Urine Culture: What Is It And What Is It For?

Urinary tract infections (UTIs) are very common pathologies. Scientific studies estimate that 50% to 60% of women will experience the condition in their lifetime. Many different germs can cause them, so urine cultures are used to detect a specific causative agent .

In 1995, the direct and indirect cost of these infections in the United States reached $2,000 million annually. Of course, knowing how to identify the pathogen that causes each case is essential for a patient’s speedy recovery. Let’s see how important urine culture is in this process .

What is urine culture for?

First of all, it should be emphasized that urine culture and urinalysis are not the same. The latter study consists of a series of tests that are applied to the patient’s sample. Among other things, they include macroscopic, microscopic and physicochemical examinations.

In special cases, however, it is considered necessary to also culture the urine at the end.

Therefore, not all urine tests require a urine culture to diagnose a patient. It is taken into account when a specialist doctor suspects a urinary tract infection in adults and children. This is according to the recommendations of the National Library of Medicine in the United States.

How is a urine sample collected?

In most cases, a urine sample is collected by the patient at home and then taken to a trusted health center or laboratory. Clinical microbiology specialists will detail each step in detail to guide patients.

Obtaining a sample

This is a key step in the urine collection process as the fluid can become contaminated with commensal bacteria from the patient’s skin and genitourinary tract. In general, laboratories will consider any sample containing less than 5% contaminant fit for testing.

There are several ways to sample, but we will focus on the most common of them. When a patient needs to urinate into a container at home and then take it to the clinic. In this procedure, consider the following guidelines:

• Before taking the sample, you should thoroughly wash the intimate area to prevent contamination.
• The patient should collect the first morning urine because it is the most concentrated.
• It is not necessary to force fluid intake prior to sampling, as the urine would then be diluted.

• It is recommended to collect a volume of 25 to 50 milliliters. The minimum amount at which urine may be cultured is 3 milliliters.

Note that, according to Anales de Pediatría, the sample can also be taken by other techniques such as bladder puncture or temporary bladder catheterization. They are more aseptic than urination, but are much more invasive procedures that are only used in exceptional cases.

What about the sample on which the urine is cultured?

According to the medical portals already mentioned, there are several different analyzes that are performed on urine cultures, although the most common is microbiological culture. Below we explain a little more how this specialized examination works:

• A seeding loop is used and the urine sample is spread over a bacterial growth medium, usually consisting of an agar nutrient mix as the base in a petri dish.

• The seeded sample is incubated for 16 or 18 hours at 35-37 ° C.
• After incubation, the colonies of bacteria that have grown – or not – on the plate, are counted.

The premise is simple: if bacteria are present in the patient’s urine, they will multiply in the urine culture. This allows us to know if a person is infected or not. Then, by further testing – or using a specific agent for that pathogen – the exact causative agent of the infection will be determined.

Symptoms of urinary tract infections

The question of whether you need a urine culture to resolve a discomfort that persists for a long time can sometimes present a problem. Therefore, we present below the most common symptoms of urinary tract infections that may require it. The Mayo Clinic shows the following symptoms:

• Urgent and constant need to urinate.

• A burning sensation when urinating.
• Urine that is cloudy, red, or has a strong odor.
• Pain in the pelvic area in women.

Depending on the part of the genitourinary system where the bacterial colonies have settled, symptoms will vary. Nevertheless, the presence of the symptoms already described and episodes of fever and abdominal discomfort are very common.

Urine culture results

The test results are relatively easy to interpret. A normal proliferation value means everything is fine, which rules out a bacterial infection in the patient. On the other hand, a positive test result indicates the presence of bacteria or fungi in some area of ​​the urinary tract.

In such situations, the patient’s specialist physician will determine the appropriate antibiotic or antifungal agent as needed. Be sure to follow your doctor’s instructions closely, as stopping treatment before the allotted time is over may complicate the progression of your condition.

Urine culture in pregnancy: is it an important test?

According to Inatal, urine culture is particularly important during pregnancy. Pregnant women have a greater predisposition to bacterial infections due to the physiological changes that occur during pregnancy.

Additionally, many of these infections are asymptomatic. A urinary tract infection, even if it does not cause clinical symptoms in the mother, can also lead to undesirable complications such as an increased risk of preterm labor.

What is the importance of urine culture

As we have seen in this article, urine culture is one of the tests performed as part of urinalysis when a doctor suspects a patient has an infection. This simple laboratory technique allows the pathogen to be isolated and identified in any case.

Collecting a sample is very simple and can be done at home, although there are exceptional cases that require punctures and catheters. Negative culture indicates the absence of bacteria in the patient’s urogenital tract. However, a long-term urine culture requires the use of antibiotics or antifungal drugs.