following situations:

  1. Suspected Bacterial Gastroenteritis: When a patient presents with symptoms such as severe or prolonged diarrhea, bloody stools, high fever, or signs of systemic illness, stool culture is essential to identify the causative bacterial pathogen.
  2. Outbreaks or Public Health Concerns: In situations where there is an outbreak of gastrointestinal illness or when there are concerns about potential foodborne illnesses, stool culture is vital for identifying the specific bacteria responsible and implementing appropriate control measures.
  3. Travel-Related Infections: Individuals who have recently traveled to areas with poor sanitation or regions known for specific bacterial infections may undergo stool culture to identify any potential pathogens they may have acquired.
  4. Persistent or Recurrent Infections: In cases of recurring or persistent gastrointestinal infections, stool culture can help identify whether there is a chronic bacterial infection or reinfection occurring.

VI. Patient Experience and Considerations

For patients undergoing stool culture, here are some important considerations:

  1. Collection Instructions: Patients will receive specific instructions on how to collect a stool sample. It is crucial to carefully follow the instructions provided by the gastroenterologist to ensure accurate results.
  2. Sample Quantity: A small amount of stool, usually a teaspoon or a portion of a bowel movement, is sufficient for the test. The sample should be collected from different parts of the stool to increase the chances of detecting any pathogens present.
  3. Timing: Stool culture is most effective when performed during the acute phase of the infection. Therefore, it is important to collect the sample as soon as possible after the onset of symptoms.
  4. Results and Treatment: Once the stool culture results are available, the gastroenterologist will interpret the findings and determine the appropriate treatment plan based on the identified bacteria and their antibiotic susceptibility.
  5. Follow-Up: Maintain regular communication with the gastroenterologist after the stool culture to assess treatment effectiveness and address any concerns or questions that may arise.

Bottom Line

Stool culture is a valuable diagnostic tool for identifying bacterial pathogens responsible for gastrointestinal infections. By isolating and identifying specific bacteria, healthcare providers can tailor effective treatment strategies to combat the infection. Patients undergoing stool culture should follow the instructions provided for sample collection and be prepared to communicate with their gastroenterologist to ensure appropriate management of their condition. With the aid of stool culture, gastroenterologists can provide targeted care and promote a speedy recovery for patients with bacterial gastroenteritis.

How can I contact gastroenterologist Dr. Zavos for an appointment?

Dr. Chris Zavos is a board-certified gastroenterologist and hepatologist, located in Thessaloniki Greece, and specifically in Kalamaria suburb, about 7 kilometres (4 miles) southeast of downtown Thessaloniki. His private office is at: Fanariou 8 street (near Aigaiou and Adrianoupoleos avenues), Kalamaria (Thessaloniki), Greece.

Thessaloniki International Airport is only 10 km away from his private office in Kalamaria and can be reached by taxi within 13 minutes from the airport.

Dr. Chris Zavos performs endoscopies at Bioclinic private hospital in downtown Thessaloniki (Mitropoleos 86 street).

You can contact Dr. Zavos at phone numbers: (+30)-6976596988 and (+30)-2311283833, or you can email him at Dr. Zavos responds to Greek and English languages.

Last update: 27 October 2023, 22:12


Gastroenterologist - Hepatologist, Thessaloniki

PhD at Medical School, Aristotle University of Thessaloniki, Greece

PGDip at Universitair Medisch Centrum Utrecht, The Netherlands

Ex President, Hellenic H. pylori & Microbiota Study Group