test Details

Pneumonia, Abscesses, Endocarditis, Food poisoning, Meningitis, Urinary tract infection

Bacterias are majorly responsible for infections in our bodies. There are mainly two types of infection-causing bacteria- Gram-positive bacteria and Gram-negative bacteria.

They are further classified as cocci and bacilli, depending on their shape. The cocci bacteria are spherical in shape, and the bacilli bacteria are rod-shaped. They can cause Gram-positive cocci- Skin infection, Toxic shock syndrome, Pneumonia(lung infection), Gram-negative cocci- Gonorrhea(sexually transmitted disease), Meningitis(infection in brain membranes), Gram-positive bacilli- Food poisoning, Skin infections, Gram-negative bacilli- Urinary tract infections.

The Gram stain test is used to find out the presence of bacterial infection. It also tells whether it is because of gram-positive or gram-negative bacteria. The bacteria can be detected in blood, sputum, or urine depending upon the area of infection.

The gram stain test is a laboratory test. It uses a series of stains to identify the bacteria. The sample that is collected from the patient is applied on a glass slide, and Gram stains are added to it. The bacteria present in the sample absorb these stains. They turn purple, blue, pink, or red.

The bacteria that turn purple or blue are gram-positive bacteria, and those that turn pink or red are gram-negative bacteria. The gram stain test is a preliminary test; it may require further tests like a bacteria culture test to know about the bacteria that has caused the infection and confirm the diagnosis.

Symptoms including fever, headache, nausea, vomiting, loose motion, cough, sore throat, pain or swelling in the neck, and fatigue are commonly seen during bacterial infection. Other symptoms are also seen depending on the body part which is infected. You should never ignore a bacterial infection as it spreads quickly. The results of the gram stain test will guide the consulting physician with the medications and treatment plan.

India is a big country. Every year many people suffer from bacterial infections. In recent years, there has been a significant improvement in the prevention, diagnosis and treatment of bacterial infection in India. But still, a long way to go. The unhygienic environment, contaminated food and water, bacterial resistance to certain medicines and emerging new infections are big concerns for India.

Other names of Gram Stain Test

• Faeces - Gram stain
• Stool - Gram stain
• Urethral discharge - Gram stain
• Joint fluid - Gram stain
• Sputum - Gram stain
• Gram stain of urethral discharge
• Pericardial fluid - Gram stain
• Pleural fluid - Gram stain
• Gram stain of the cervix
• Skin lesion - Gram stain
• Gram stain of tissue biopsy
• Gram stain of skin lesion

What does the gram stain test detect, and who is this prescribed for?

The gram stain test detects the presence or absence of disease-causing bacteria and differentiates the type of bacteria- Gram-positive bacteria or Gram-negative bacteria. It also tells about the cocci and bacilli bacteria.

If a person is experiencing the following conditions, the consulting physician may prescribe the gram stain:

• Cough from a long time that may have a foul odour or different colour
• Vomiting, nausea, loose motions and pain in the stomach
• Sore throat
• Pain and swelling in the neck region
• Fever
• Fatigue
• Headache
• Burning sensation while urinating
•  Intestinal infection or illness
• Unexplained swelling or joint pain
• Painful skin wound with pus

Symptoms may vary depending on the location where the infection has occurred. For people with such complaints, the gram stain test is prescribed by the consulting physician to detect bacterial infection.

Some disease conditions for which a gram stain test can be prescribed are

• Pneumonia
• Gonorrhoea
• Sexually transmitted diseases (STDs)
• Endocarditis
• Food poisoning
• Lung infection(in space around the lungs)
• Heart infection (in the pericardium)
• Meningitis
• Urinary tract infection
• Abscess
• Methicillin-resistant Staphylococcus aureus infection (MRSA)

After getting the results of the Gram stain test, the doctor will prescribe the medications. The gram stain test is applicable to males and females, both adults and children. If you are already taking antibiotics, it may affect test results. Inform your doctor about all the medicines you are taking.

In the positive gram stain result,

 The gram stain test is safe during pregnancy, but antibiotics should be taken as per the advice of the consulting doctor.

The interpretation of the Gram stain test is the presence or absence of the bacteria on the site of infection. If the test result is negative, it shows that there are no bacteria in the sample. If the test result is positive, it shows the presence of bacteria or fungus in the sample. A separate culture test is required to test whether it is a fungus or bacteria.

The positive gram stain also interprets the type of bacteria depending upon the shape and colour of the bacteria after the test:

• Purple/blue colour and round-shaped: Gram-positive cocci
• Pink/red colour and round-shaped: Gram-negative cocci
• Purple/blue colour and rod-shaped: Gram-positive bacilli
• Pink/red colour and rod-shaped: Gram-negative bacilli

The gram stain test also interprets the size, arrangement and relative quantity of bacteria, and the presence of red and white blood cells in some cases. After interpreting the result, doctors will prescribe antibiotics and further tests to know the cause of the infection.

The sample is collected from the site of infection or wound. It can be blood, stool, urine, pus, cerebrospinal fluid (CSF), or sputum.

Test Preparation

The gram stain test may require different types of samples according to the body part where it is present. The most common method for collecting a sample is-

• Pus sample: The healthcare practitioner will collect the sample from the wound site using a clean, sterile swab.
• Blood sample: A needle is used to collect the blood from the prominent vein of your forearm.
• Urine sample: The healthcare practitioner will provide you with a sterile cup to collect the urine in it. Follow the instructions given by them carefully.
• Sputum sample: You are asked to cough sputum into a sterile cup.
• Throat sample: The healthcare practitioner will insert a special swab into your mouth and collect the sample from the throat.

The procedure is usually painless and does not require more than 5 minutes. The collected sample is sent to the laboratory, where professionals examine the sample under a microscope.

Test inclusions: What parameters are included?

The parameters of the Gram stain test are

• Presence of bacteria
• Type of bacteria: gram-positive or gram-negative and cocci(round-shaped) or bacilli(rod-shaped)
• Size, relative arrangement and quantity of bacteria in some cases
• Presence or absence of red blood cells and white blood cells in the sample
• Presence or absence of Fungi like yeast

The gram stain results show these parameters with the help of test results, signs and symptoms in the person, the doctor prescribes the treatment.

This test cannot tell us about the bacteria that caused the infection. The doctor may need other tests for an exact diagnosis. The results will only show that bacteria is present. At times, it can create confusion as the test does not differentiate between the healthy normal bacteria present in the body and disease-causing bacteria.

How frequently should you take this test?

The consulting physician will prescribe the gram stain test following the symptoms of bacterial infection. The test result will help the doctor with medications and also check whether there is a need for other tests. The doctor may repeat the test if required.