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Urine Culture

This post is also available in: हिन्दी (Hindi)

Why is the test done?

The Urine culture test is done

• To confirm if you have a urinary tract infection (UTI).

• To identify the microbe (bacteria or fungus) causing the infection.

• To identify what drug works the best for the infective microbe.

• To know if the treatment is successful.

When is it done?

This test is done when a person shows symptoms of urinary tract infection such as

• Increased frequency of urination

• Painful urination

• Fever with chills

• Cloudy urine with foul smell

It is also done when your urine routine test raises suspicion or indicates the presence of urinary tract infection (UTI).

What sample is needed, and how is it collected?

You need to collect about 50-60 ml of urine in a sterile manner.

This is done by taking a clean catch mid-stream urine sample by the following steps:

Wash hands: start with washing your hands and then

Prepare the container: open the lid of the container provided by your doctor or lab technician. Avoid touching the inner surface of the container and keep it open at an easily accessible place.

Clean your genitals: you need to clean your genitals to preventing.

Men: retract the foreskin of your penis and clean the head of the penis properly. You may use medicated cotton swabs.

Women: spread apart the folds of the skin around your vagina using one hand. With the other hand, clean the area around the urethra and vagina properly. Clean the area from front to behind to avoid the spread of microbes from the anal region to the urethra.You may use medicated cotton swabs.

• Urinate: begin urinating into the urinal. Women need to continue holding the skin folds around the vagina to prevent contamination.

• Collect urine sample: after urinating for several seconds, bring the container to collect urine in mid-stream. Collect about 50 to 60ml of urine without interrupting the flow.

• Avoid following: avoid touching the container with your genitals. Avoid contaminating the sample with pubic hair, toilet paper, blood during periods, stools, and others.

• Finish urinating: complete urinating into the urinal and carefully close the container with the lid. Following this, wash your hands.

 

In special circumstances:

• Injured or bedridden patient: sample is collected by inserting a catheter into the bladder via the urethra.

Urethral problems or injuries: urine sample is drawn out by inserting a syringe directly into the urinary bladder through the abdomen.

Infants: the urine is collected using a bag attached near the genital.

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What preparations are required before the test?

Usually, no preparation is required for this test. However, few instructions can be given based on the type of culture.

• You may be asked not to go to the washroom for at least one hour before the test. This ensures you have enough urine for the test.

• If you have taken any antibiotics before the test, tell your doctor about this.This is because antibiotics can affect the results of the test.

What is tested?

The test examines the urine for the presence of a bacteria or a fungus. Identifying a pathogenic microbe in the urine suggests the presence of urinary tract infection.

Urine is a fluid that your kidneys produce when it filters the blood. It helps the body to remove excess water and waste products. It thus prevents the accumulation of toxins and maintain normal functioning.

When the blood circulates through the kidneys, it produces urine. The urine is then drained via the thin tubes called ureters into the urinary bladder. The bladder stores the urine for some time and prevent its continuous dribbling out of the body.

Urethritis: When the infective microbe gets access to the urethra, it may multiply and cause an infection called urethritis.

Cystitis: The microbes may ascend up from urethra into the urinary bladder. There it may multiple further causing infection of the bladder called cystitis.

The above-mentioned infection types are called the lower urinary tract infection (lower UTI). This is more common and relatively has better outcomes.

Pyelonephritis: Sometimes, the microbes may travel up through the ureters into the kidneys where it causes pyelonephritis or upper UTI. This is less common but more severe form of infection with serious outcomes. The infection may spread from kidneys to the blood, which may cause a life-threatening condition called sepsis.

People with predisposing conditions such as kidney disease, diabetes, kidney stones, or weak immunity are more prone to get urinary tract infection.

How the urine culture test works?

The collected urine sample is made to go through several processes to find out the following:

 

Confirm the presence of infection:

The microbes that cause UTI remain accumulated within the urine. Thus, collecting a sample of urine for the detection of the microbes allows us to confirm the presence of infection.

 

Identify the cause of infection:

The urine sample is put over a special dish containing a material (agar) that promotes microbial growth. On receiving an appropriate medium, the microbes grow into large numbers forming colonies. Identifying these colonies helps to know the cause of infection.

Typically, it takes about 1 to 2 days for the microbes to form colonies. This is then looked under the microscope to know the followings:

• Number of colonies- indicates the amount of microbes present in your urine sample.

• Types- whether one or multiple bacteria are present in the sample.

• Size, shape, and color- identifies the type of the bacteria

The samples from each colony are used for other tests such as gram stain, which further identifies the microbe.

If there is no growth of the microbes even after 1 to 2 days, then it is considered negative for infection.

 

Identify if the sample collected is clean or contaminated:

1. Clean catch sample- will typically show a single type of microbe/bacteria. Moreover, it will show a specific type of microbe that causes a UTI.

2. Contaminated sample- when more than one type of microbe grows on the medium, it usually indicates contamination of the urine sample. This occurs due to contamination from skin, feces, or vagina while collecting the sample. Sometimes, it might suggest an infection with more than one microbe.

 

Identify the drug that works:

To identify what medicine works for the organism, the doctor would put some specific drugs over the grown microbes. This test is called an antibiotic sensitivity test or susceptibility test. The killing of the grown bacteria in the dish suggests a response to the drug.

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What does the test result mean?

The result of the urine culture test is interpreted in correlation with urine analysis results and symptoms. The doctor would also consider how the urine sample was taken or whether you had any symptoms at the time of sample collection.

The result of Urine culture typically comes in 1 to 3 days. However, some microbes take longer to grow, with results available only after several days.

 

Urine culture

 

Normal• No growth of any microbe (bacteria or fungus) in the medium suggest negative result– usually suggesting you have no infection.

• This is especially applicable if the symptoms and urinalysis report also suggests no obvious infection.

Note: However, if your symptoms persist, then urine culture may be repeated on another sample. In the 2nd sample, the doctor will try to find the bacteria at lower colony counts or other microbes that can cause infection.

AbnormalThe growth of one type of microbe or bacteria in a properly collected sample suggests positive results.

• High chances of UTI: 100,000 or more bacteria/ml of urine suggest high chances of an infection.

• Moderate chances of UTI: count of 1000 to 100,000 bacteria/ml may indicate infection or contamination of the urine sample. You may need to repeat the test. However, if you have significant symptoms,it increases the chances of UTI.

• Unlikely UTI: count of 1000 or less, indicates unlikelihood of infection. However, you can have a count of 1000 or less if you have already started antibiotics. This count may also suggest infection if the urine sample is taken with a catheter that minimizes its contamination.

Contamination• If a urine culture shows different types of bacterial growth, then it likely suggests contamination of the urine.This is more likely if the urine sample in a woman grows Lactobacillus or other common bacteria normally present in the vagina

• If the symptoms of UTI persists, then your doctor may ask to repeat the test on a sample taken more care with all the aseptic precautions.

• If one type of bacteria has significantly higher counts than the other- e.g., 100,000 bacteria/mL versus 1,000 bacteria/mL, then further testing may be required to identify the predominant bacteria

 

Positive results:

If the urine culture result is positive, then the susceptibility test may be done to know which drug works best for the microbe causing UTI in you. It helps the doctor to plan your treatment with better results.

Several types of bacteria may cause UTI. However, the E. coli, which normally exists in the digestive tract, is commonly found to cause UTI.

Some of the other bacteria that may cause UTI are given below:

• Staphylococcus

• Acinetobacter

• Klebsiella

• Proteus

• Enterobacter

Occasionally, urinary tract infection can also happen because of yeast, such as Candida albicans.

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