Culture Blood – Indications, Procedures, Results

Bile culture

Culture – bile

Bile culture is a laboratory test to detect disease-causing germs in the biliary system.

How the Test is Performed

A sample of bile is needed. This can be done using different methods, including gallbladder surgery or a procedure called endoscopic retrograde cholangiopancreatography ( ERCP ).

The bile sample is sent to a lab. There, it is placed in a special dish called a culture medium to see if bacteria, viruses, or fungi grow on the sample.

How to Prepare for the Test

Preparation depends on the specific method used to obtain the bile sample. Follow your health care provider’s instructions exactly.

How the Test will Feel

If bile is taken during gallbladder surgery, you will feel no pain because you are asleep.

If bile is taken during ERCP, you will receive medicine to relax you. You may have some discomfort as the endoscope passes through your mouth, throat, and down the esophagus. This feeling will go away shortly. You may also be given medicine (anesthesia) so that you will sleep lightly for this test. If you are asleep, you will not feel any discomfort.

Why the Test is Performed

This test is done to detect infection within the biliary system. The biliary system creates, moves, stores, and releases bile to help indigestion.

Normal Results

The test result is normal if no bacteria, virus, or fungus grew in the laboratory dish.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result means bacteria, fungus, or a virus grew in the laboratory dish. This may be a sign of infection.

Risks

Risks depend on the method used to take a sample of the bile. Your health care provider can explain these risks.

Blood culture

Culture – blood

A blood culture is a laboratory test to check for bacteria or other germs in a blood sample.

How the Test is Performed

A blood sample is needed .

The site where blood will be drawn is first cleaned with an antiseptic such as chlorhexidine. This reduces the chance of an organism from the skin getting into (contaminating) the blood sample and causing a false-positive result (see below).

The sample is sent to a laboratory. There, it is placed in a special dish (culture). It is then watched to see if bacteria or other disease-causing germs grow. A gram stain may also be done. A gram stain is a method of identifying bacteria using a special series of stains (colors). With some infections, bacteria can be found in the blood only intermittently. So, a series of three or more blood cultures may be done to increase the chance of finding the infection.

How to Prepare for the Test

There is no special preparation.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

Your health care provider may order this test if you have symptoms of a serious infection, also known as sepsis . Symptoms of sepsis can include high fever, chills, rapid breathing and heart rate, confusion, and low blood pressure.

The blood culture helps identify the type of bacteria causing the infection. This helps your provider determine how best to treat the infection.

Normal Results

A normal value means that no bacteria or other germs were seen in your blood sample.

What Abnormal Results Mean

An abnormal (positive) result means that germs were identified in your blood. The medical term for this is bacteremia. This can be the result of sepsis. Sepsis is a medical emergency and you will be admitted to a hospital for treatment.

Other types of germs, such as a fungus or a virus, may also be found in a blood culture.

Sometimes, an abnormal result can be due to contamination. This means bacteria may be found, but it came from your skin or from the lab equipment, instead of your blood. This is called a false-positive result. It means you do not have a true infection.

Risks

Veins and arteries vary in size from one patient to another, and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

Bone marrow culture

Culture – bone marrow

Bone marrow culture is an examination of the soft, fatty tissue found inside certain bones. The bone marrow tissue produces blood cells. This test is done to look for an infection inside the bone marrow.

How the Test is Performed

The doctor removes a sample of your bone marrow from the back of your pelvic bone or front of your breast bone. This is done with a small needle inserted into your bone. The process is called a bone marrow aspiration or a biopsy .

The tissue sample is sent to a lab. It is placed into a special container called a culture dish. The tissue sample is examined under a microscope each day to see if any bacteria, fungi, or viruses have grown.

If any bacteria, fungi, or viruses are found, other tests may be done to learn which drugs will kill the organisms. Treatment can then be adjusted based on these results.

How the Test will Feel

You may feel pressure and pain as the marrow is being removed. You may be given some numbing medicine, called local anesthesia, before the procedure.

Soreness at the site usually lasts from a few hours up to 2 days.

Why the Test is Performed

You may have this test if you have an unexplained fever or if your health care provider thinks you have an infection of the bone marrow.

Normal Results

No growth of bacteria, viruses, or fungi in the culture is normal.

What Abnormal Results Mean

Abnormal results suggest that you have an infection of the bone marrow. The infection may be from bacteria, viruses, or fungi.

Risks

There may be some bleeding at the puncture site. More serious risks, such as serious bleeding or infection, are very rare.

Bronchoscopic culture

Culture – bronchoscopic

Bronchoscopic culture is a laboratory exam to check a piece of tissue or fluid from the lungs for infection-causing germs.

How the Test is Performed

A procedure called bronchoscopy is used to get a sample ( biopsy ) of lung tissue or fluid.

The sample is sent to a laboratory. There, it is placed in a special dish (culture). It is then watched to see if bacteria or other disease-causing germs grow. Treatment is based on the results of the culture.

How to Prepare for the Test

Follow your health care provider’s instructions on how to prepare for bronchoscopy.

How the Test will Feel

Your provider will tell you what to expect during bronchoscopy.

Why the Test is Performed

A bronchoscopic culture is done to find infection in the lung that cannot be accurately detected by a sputum culture . The procedure may find the following things, such as:

  • Abnormal secretions
  • Abnormal lung tissue
  • Abscesses
  • Inflammation
  • Obstructive lesions, such as cancer or foreign bodies

Normal Results

No organisms are seen on the culture.

What Abnormal Results Mean

Abnormal culture results usually indicate a respiratory infection. The infection may be caused by bacteria, viruses, parasites, mycobacteria, or fungi. The results of the culture will help determine the best treatment.

Not all organisms found with bronchoscopic culture need to be treated. Your provider will tell you more about this if needed.

Risks

Your provider can discuss the risks of the bronchoscopy procedure with you.

Endocervical culture

Vaginal culture; Female genital tract culture; Culture – cervix

Endocervical culture is a laboratory test that helps identify infection in the female genital tract.

How the Test is Performed

During a vaginal examination, the health care provider uses a swab to take samples of mucus and cells from the endocervix. This is the area around the opening of the uterus. The samples are sent to a lab. There, they are placed in a special dish (culture). They are then watched to see if bacteria, virus, or fungus grow. Further tests may be done to identify the specific organism and determine the best treatment.

How to Prepare for the Test

In the 2 days before the procedure:

  • Do NOT use creams or other medicines in the vagina.
  • Do NOT douche. (You should never douche. Douching can cause infection of the vagina or uterus.)
  • Empty your bladder and bowel.
  • At your provider’s office, follow instructions for preparing for the vaginal exam.

How the Test will Feel

You will feel some pressure from the speculum. This is an instrument inserted into the vagina to hold the area open so that the provider can view the cervix and collect the samples. There may be a slight cramping when the swab touches the cervix.

Why the Test is Performed

The test may be done to determine the cause of vaginitis , pelvic pain, an unusual vaginal discharge , or other signs of infection.

Normal Results

Organisms that are usually present in the vagina are there in the expected amounts.

What Abnormal Results Mean

Abnormal results indicate the presence of an infection in the genital tract or urinary tract in women, such as:

  • Genital herpes
  • Chronic swelling and irritation of the urethra ( urethritis )
  • Gonorrhea or chlamydia
  • Pelvic inflammatory disaese (PID)

Risks

There may be slight bleeding or spotting after the test. This is normal.

Culture – colonic tissue

Colonic tissue culture

A colonic tissue culture is a lab test to check for the cause of disease. The sample of tissue for the test is taken from the large intestine. The cause may be bacteria, fungi, or viruses.

How the Test is Performed

The health care provider removes a piece of tissue from your large intestine. This is done during a colonoscopy .

  • The sample is sent to a lab.
  • It is placed in a special dish that contains a gel. Bacteria and other organisms can grow in this gel. The dish is then stored at a certain temperature.
  • The lab team checks the sample daily. They check to see if bacteria, viruses, or fungi have grown.

If certain germs grow, more tests will be done to identify them. This helps decide the best treatment.

How to Prepare for the Test

There is no specific preparation needed for a culture.

How the Test will Feel

Once the sample is taken, the culture does not involve you. Therefore, there is no pain.

Why the Test is Performed

Your provider may order this test if you have signs or symptoms of a large intestine infection. A culture is often done when other tests such as a stool culture could not identify the cause of infection.

Normal Results

A normal result means that no disease-causing organisms have grown in the lab dish.

Some “healthy” bacteria, called bowel flora, are normally found in the gut. The growth of such bacteria during this test does not mean there is an infection.

Normal value ranges may vary slightly among different laboratories. Talk to your provider about your test results.

What Abnormal Results Mean

An abnormal result means that disease-causing organisms have grown in the lab dish. These organisms may include:

  • Clostridium difficile bacteria
  • Cytomegalovirus
  • Mycobacterium tuberculosis bacteria
  • Salmonella bacteria
  • Shigella bacteria

These organisms may lead to diarrhea or colon infections.

Risks

There are no risks in a colonic tissue culture.

Cerebrospinal fluid (CSF) culture

Culture – CSF; Spinal fluid culture; CSF culture

A cerebrospinal fluid (CSF) culture is a laboratory test to look for bacteria, fungi, and viruses in the fluid that moves in the space around the spinal cord. CSF protects the brain and spinal cord from injury.

How the Test is Performed

A sample of CSF is needed. This sample is usually done with a lumbar puncture, or a spinal tap .

The sample is sent to the laboratory. There, it is placed in a special dish called a culture medium. Laboratory staff then observe if bacteria, fungi, or viruses grow in the dish. Growth means there is an infection.

How to Prepare for the Test

Follow instructions on how to prepare for a spinal tap .

Why the Test is Performed

Your health care provider may order this test if you have signs of an infection that affects the brain or nervous system. The test helps identify what is causing the infection. This will help your provider decide on the best treatment.

Normal Results

A normal result means no bacteria, viruses, or fungi grew in the laboratory dish. This is called a negative result. However, a normal result doesn’t mean that there is no infection. The spinal tap and CSF smear may need to be done again.

What Abnormal Results Mean

Bacteria or other germs found in the sample may be a sign of meningitis. This is an infection of the membranes covering the brain and spinal cord. The infection can be caused by bacteria , fungi, or viruses.

Risks

A laboratory culture poses no risk to you. Your provider will tell you about the risks of a spinal tap .

Culture – duodenal tissue

Duodenal tissue culture

A duodenal tissue culture is a laboratory exam to check a piece of tissue from the first part of the small intestine (duodenum). The test is to look for organisms that cause infection.

How the Test is Performed

A piece of tissue from the first part of the small intestine is taken during an upper endoscopy ( esophagogastroduodenoscopy ).

The sample is then sent to a lab. There it is placed in a special dish (culture media) that allows bacteria or viruses to grow. The sample is looked at under a microscope regularly to see if any organisms are growing.

Organisms that grow on the culture are identified.

How to Prepare for the Test

This is a test done in a lab. The sample is collected during an upper endoscopy and biopsy procedure (esophagogastroduodenoscopy). Ask your health care provider how to prepare for this procedure.

Why the Test is Performed

A culture of duodenal tissue is done to check for bacteria or viruses that may lead to certain illnesses and conditions.

Normal Results

No harmful bacteria or viruses are found.

What Abnormal Results Mean

An abnormal finding means that harmful bacteria or a virus has been found in the tissue sample. Bacteria may include:

  • Campylobacter
  • Helicobacter pylori
  • Salmonella

Considerations

Other tests are very often done to look for infection-causing organisms in duodenal tissue. These tests include the urease test (for example, the CLO test) and histology (looking at the tissue under a microscope).

Routine culture for H pylori is not currently recommended.

Ear drainage culture

Culture – ear drainage

An ear drainage culture is a lab test. This test checks for germs that can cause infection. The sample taken for this test can contain fluid, pus, wax, or blood from the ear.

How the Test is Performed

A sample of ear drainage is needed. Your health care provider will use a cotton swab to collect the sample from inside the outer ear canal. In some cases, a sample is collected from the middle ear during ear surgery.

The sample is sent to a lab and placed on a special dish (culture media).

The lab team checks the dish every day to see if bacteria, fungi, or viruses have grown. More tests may be done to look for specific germs and determine the best treatment.

How to Prepare for the Test

You do not need to prepare for this test.

How the Test will Feel

Using a cotton swab to take a sample of drainage from the outer ear is not painful. However, ear pain may be present if the ear is infected.

Ear surgery is done using general anesthesia. You will be asleep and feel no pain.

Why the Test is Performed

The test may be done if you or your child has:

  • An ear infection that is not getting better with treatment
  • An infection of the outer ear ( otitis externa )
  • An ear infection with a ruptured eardrum and draining fluid

It may also be done as a routine part of myringotomy .

Note: Ear infections are diagnosed based on symptoms rather than using a culture.

Normal Results

The test is normal if there is no growth on the culture.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may be a sign of an infection. The infection can be caused by bacteria, virus, or fungus.

The test results may show which organism is causing the infection. It will help your provider decide on the right treatment.

Risks

No risks are involved with swabbing the ear canal. Ear surgery may involve some risks.

Esophageal culture

Culture – esophageal

Esophageal culture is a laboratory test that checks for infection-causing germs in a sample of tissue from the esophagus.

How the Test is Performed

A sample of tissue from your esophagus is needed. The sample is taken during a procedure called esophagogastroduodenoscopy (EGD) .

The sample is sent to a lab. There, it is placed in a special dish (culture) and watched for the growth of bacteria, fungi, or viruses.

Other tests may be done to determine what medicine can best treat the organism.

How to Prepare for the Test

Follow your health care provider’s instructions on how to prepare for EGD.

How the Test will Feel

During EGD, you will receive medicine to relax you. You may have some discomfort or feel like gagging as the endoscope is passed through your mouth and throat into the esophagus. This feeling will go away shortly.

Why the Test is Performed

Your doctor may order this test if you have signs or symptoms of an esophageal infection or disease. You may also have the test if an ongoing infection does not get better with treatment.

Normal Results

A normal result means that no germs grew in the laboratory dish.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result means germs grew in the laboratory dish. This is a sign of an infection of the esophagus, which may be due to bacteria, a virus, or a fungus.

Risks

Risks are related to the EGD procedure. Your health care provider can explain these risks.

Skin or nail culture

Mucosal culture; Culture – skin; Culture – mucosal; Nail culture; Culture – fingernail; Fingernail culture

A skin or nail culture is a laboratory test to look for and identify germs that cause problems with the skin or nails.

It is called a mucosal culture if the sample involves the mucous membranes.

How the Test is Performed

The health care provider may use a cotton swab to collect a sample from an open skin rash or skin sore.

A sample of skin may need to be taken. This is called a skin biopsy . Before the skin sample is removed, you will likely receive a shot (injection) of numbing medicine to prevent pain.

A small sample of a fingernail or toenail may be taken. The sample is sent to a lab. There, it is placed in a special dish (culture). It is then watched to see if bacteria, viruses, or fungi grow. It may take up to 3 weeks to get results of a nail culture. Further tests can be done to identify the specific germ that is causing your problem. This can help your provider determine the best treatment.

How to Prepare for the Test

There is no preparation needed for this test. If a skin or mucosal sample is needed, your provider will tell you how to prepare.

How the Test will Feel

If a skin sample is taken, you may feel a sting when the shot of numbing medicine is given.

For a nail sample, the provider scrapes the affected area of the nail. There is usually no pain.

Why the Test is Performed

This test may be done to diagnose the cause of:

  • A bacteria or fungus infection of the skin, finger, or toenail
  • A skin rash or sore that appears to be infected
  • A skin ulcer that is not healing

Normal Results

A normal result means no disease-causing germs are seen in the culture.

Some germs normally live on the skin. These are not a sign of infection and are considered a normal finding.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result means bacteria, fungus, or virus is present. This may be a sign of infection.

Common skin infections caused by bacteria include:

  • Impetigo
  • Diabetes foot ulcers

Common skin infections caused by fungus include:

  • Athlete’s foot
  • Nail infections
  • Scalp infections

Risks

Risks include slight bleeding or infection in the area where the skin sample was removed.

Gastric tissue biopsy and culture

Culture – gastric tissue; Culture – stomach tissue; Biopsy – gastric tissue; Biopsy – stomach tissue; Upper endoscopy – gastric tissue biopsy; EGD – gastric tissue biopsy

Gastric tissue biopsy is the removal of stomach tissue for examination. A culture is a laboratory test that examines the tissue sample for bacteria and other organisms that can cause disease.

How the Test is Performed

The tissue sample is removed during a procedure called upper endoscopy (or EGD) . It is done with a flexible tube with a small camera (flexible endoscope) at the end. The scope is inserted down the throat into the stomach.

The health care provider sends the tissue sample to a laboratory where it is examined for signs of cancer, certain infections, or other problems.

How to Prepare for the Test

Follow instructions on how to prepare for the procedure. You will likely be asked not to eat or drink anything for 6 to 12 hours before the procedure.

How the Test will Feel

Your provider will tell you what to expect during the procedure.

Why the Test is Performed

This test may be done to diagnose a stomach ulcer or the cause of other stomach symptoms. These symptoms may include:

  • Loss of appetite or weight loss
  • Nausea and vomiting
  • Pain in the upper part of the belly
  • Black stools
  • Vomiting blood or coffee ground-like material

A gastric tissue biopsy and culture can help detect:

  • Cancer
  • Infections, most commonly Helicobacter pylori , the bacteria that can cause stomach ulcers

Normal Results

A gastric tissue biopsy is normal if it does not show cancer, other damage to the lining of the stomach, or signs of organisms that cause infection.

A gastric tissue culture may be considered normal if it does not show certain bacteria. Stomach acids normally prevent too much bacteria from growing.

What Abnormal Results Mean

Abnormal results may be due to:

  • Stomach (gastric) cancer
  • Gastritis , when the lining of the stomach becomes inflamed or swollen
  • Helicobacter pylori infection

Risks

Your provider can discuss the risks of the upper endoscopy procedure with you.

Urethral discharge culture

Culture of urethral discharge; Genital exudate culture; Culture – genital discharge or exudateUrethral discharge culture is a laboratory test done on men and boys. This test is used to identify germs in the urethra that may be causing  urethritis . The urethra is the tube that drains urine from the bladder.

How the Test is Performed

The health care provider uses sterile cotton or gauze to clean the opening of the urethra at the tip of the penis. To collect the sample, a cotton swab is then gently inserted about 3/4 inch (2 centimeters) into the urethra and turned. To get a good sample, the test should be done at least 2 hours after urinating.

The sample is sent to a lab. There, it is placed in a special dish (culture). It is then watched to see if bacteria or any other germs grow.

How to Prepare for the Test

Do NOT urinate for 1 hour before the test. Urinating washes away some of the germs needed for accurate test results.

How the Test will Feel

There is usually some discomfort from swabbing the urethra.

Why the Test is Performed

The provider often orders the test when there is a discharge from the urethra. This test can detect sexually transmitted infections (STIs), such as gonorrhea and chlamydia .

Normal Results

A negative culture, or no growth appearing in the culture, is normal.

What Abnormal Results Mean

Abnormal results can be a sign of infection in the genital tract. These infections can include gonorrhea or chlamydia.

Risks

Fainting may occur when the swab is introduced into the urethra. This is due to stimulation of the vagus nerve. Other risks include infection or bleeding.

Herpes viral culture of lesion

Culture – herpes simplex virus; Herpes simplex virus culture

Herpes viral culture of a lesion is a laboratory test to check if a skin sore is infected with the herpes simplex virus.

How the Test is Performed

The health care provider collects the sample from a skin sore (lesion) . The sample is sent to a lab. There, it is placed in a special dish (culture). It is then watched to see if the herpes simplex virus (HSV) or substances related to the virus grow. Special tests may also be done to determine whether it is HSV type 1 or 2.

How to Prepare for the Test

The sample must be collected during the acute phase of infection. This is the worst part of an outbreak. It is also when the skin lesions are at their worst.

How the Test will Feel

When the sample is collected, you may feel an uncomfortable scraping or sticky sensation. Sometimes a sample from the throat or eyes is needed. This involves rubbing a sterile swab against the eye or in the throat.

Why the Test is Performed

The test is done to confirm herpes simplex infection. The herpes virus causes genital herpes . It can also cause cold sores of the mouth and lips.

The diagnosis is often made by physical examination (the provider looking at the sores). The cultures and other tests are used to confirm the diagnosis.

This test is most likely accurate when a person is newly infected, that is, during the first outbreak.

Normal Results

A normal (negative) result means that the herpes simplex virus did not grow in the laboratory dish and the skin sample used in the test did not contain any herpes virus.

Be aware that a normal (negative) culture does not always mean that you do not have a herpes infection or have not had one in the past.

What Abnormal Results Mean

An abnormal (positive) result may mean that you have an active infection with herpes simplex virus. Herpes infections include herpes genitalis , which is genital herpes, or cold sores on the lips or in the mouth.

If the culture is positive for herpes, you may have recently become infected. You may have become infected in the past and are currently having an outbreak.

Risks

Risks include slight bleeding or infection in the area where the skin sample was removed.

Culture – joint fluid

Joint fluid culture

Joint fluid culture is a laboratory test to detect infection-causing organisms in a sample of fluid surrounding a joint.

How the Test is Performed

A sample of joint fluid is needed. This may be done in a doctor’s office using a needle, or during an operating room procedure. Removing the sample is called joint fluid aspiration .

The fluid sample is sent to a laboratory where it is placed in a special dish and watched to see if bacteria, fungi, or viruses grow. This is called a culture.

If these germs are detected, other tests may be done to further identify the infection-causing substance and determine the best treatment.

How to Prepare for the Test

There is no special preparation needed for the lab culture. How to prepare for the removal of joint fluid .

How the Test will Feel

The joint fluid culture is done in a laboratory and does not involve the person.

For information on how the procedure to remove joint fluid feels, see joint fluid aspiration .

Why the Test is Performed

Your doctor may order this test if you have unexplained pain and inflammation of a joint or a suspected joint infection.

Normal Results

The test result is considered normal if no organisms (bacteria, fungi, or viruses) grow in the laboratory dish.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results are a sign of infection in the joint. Infections may include:

  • Bacterial arthritis
  • Fungal arthritis
  • Gonococcal arthritis
  • Turberculous arthritis

Risks

There are no risks to the patient associated with a lab culture. For risks related to the removal of joint fluid, see joint fluid aspiration .

Lymph node culture

Culture – lymph node

Lymph node culture is a laboratory test done on a sample from a lymph node to identify germs that cause infection.

How the Test is Performed

A sample is needed from a lymph node. The sample may be taken using a needle to draw fluid (aspiration) from the lymph node or during a lymph node biopsy .

The sample is sent to a laboratory. There, it is placed in a special dish and watched to see if bacteria, fungi, or viruses grow. This process is called a culture. Sometimes, special stains are also used to identify specific cells or microorganisms before culture results are available.

If needle aspiration does not provide a good enough sample, the entire lymph node may be removed and sent for culture and other testing.

How to Prepare for the Test

Your health care provider will instruct you on how to prepare for the lymph node sampling .

How the Test will Feel

When local anesthetic is injected, you will feel a prick and a mild stinging sensation. The site will likely be sore for a few days after the test.

Why the Test is Performed

Your doctor may order this test if you have swollen glands and infection is suspected.

Normal Results

A normal result means there was no growth of microorganisms on the lab dish.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results are a sign of a bacterial, fungal, or viral infection.

Risks

Risks may include:

  • Bleeding
  • Infection (in rare cases, the wound may get infected and you may need to take antibiotics)
  • Nerve injury if the biopsy is done on a lymph node close to nerves (the numbness usually goes away in a few months)

Mycobacterial culture

Culture – mycobacterial

Mycobacterial culture is a test to look for the bacteria that cause tuberculosis and similar infections.

How the Test is Performed

A sample of body fluid or tissue is needed. This sample may be taken from the lungs, liver, or bone marrow.

Most often, a sputum sample will be taken . To obtain a sample, you will be asked to cough deeply and spit out the material that comes up from your lungs.

A biopsy or aspiration may also be done.

The sample is sent to a laboratory. There it is placed in a special dish (culture). It is then watched for up to 6 weeks to see if the bacteria grow.

How to Prepare for the Test

Preparation depends on how the test is done. Follow your health care provider’s instructions.

How the Test will Feel

How the test will feel depends on the specific procedure. Your health care provider can discuss this with you before the test.

Why the Test is Performed

Your doctor may order this test if you have signs of tuberculosis or a related infection.

Normal Results

If there is no disease present, there will be no growth of bacteria in the culture medium.

What Abnormal Results Mean

Mycobacterium tuberculosis or similar bacteria is present in the culture.

Risks

Risks depend on the specific biopsy or aspiration being performed.

Nasopharyngeal culture

Culture – nasopharyngeal; Swab for respiratory viruses; Swab for staph carriage

Nasopharyngeal culture is a test that examines a sample of secretions from the uppermost part of the throat, behind the nose, to detect organisms that can cause disease.

How the Test is Performed

You will be asked to cough before the test begins and then tilt your head back. A sterile cotton-tipped swab is gently passed through a nostril and into the nasopharynx. This is the part of the pharynx that covers the roof of the mouth. The swab is quickly rotated and removed. The sample is sent to a laboratory. There, it is placed in a special dish (culture). It is then watched to see if bacteria or other disease-causing organisms grow.

How to Prepare for the Test

No special preparation is needed.

How the Test will Feel

You may have slight discomfort and may gag.

Why the Test is Performed

The test identifies viruses and bacteria that cause upper respiratory tract symptoms. These include:

  • Bordetella pertussis
  • Neisseria meningitidis
  • Staphylococcus aureus
  • Methicillin-resistant Staphylococcus aureus
  • Viral infections such as influenza or respiratory syncytial virus

The culture may be used to help determine which antibiotic is appropriate to treat an infection due to bacteria.

Normal Results

The presence of organisms commonly found in the nasopharynx is normal.

What Abnormal Results Mean

The presence of any disease-causing virus, bacteria, or fungus means these organisms may be causing your infection.

Sometimes, organisms like Staphylococcus aureus can be present without causing disease. This test can help identify resistant strains of this organism (methicillin-resistant Staphylococcus aureus , or MRSA ) so that patients can be isolated when necessary.

Risks

There are no risks with this test.

Pericardial fluid culture

Culture – pericardial fluid

Pericardial fluid culture is a test performed on a sample of fluid from the sac surrounding the heart. It is done to identify organisms that cause infection.

Pericardial fluid gram stain is a related topic.

How the Test is Performed

Some people may have a cardiac monitor placed before the test to check for heart disturbances. Patches called electrodes will be placed on the chest, similar to during an ECG. A chest x-ray or ultrasound may be done before the test.

The skin of the chest will be cleaned with antibacterial soap. A doctor inserts a small needle into the chest between the ribs into the thin sac that surrounds the heart (the pericardium). A small amount of fluid is removed.

You may have an ECG and chest x-ray after the test. Sometimes the pericardial fluid is taken during open heart surgery.

The sample is sent to a lab. Bacteria are grown in samples of the fluid. It can take a few hours to several weeks to get the test results.

How to Prepare for the Test

You will be asked not to eat or drink anything for several hours before the test. You may have a chest x-ray or ultrasound before the test to identify the area of fluid collection.

How the Test Will Feel

You will feel some pressure and discomfort when the needle is inserted into the chest and the fluid is removed. Your doctor should be able to give you pain medicine so that the procedure does not hurt very much.

Why the Test is Performed

Your doctor may order this test if you have signs of a heart sac infection or if you have pericardial effusion .

The test may also be done if you have pericarditis .

Normal Results

A normal result means no infectious organisms are found in the fluid sample.

What Abnormal Results Mean

Abnormal results may be due to an infection of the pericardium. The specific organism causing the infection may be identified. More tests may be needed to determine the most effective treatments.

Risks

Complications are rare but include:

  • Heart or lung puncture
  • Infection

Peritoneal fluid culture

Culture – peritoneal fluid

Peritoneal fluid culture is a laboratory test performed on a sample of peritoneal fluid to detect bacteria or fungi that cause infection ( peritonitis ).

Peritoneal fluid is the fluid from the peritoneal cavity, a space between the wall of the abdomen and the organs inside.

How the Test is Performed

A sample of peritoneal fluid is needed. This sample is obtained using a procedure called an abdominal tap (paracentesis).

A sample of fluid is sent to the laboratory for Gram stain and culture. The sample is checked to see if bacteria grows.

How to Prepare for the Test

Empty your bladder before your abdominal tap procedure.

How the Test will Feel

A small area in your lower abdomen will be cleaned with germ-killing medicine (antiseptic). You will also receive local anesthesia. You will feel pressure as the needle is inserted. If a large amount of fluid is withdrawn, you may feel dizzy or lightheaded.

Why the Test is Performed

The test is done to find out if there is an infection in the peritoneal space.

Normal Results

Peritoneal fluid is a sterile fluid, so normally no bacteria or fungi are present.

What Abnormal Results Mean

The growth of any microorganism, such as bacteria or fungi, from peritoneal fluid is abnormal and indicates peritonitis.

Risks

There is a small risk of the needle puncturing the bowel, bladder, or a blood vessel in the abdomen. This may result in bowel perforation , bleeding, and infection.

Considerations

The diagnosis of peritonitis is based on more than just the peritoneal fluid culture (which may be negative even if you have peritonitis).

Pleural fluid culture

Culture – pleural fluid

Pleural fluid culture is a test that examines a sample of fluid that has collected in the pleural space to see if you have an infection or understand the cause of buildup of fluid in this space. The pleural space is the area between the lining of the outside of the lungs (pleura) and the wall of the chest. When fluid collects in the pleural space, the condition is called pleural effusion .

How the Test is Performed

A procedure called thoracentesis is used to get a sample of pleural fluid. The sample is sent to a laboratory and examined under a microscope for signs of infection. The sample is also placed in a special dish (culture). It is then watched to see if bacteria or any other germs grow.

How to Prepare for the Test

No special preparation is needed before the test. A chest x-ray will be performed before and after the test.

DO NOT cough, breathe deeply, or move during the test to avoid injury to the lung.

How the Test will Feel

For thoracentesis, you sit on the edge of a chair or bed with your head and arms resting on a table. The health care provider cleans the skin around the insertion site. Numbing medicine (anesthetic) is injected into the skin.

A needle is placed through the skin and muscles of the chest wall into the pleural space. As fluid drains into a collection bottle, you may cough a bit. This is because your lung re-expands to fill the space where fluid had been. This sensation lasts for a few hours after the test.

During the test, tell your provider if you have sharp chest pain or shortness of breath.

Why the Test is Performed

Your provider may order this test if you have signs of a certain infection or if a chest x-ray or CT scan of the chest shows you have too much fluid in the space around the lungs.

Normal Results

A normal result means no bacteria or fungi were seen in the test sample.

A normal value is no growth of any bacteria. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may indicate:

  • Empyema (collection of pus in the pleural space)
  • Lung abscess (collection of pus in a lung)
  • Pneumonia
  • Tuberculosis

Risks

Risks of thoracentesis are:

  • Collapsed lung ( pneumothorax )
  • Excessive loss of blood
  • Fluid re-accumulation
  • Infection
  • Pulmonary edema
  • Respiratory distress
  • Serious complications are uncommon

Rectal culture

Culture – rectalRectal culture is a lab test to identify bacteria and other germs in the rectum that can cause gastrointestinal symptoms and disease.

How the Test is Performed

A cotton swab is placed into the rectum. The swab is rotated gently, and removed.

A smear of the swab is placed in culture media to encourage the growth of bacteria and other organisms. The culture is watched for growth.

The organisms can be identified when growth is seen. More tests may be done to determine the best treatment.

How to Prepare for the Test

The health care provider does a rectal exam and collects the specimen.

How the Test will Feel

There may be pressure as the swab is inserted into the rectum. The test is not painful in most cases.

Why the Test is Performed

The test is done if your provider suspects that you have an infection of the rectum, such as gonorrhea . It may also be done instead of a fecal culture if it is not possible to get a specimen of feces.

The rectal culture may also be performed in a hospital or nursing home setting. This test shows if someone carries vancomycin-resistant enterococcus (VRE) in their intestine. This germ can be spread to other patients.

Normal Results

Finding bacteria and other germs that are commonly found in the body is normal.

Normal value ranges may vary slightly among different labs. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may mean you have an infection. This may be:

  • Bacterial infection
  • Parasitic enterocolitis
  • Gonorrhea

Sometimes a culture shows that you are a carrier, but you may not have an infection.

A related condition is proctitis .

Risks

There are no risks.

Gastric tissue biopsy and culture

Culture – gastric tissue; Culture – stomach tissue; Biopsy – gastric tissue; Biopsy – stomach tissue; Upper endoscopy – gastric tissue biopsy; EGD – gastric tissue biopsy

Gastric tissue biopsy is the removal of stomach tissue for examination. A culture is a laboratory test that examines the tissue sample for bacteria and other organisms that can cause disease.

How the Test is Performed

The tissue sample is removed during a procedure called upper endoscopy (or EGD) . It is done with a flexible tube with a small camera (flexible endoscope) at the end. The scope is inserted down the throat into the stomach.

The health care provider sends the tissue sample to a laboratory where it is examined for signs of cancer, certain infections, or other problems.

How to Prepare for the Test

Follow instructions on how to prepare for the procedure. You will likely be asked not to eat or drink anything for 6 to 12 hours before the procedure.

How the Test will Feel

Your provider will tell you what to expect during the procedure.

Why the Test is Performed

This test may be done to diagnose a stomach ulcer or the cause of other stomach symptoms. These symptoms may include:

  • Loss of appetite or weight loss
  • Nausea and vomiting
  • Pain in the upper part of the belly
  • Black stools
  • Vomiting blood or coffee ground-like material

A gastric tissue biopsy and culture can help detect:

  • Cancer
  • Infections, most commonly Helicobacter pylori , the bacteria that can cause stomach ulcers

Normal Results

A gastric tissue biopsy is normal if it does not show cancer, other damage to the lining of the stomach, or signs of organisms that cause infection.

A gastric tissue culture may be considered normal if it does not show certain bacteria. Stomach acids normally prevent too much bacteria from growing.

What Abnormal Results Mean

Abnormal results may be due to:

  • Stomach (gastric) cancer
  • Gastritis , when the lining of the stomach becomes inflamed or swollen
  • Helicobacter pylori infection

Risks

Your provider can discuss the risks of the upper endoscopy procedure with you.

Fecal culture

Stool culture; Culture – stool; Gastroenteritis fecal culture

A fecal culture is a lab test to find organisms in the stool (feces) that can cause gastrointestinal symptoms and disease.

How the Test is Performed

A stool sample is needed.

There are many ways to collect the sample.

You can collect the sample:

  • On plastic wrap. Place the wrap loosely over the toilet bowl so that it is held in place by the toilet seat. Put the sample in a clean container given to you by your health care provider.
  • In a test kit that supplies a special toilet tissue. Put it in a clean container given to you by your provider.

Do not mix urine, water, or toilet tissue with the sample.

For children wearing diapers:

  • Line the diaper with plastic wrap.
  • Position the plastic wrap so that it will prevent urine and stool from mixing. This will provide a better sample.

Return the sample to the laboratory as soon as possible. Do not include toilet paper or urine in the specimen.

In the lab, a technician places a sample of the specimen in a special dish. The dish is then filled with a gel that boosts the growth of bacteria or other germs. If there is growth, the germs are identified. The lab technician may also do more tests to determine the best treatment.

How to Prepare for the Test

You will get a collection container for the stool specimen.

How the Test will Feel

There is no discomfort.

Why the Test is Performed

The test is performed when your health care provider suspects that you may have a gastrointestinal infection. It may be done if you have severe diarrhea that does not go away or that keeps coming back.

Normal Results

There are no abnormal bacteria or other organisms in the sample.

Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may mean you have an intestinal infection .

Risks

There are no risks.

Considerations

Often other stool tests are done in addition to the culture, such as:

  • Gram stain of stool
  • Fecal smear
  • Stool ova and parasites exam

Throat swab culture

Throat culture and sensitivity; Culture – throat

A throat swab culture is a laboratory test that is done to identify germs that may cause infection in the throat. It is most often used to diagnose strep throat .

How the Test is Performed

You will be asked to tilt your head back and open your mouth wide. Your health care provider will rub a sterile cotton swab along the back of your throat near your tonsils. You will need to resist gagging and closing your mouth while the swab touches this area.

Your provider may need to scrape the back of your throat with the swab several times. This helps improve the chances of detecting bacteria.

How to Prepare for the Test

DO NOT use antiseptic mouthwash before this test.

How the Test will Feel

Your throat may be sore when this test is done. You may feel like gagging when the back of your throat is touched with the swab, but the test only lasts a few seconds.

Why the Test is Performed

This test is done when a throat infection is suspected, particularly strep throat. A throat culture can also help your provider determine which antibiotic will work best for you.

Normal Results

A normal or negative result means no bacteria or other germs that may cause a sore throat were found.

What Abnormal Results Mean

An abnormal or positive result means bacteria or other germs that can cause a sore throat were seen on the throat swab.

Risks

This test is safe and easy to tolerate. In very few people, the sensation of gagging may lead to an urge to vomit or cough.

Urine culture – catheterized specimen

Culture – urine – catheterized specimen; Urine culture – catheterization; Catheterized urine specimen culture

Catheterized specimen urine culture is a laboratory test that looks for germs in a urine sample.

How the Test is Performed

This test requires a urine sample. The sample is taken by placing a thin rubber tube (called a catheter) through the urethra into the bladder. A nurse or a trained technician may do this.

First, the area around the opening of the urethra is thoroughly washed with a germ-killing (antiseptic) solution. The tube is inserted into the urethra. The urine drains into a sterile container, and the catheter is removed.

Rarely, the health care provider may choose to collect a urine sample by inserting a needle directly into the bladder from the abdominal wall and draining the urine. However, this is usually only done in infants or to immediately screen for bacterial infection.

The urine is sent to a laboratory. Tests are done to determine if there are germs in the urine sample. Other tests may be done to determine the best medicine to fight the germs.

How to Prepare for the Test

Do not urinate for at least 1 hour before the test. If you don’t have the urge to urinate, you may be instructed to drink a glass of water 15 to 20 minutes before the test. Otherwise, there is no preparation for the test.

How the Test will Feel

There is some discomfort. As the catheter is inserted, you may feel pressure. If you have a urinary tract infection , you may have some pain when the catheter is inserted.

Why the Test is Performed

The test is done:

  • To get a sterile urine sample in a person who cannot urinate on their own
  • If you might have a urinary tract infection
  • If you cannot empty your bladder (urinary retention)

Normal Results

Normal values depend on the test being performed. Normal results are reported as “no growth” and are a sign that there is no infection.

What Abnormal Results Mean

A “positive” or abnormal test means germs, such as bacteria or yeast, are found in the urine sample. This likely means that you have a urinary tract infection or a bladder infection. If there is only a small amount of germs, your health care provider may not recommend treatment.

Sometimes, bacteria that do not cause urinary tract infections may be found in the culture. This is called a contaminant. You may not need to be treated.

People who have a urinary catheter in all of the time may have bacteria in their urine sample, but it does not cause a true infection. This is called being colonized.

Risks

Risks include:

  • Perforation (hole) in the urethra or bladder from the catheter
  • Infection

Urethral discharge culture

Culture of urethral discharge; Genital exudate culture; Culture – genital discharge or exudate

Urethral discharge culture is a laboratory test done on men and boys. This test is used to identify germs in the urethra that may be causing  urethritis . The urethra is the tube that drains urine from the bladder.

How the Test is Performed

The health care provider uses sterile cotton or gauze to clean the opening of the urethra at the tip of the penis. To collect the sample, a cotton swab is then gently inserted about 3/4 inch (2 centimeters) into the urethra and turned. To get a good sample, the test should be done at least 2 hours after urinating.

The sample is sent to a lab. There, it is placed in a special dish (culture). It is then watched to see if bacteria or any other germs grow.

How to Prepare for the Test

Do NOT urinate for 1 hour before the test. Urinating washes away some of the germs needed for accurate test results.

How the Test will Feel

There is usually some discomfort from swabbing the urethra.

Why the Test is Performed

The provider often orders the test when there is a discharge from the urethra. This test can detect sexually transmitted infections (STIs), such as gonorrhea and chlamydia .

Normal Results

A negative culture, or no growth appearing in the culture, is normal.

What Abnormal Results Mean

Abnormal results can be a sign of infection in the genital tract. These infections can include gonorrhea or chlamydia.

Risks

Fainting may occur when the swab is introduced into the urethra. This is due to stimulation of the vagus nerve. Other risks include infection or bleeding.

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