Is AFB a Gram stain?
Acid-fast bacteria are gram-positive in terms of structure because they contain peptidoglycan in the cell wall. However, they stain poorly with Gram stain procedure, appearing weakly Gram-positive.
Why acid fast bacteria Cannot be Gram stained?
Mycobacteria are “Acid Fast” 1. They cannot be stained by the Gram stain because of their high lipid content.
How do you collect sputum for AFB test?
Take a very deep breath and hold the air for 5 seconds. Slowly breathe out. Take another deep breath and cough hard until some sputum comes up into your mouth. Spit the sputum into the plastic cup.
Is AFB gram-positive?
Acid-fast bacteria are gram-positive, but in addition to peptidoglycan, the outer membrane or envelope of the acid-fast cell wall of contains large amounts of glycolipids, especially mycolic acids that in the genus Mycobacterium, make up approximately 60% of the acid-fast cell wall (Figure 2.3C.
What is difference between gram-positive and Gram negative bacteria?
Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane whilst Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane.
What does a Gram stain test for?
A Gram stain is a test that checks for bacteria at the site of a suspected infection such as the throat, lungs, genitals, or in skin wounds. Gram stains may also be used to check for bacteria in certain body fluids, such as blood or urine.
Is AFB gram positive?
When is AFB staining performed?
When Your Doctor May Order an AFB Stain If you have symptoms of a lung infection, your doctor may use an AFB stain to explore the cause. These symptoms often include a chronic or long-lasting cough, coughing up blood, significant weight loss, fever, chills, and fatigue. You’re high-risk or positive for TB.
What is a positive AFB smear?
If your AFB smear was positive, it means you probably have TB or other infection, but an AFB culture is needed confirm the diagnosis. Culture results can take several weeks, so your provider may decide to treat your infection in the meantime.
What is the Colour of sputum for TB?
Tuberculosis (TB) If someone has TB, they may cough up green or bloody phlegm.
What is the AFB smear microscopy module?
This is the AFB Smear Microscopy Module. The goal of this module is to take an in- depth look at the standards of practice in the Mycobacteriology Lab for preparing AFB smears, examining AFB smears, recording smear results, and interpreting those smear results. 1.2 Terminology Notes: First, let’s look at some terminology.
What are the limitations of Air Force base microscopy?
There are some limitations of AFB Microscopy. Smears don’t distinguish between viable and dead organisms. Follow-up specimens from patients on treatment may be smear positive and yet, culture negative. Smears have limited sensitivity. You need a high bacterial load 5,000-10,000 organisms are required for detection on the smear.
What does a positive AFB smear result mean?
All types of specimens can be evaluated, including respiratory specimens, tissue, bodily fluids, etc. Positive AFB smear results provide a first indication of mycobacterial infection, and TB disease. Ultimately, the smear is a great screening tool but it must be accompanied by additional testing including culture for a conformation of diagnosis.
What is the principle of AFB staining?
Principle of AFB Staining Presence of higher alcohol, glycerol, fatty acid and especially mycolic acid in the cell wall have been found responsible for keeping the acid-fast property of bacteria. Therefore, AFB staining is useful for Mycobacterium tuberculosis, an etiological agent of tuberculosis.