Laboratory diagnosis of tuberculosis by sputum microscopy

Which staining method is used for detection of Mycobacterium tuberculosis?

Sputum smear microscopy using the ubiquitous Ziehl-Neelsen (ZN) stain , the primary diagnostic strategy for active tuberculosis (TB) worldwide that is recommended by the World Health Organization (WHO),1 is constrained by its reliance on human skill and time-intensive nature.May 5, 2016

In our suspension studies (EN 14348), chlorine-based disinfectant (Chlor-Clean) showed activity against both strains of mycobacteria M.

Higher concentrations (1,000 ppm) of chlorine are required to kill M. tuberculosis using the Association of Official Analytical Chemists (AOAC) tuberculocidal test 73. A concentration of 100 ppm will kill ≥99.9% of B. atrophaeus spores within 5 minutes 541, 542 and destroy mycotic agents in <1 hour 329.

Mycobacterium tuberculosis is extraordinarily sensitive to killing by a vitamin C-induced Fenton reaction - PMC. The . gov means it's official.

Which of the following method is used for the detection of Mycobacterium tuberculosis Mcq?

The TST is used to determine if a person is infected with M. tuberculosis. In this test, a substance called purified protein derivative (PPD), which is derived from tuberculin, is injected under the skin.

PCR methods allow direct identification of Mycobacterium tuberculosis complex and can detects less than 10 bacteria in a clinical specimen.May 10, 2018

Mycobacteria are Gram-positive , catalase positive, non-motile, non-spore forming rod-shaped bacteria (0.2–0.6 μm wide and 1.0–10 μm long).

Gram staining is a useful technique for detecting bacteria but is highly questionable in detecting Mycobacterium tuberculosis . Its detection generally requires special staining, such as Ziehl-Neelsen staining.

What is the principle of ZN stain?

PURPOSE: Used in the demonstration of acid-fast bacteria belonging to the genus 'mycobacterium', which include the causative agent for tuberculosis. PRINCIPLE: The lipoid capsule of the acid-fast organism takes up carbol- fuchsin and resists decolorization with a dilute acid rinse .

Microscopic examination of clinical samples for acid-fast bacilli using the Ziehl-Neelsen (ZN) stain has been a standard diagnostic tool and is used globally for rapid TB diagnosis . Microscopy can detect 60% to 70% of culture-positive samples with a lower limit of detection of 5 × 103 organisms/mL.

Acid-fast organisms are highly resistant to disinfectants and dry conditions. Because the cell wall is so resistant to most compounds , acid-fast organisms require a special staining technique.

Mycobacterium and its close relatives. Mycobacteria are Gram-positive, acid-fast and (G + C) rich (62 – 70%); they are aerobic and rod shaped and mycolic acids are components of their cell walls (for review see Wayne and Kubica, 1986).

What Gram stain is Mycobacterium tuberculosis?

tuberculosis is an acid-fast bacterium (AFB), and is therefore, undetectable when stained using a Gram stain technique . However, using the Smithwick method, which employs acridine orange as the specific dye, the M. tuberculosis bacteria glow yellow under ultraviolet light microscopy.

Following growth in culture, molecular technologies such as nucleic acid hybridization probes, MALDI-TOF MS, and DNA sequencing may be used for definitive species identification.

The Mantoux tuberculin skin test (TST) or the TB blood test can be used to test for M. tuberculosis infection. Additional tests are required to confirm TB disease. The Mantoux tuberculin skin test is performed by injecting a small amount of fluid called tuberculin into the skin in the lower part of the arm.

In fact, it is very difficult to stain any mycobacterium . There is one specific technique to stain mycobacterium: the Ziehl-Neelsen stain, named after the two German doctors who first described it. When stained with a Ziehl-Neelsen stain, the mycolic acids take on the color quickly and retain them inside the bacillus.

Is Mycobacterium Gram-positive or acid-fast?

Most mycobacteria are not pathogenic, and are readily isolated from the environment Daniel (1992). These bacteria are gram-positive, aerobic, non-sporulating, non-motile, and often pleomorphic. They are typically smaller than other bacteria. Mycobacteria are acid-fast because of lipid-rich cell envelope.

Low levels of penicillin and nalidixic acid are also present in LJ medium to inhibit growth of Gram-positive and Gram-negative bacteria, to limit growth to Mycobacterium species only. Presence of malachite green in the medium inhibits most other bacteria. It is disinfected and solidified by a process of inspissation .

tuberculosis mycobacteria. We found that acetic acid (vinegar) efficiently kills M. tuberculosis after 30 min of exposure to a 6% acetic acid solution. The activity is not due to pH alone, and propionic acid also appears to be bactericidal.

The conventional culture method for Mycobacterium tuberculosis is a more sensitive technique by which to detect TB compared with AFB smears, but, due to the slow growth of the organism, sputum cultures take 4–6 weeks to become positive on solid media and 10–21 days in liquid media.Jun 3, 2019

How is M. tuberculosis identified?

Tests such as an acid-fast-bacilli (AFB) smear, culture, and nucleic acid amplification tests (NAATs) indicate the presence of MTB. Additional laboratory testing is required to identify drug resistance or susceptibility. A definitive diagnosis of TB requires positive culture results.

When looking at the smears for TB, it is stained using an acid-fast stain . These acid-fast organisms like Mycobacterium contain large amounts of lipid substances within their cell walls called mycolic acids. These acids resist staining by ordinary methods such as a Gram stain.

The diagnosis of mycobacterial infection depends on the Ziehl-Neelsen (ZN) stain , which detects mycobacteria because of their characteristic acid-fast cell wall composition and structure.