Bacterial culture in gynecology: what this test is and how to read the result

A bacterial culture is a laboratory test in which a sample is placed on a nutrient medium and the microorganisms that grow are observed. Bacteria live almost everywhere in the body and on the skin: some are harmless or even beneficial, others cause infections. A culture helps to understand which bacteria are associated with an infection.

What a bacterial culture is and what it determines

A bacterial culture (from "bacteriological culture") is a method of cultivating microorganisms on nutrient media for culture-based diagnostics. A culture determines whether there is a bacterial infection and which bacterium causes it. In the laboratory, the material is placed in a dish with a special medium where microorganisms grow. On a solid medium, a single colony-forming unit grows into a colony — a visible cluster of microorganisms of one species. Taking a swab carries no known risks.

Why material is grown on a nutrient medium

To identify the species of bacteria, many cells need to be examined, and most samples do not contain enough of them — so the material is sent to a medium where the microorganisms multiply to the required amount. Most pathogenic bacteria need one to two days, but some grow for five days or longer, so the report form may be ready after several days. A sensitivity test to antibiotics is performed separately: it shows which drugs the grown bacteria respond to — this helps to select treatment.

Where the material is taken from

Where exactly the sample is taken from depends on where the infection is suspected — this is determined by the doctor. If bacterial vaginosis is suspected, during the examination a cotton swab may be passed over the discharge in the vagina to check for both bacterial vaginosis and other infections. The preparation rules differ for different types of culture, so they should be asked from the person who ordered the test.

Indications: when a bacterial culture is ordered, including during pregnancy

A referral is given when there are symptoms of a bacterial infection, and they depend on which organ is involved. In bacterial vaginosis, these are unusual discharge with a strong fishy odor, especially after sex, a change in color and consistency — grayish-white, thin, watery. About half of women have no symptoms, and the condition usually does not cause pain or itching. At the appointment, the doctor asks about complaints, examines the vagina and rules out sexually transmitted infections. Bacterial vaginosis is not classified as an STI, but sexual activity can provoke it, and it can be passed to a person with a vagina.

If bacterial vaginosis occurs during pregnancy, there is a small chance of complications — preterm birth or miscarriage, although in most pregnancies it causes no problems. If the nature of the discharge changes during this period, you need to talk to a doctor or midwife.

How to read the interpretation: microorganisms and sensitivity

The interpretation of a bacterial culture is based on several points. The first is which microorganisms grew: if harmful bacteria are found, this usually means a bacterial infection, and the laboratory names the causative agent. The second is the sensitivity test to antibacterial drugs. In addition, the doctor may order additional examinations — to confirm the diagnosis or assess how serious the infection is.

• the name of the microorganism that grew;
• a conclusion on whether harmful bacteria were found;
• the result of the antibiotic sensitivity test;
• if necessary — additional examinations to confirm the diagnosis or assess severity.

What the result does not show and when to discuss it with a doctor

Based on a single culture result, the doctor may order additional tests. A culture also does not explain how closely the found microorganism is related to the complaints: some bacteria are harmless, so the report form is compared with the examination and other tests. If there is no bacterial infection, antibacterial drugs are not needed: taking such medicines without indications leads to bacterial resistance. You should discuss the result with a doctor if symptoms persist or if you are pregnant and the nature of the discharge has changed.

A bacterial culture by itself is not a reason to call an ambulance; 103/112 — for life-threatening conditions: signs of stroke, heart attack or severe injury.

This material is for reference: it does not replace a doctor's consultation, and it is calmer to discuss the report form together with a partner at a specialist's appointment.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer