What Is a Sputum Stain for Mycobacteria?
A sputum stain for Mycobacteria
is a laboratory test performed on a sample of your sputum, or phlegm. It’s also known as an
acid-fast bacillus (AFB) stain or a tuberculosis (TB) smear. A doctor typically
orders the test to determine if a person has tuberculosis (TB) or another type of mycobacterial
If you’re already taking medication for TB or another
mycobacterial infection, your doctor might order the test to find out if your
medication is working.
Why the Test Is Ordered
Your doctor will order this test if they think you have a
Mycobacteria are a
type of microorganism with nearly 100 known species. The most common type is Mycobacterium
tuberculosis, which causes
TB. The general symptoms of TB include:
- coughing up blood or mucus
- a lack of appetite
- weight loss
- a fever
- night sweats
Another fairly common type of this bacteria is Mycobacterium
leprae, which causes leprosy. The symptoms of leprosy include:
- skin discoloration
- skin lesions
- skin nodules
- skin plaques
- thickened skin
- nasal congestion
Except for the two microorganisms that cause TB and leprosy,
most Mycobacteria exist in the water
and soil everywhere in the world. These are called nontuberculous mycobacteria
NTM live in:
- city water
- hot tubs
- swimming pools
- yard soil
Their tough, waxy cell wall makes them resistant to
Although NTM are everywhere, most people aren’t affected.
People with immunity problems, such as AIDS, are vulnerable to infection. Some
people can have an infection with no symptoms at all. Other people have
infections that cause lung symptoms similar to TB.
Medicines can treat these infections, but it often takes more
than one medicine to cure them.
How to Prepare for Self-Collection
The night before the test, drink lots of fluids, such as water
or tea. This will help your body make more sputum overnight. Collecting your
sputum in the morning makes the test more accurate. More bacteria are present
first thing in the morning.
How to Collect a Sample of Your Sputum
Either you or your doctor will collect the sputum.
If you’re very sick, you may already be in the hospital. If so,
a healthcare provider will help you cough up sputum to send to the laboratory
for the test. If you have trouble coughing up sputum on your own, they may have
you breathe steam.
If you’re sick at home, you’ll need to collect the sputum
Keep in mind that sputum from deep inside your lungs isn’t the
same as saliva. Sputum is mucus, and it’s usually colored and thick in consistency,
especially when there’s an infection in your lungs. Saliva comes
from your mouth. It’s clear and thin.
Plan to collect sputum the first thing in the morning. This
makes the test more accurate. Don’t eat or drink anything in the morning before collecting your sample. Your doctor will give you sample cup, which is sterile. Don’t open the cup until you’re
ready to collect the sample.
To collect a sputum sample, you should do the following:
- Brush your teeth and rinse your mouth without
using antiseptic mouthwash.
- Take a couple of long, deep breaths.
- Breathe deeply again and cough hard until sputum
- Spit out the sputum into the sample cup.
- Keep coughing up sputum until the cup is filled
to the marker, which is approximately 1 teaspoon.
- Screw on the cup lid, and wash and dry the
outside of it.
- Write your name, your date of birth, and the
date of collection on the cup label.
Take the sample to the clinic or laboratory, as instructed. The
sample can be refrigerated for up to 24 hours if needed. Don’t freeze it or
store it at room temperature.
If you can’t cough up sputum, try breathing the steam from
boiling water, or take a hot, steamy shower. The sputum must come from deep
inside your lungs for the test to be accurate.
If you still cannot cough up sputum, your doctor will do a
bronchoscopy to collect sputum directly from your lungs.
What Is a Bronchoscopy?
Bronchoscopy is a simple procedure that takes about 30 to
60 minutes. It’s often done in the doctor’s office while the person is awake.
Don’t take medicines that thin your blood the day before your
bronchoscopy. These medicines include:
- ibuprofen (Motrin, Advil)
- naproxen (Aleve)
You may take acetaminophen (Tylenol)
if needed for pain. You’ll also be asked not to eat or drink anything the night
before the procedure.
Bronchoscopy is performed as follows:
- A local anesthetic will be sprayed into your
nose and throat to numb them.
- You might be given a sedative to help you relax or
medication to put you to sleep.
- General anesthesia isn’t usually needed for
- The bronchoscope is a soft, small tube
with a light and magnifying glass on the end. Your doctor feeds the scope
through your nose or mouth and into your lungs.
- Your doctor can see into your lungs using a
magnifying glass, and they can use the scope to remove a sample of your sputum.
- You’ll have a nurse with you during and after
the procedure until you’re fully awake.
- For safety, you should have someone else drive
Sputum Stain Test
Your sputum specimen will be spread on a microscope slide. A
staining dye is added to the cells of the specimen and then washed in an acid
solution. The cells are then examined under a microscope.
If the cells retain the stain, this means mycobacterium are
present. Mycobacteria are usually acid-fast,
which means they hold onto the dye when washed in an acid solution.
A culture is another kind of test that may be done. The
sputum specimen is placed into a culture medium, which contains nutrients. The
specimen is allowed to grow at room temperature for several days. This makes it
possible to see a greater number of bacteria cells to confirm the results.
There are no risks associated with collecting a sputum sample
yourself. You might feel light-headed when coughing deeply. Rare risks of
- an allergic reaction to sedatives
- an infection
- bronchial spasms, which involve sudden
clenching of the muscles in the bronchioles
- irregular heart rhythms
A pneumothorax is
another rare risk. It involves a tearing in the lung that results
in a small amount of air being released between the lung and chest wall. If
it’s small, it usually fixes itself.
Results of the Test
If your test results are normal, or negative, this means no
mycobacterial organisms were found.
If the test is abnormal, it means the stain is positive for one
of the following organisms:
- M. tuberculosis
- M. leprae
- nontuberculous bacteria
- other acid-fast bacteria
Your doctor will advise you on your results. If you need
treatment, they’ll tell you about your best options.