What is Mycobacterium leprae?
Mycobacterium leprae is the aetiologic agent of leprosy affecting the skin and peripheral nerves. The infection is currently found in over 100 countries often located in high-burden areas against a low-burden background of cases.
Is Mycobacterium tuberculosis Gram positive or negative?
This coating makes the cells impervious to Gram staining, and as a result, M. tuberculosis can appear either Gram-negative or Gram-positive. Beside above, how do I identify Mycobacterium leprae? leprae.
What is the morphology of Mycoplasma leprae?
Due to its thick waxy coating, M. leprae stains with a carbol fuchsin rather than with the traditional Gram stain. Efforts to culture the bacteria in vivo are still unsuccessful. Optical microscopy shows M. leprae in clumps, rounded masses, or in groups of bacilli side by side, and ranging from 1–8 μm in length and 0.2–0.5 μm in diameter.
How does Mycobacterium leprae cause sensory mononeuritis multiplex?
Mycobacterium leprae infects Schwann cells by binding to α-dystroglycan, causing sensory mononeuritis multiplex, a major complication of leprosy. Clostridium botulinum secretes a toxin that consists of a heavy chain and a light chain.
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Is Mycobacterium Gram-positive?
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). The colony morphology of mycobacteria varies with some species growing as rough or smooth colonies.
Which type of bacteria is Mycobacterium leprae?
M. leprae is an intracellular, pleomorphic, acid-fast, pathogenic bacterium. It is an aerobic bacillus (rod-shaped bacterium) with parallel sides and round ends, surrounded by the characteristic waxy coating unique to mycobacteria. In size and shape, it closely resembles Mycobacterium tuberculosis.
Is Mycobacterium tuberculosis Gram negative or positive?
tuberculosis belongs to the high G+C Gram-positive bacteria that form a monophyletic group with the low G+C Gram-positive bacteria such as Bacillus subtilis. Some analyses indicate no particular relationship between these two groups.
How is Mycobacterium leprae identified?
leprae can be rapidly detected and identified using PCR-RFLP. The new PCR/restriction enzyme pattern would help to arrive at the differentiation between leprosy and other mycobacterial infectious cases. It also had shown an advantage to detect the clinical samples from paraffin-embedded skin biopsy and fresh tissues.
What is the difference between Mycobacterium tuberculosis and leprae?
Mycobacterium tuberculosis is cultivable; Myco- bacterium leprae is not. M leprae infects peripheral nerves; M tuberculosis does not. Untreated tuber- culosis has a high mortality; untreated leprosy has a high disability rate due to peripheral neuropathy.
How can you distinguish Mycobacterium tuberculosis and Mycobacterium leprae?
Major differences among these two bacteria were seen regarding the cell size and thickness of the PG layer. M. leprae had a smaller cell size and a thinner PG layer than M. tuberculosis.
Why Mycobacterium is not Gram stain?
Mycobacteria are "Acid Fast" They cannot be stained by the Gram stain because of their high lipid content.
How can you tell the difference between Gram-positive and Gram negative bacteria?
The gram-positive bacteria retain the crystal violet colour and stain purple whereas the gram-negative bacteria lose crystal violet and stain red. Thus, the two types of bacteria are distinguished by gram staining. Gram-negative bacteria are more resistant to antibodies because their cell wall is impenetrable.
Is Mycobacterium a rod or cocci?
Mycobacteria are immobile, slow-growing rod-shaped, gram-positive bacteria with high genomic G+C content (61-71%). Due to their special staining characteristics under the microscope, which is mediated by mycolic acid in the cell wall, they are called acid-fast.
What type of host cell does Mycobacterium leprae typically infect?
M. leprae primarily invades Schwann cells (SCs) in the peripheral nerves leading to nerve damage and the development of disabilities [2].
Is Mycobacterium leprae motile?
Mycobacterium leprae is an acid fast bacillus, non motile, non spore forming, straight or slightly curved bacterium, responsible for causing leprosy.
Why is Mycobacterium leprae difficult to culture?
leprae to rely on the host cell to survive. The bacteria needs an extremely specific environment to thrive in. It is extremely difficult to culture Mycobacterium leprae. All attempts to create a medium that the bacteria are able to grow in has failed.
What is the spectrum of Mycobacterium leprae?
Mycobacterium leprae causes granulomatous disease, anesthetic skin lesions, and nerve damage immune reactions. Spectrum of disease runs from tuberculoid leprosy with few bacilli and a granulomatous response to many organisms with little granulomatous response as lepromatous leprosy.
How is Mycobacterium leprae transmitted?
Mycobacterium leprae is most likely transmitted by contact with patients who shed microorganisms in nasal secretions and lesion exudates. It primarily affects the nerves and the skin, frequently leading to stigmatizing deformities.
What is the aetiologic agent of leprosy?
Mycobacterium leprae. Mycobacterium leprae is the aetiologic agent of leprosy affecting the skin and peripheral nerves. The infection is currently found in over 100 countries often located in high-burden areas against a low-burden background of cases.
Why is M. leprae considered a metabolic restriction?
The genome of M. leprae predicts severe metabolic restrictions due to a multitude of gene disruptions and deletions. Because of the inability to culture the M. leprae in vitro, animal models continue to provide a basis for testing new drugs and vaccines and offer insight into basic mechanisms of pathogenesis.
Why is lepromatous leprosy a cellular disease?
Patients with lepromatous leprosy have disseminated infection associated with poor cellular immune responses. They often develop major ocular complications and blindness. The mechanisms which protect the front surface of the eye are compromised because of damage to the facial and trigeminal nerves caused by M. leprae.
When was the genome of M. leprae sequenced?
In 2001, the genome of M. leprae was sequenced. The organism appears to have undergone extensive reductive evolution with considerable downsizing of its genome compared with Mycobacterium tuberculosis. Almost half of the genome is occupied by pseudogenes. View chapter Purchase book. Read full chapter.
Which bacillus is known to selectively invade human peripheral nervous tissue?
Mycobacterium leprae. Mycobacter ium leprae is the only bacillus known to selectively invade human peripheral nervous tissue, where an inflammatory process leads to nerve compression and ultimately nerve damage. From: International Encyclopedia of Public Health (Second Edition), 2017. Download as PDF.
What is the binomial name for Mycobacterium leprae?
Hansen, 1874. The manifestation of Mycobacterium leprae ( leprosy) in human flesh as Tubercular leprosy. Mycobacterium leprae is a bacterium that causes leprosy, also known as " Hansen’s disease", which is a chronic infectious disease that damages the peripheral nerves and targets the skin, eyes, nose, ...
How many genes are in M. leprae?
leprae and M. tuberculosis have been lost in the M. leprae genome. 1500 genes are still common to both M. leprae and M. tuberculosis .
How big is M. leprae?
Optical microscopy shows M. leprae in clumps, rounded masses, or in groups of bacilli side by side, and ranging from 1–8 μm in length and 0.2–0.5 μm in diameter. The organism has been successfully grown on an artificial cell culture medium on a very limited basis by researcher Arvind Dhople. This can be used as a diagnostic test for the presence of bacilli in body lesions of suspected leprosy patients. The difficulty in culturing the organism appears to be because it is an obligate intracellular parasite that lacks many necessary genes for independent survival. The complex and unique cell wall that makes members of the genus Mycobacterium difficult to destroy is apparently also the reason for the extremely slow replication rate. Virulence factors include a waxy exterior coating, formed by the production of mycolic acids unique to Mycobacterium .
Why is mycobacterium replication so slow?
The complex and unique cell wall that makes members of the genus Mycobacterium difficult to destroy is apparently also the reason for the extremely slow replication rate. Virulence factors include a waxy exterior coating, formed by the production of mycolic acids unique to Mycobacterium .
What are the symptoms of leprosy?
The diagnosis of leprosy is primarily a clinical one. In one Ethiopian study, the following criteria had a sensitivity of 94% with a positive predictive value of 98% in diagnosing leprosy. Diagnosis was based on one or more of three signs: 1 Hypopigmented or reddish skin patches with definite loss of sensation 2 Thickened peripheral nerves 3 Acid-fast bacilli on skin smears or biopsy material
How long does it take for a leprae to go away?
The symptoms of M. leprae, also known as leprosy, are unattractive skin sores that are pale in color, lumps or bumps that do not go away after several weeks or months, nerve damage which can lead to complications with the ability to sense feeling in the arms and legs as well as muscle weakness.
What is the best treatment for M. leprae?
Multidrug therapy (MDT) uses combinations of antibiotics that kill M. leprae including: dapsone, rifampin, clofazamine, fluoroquinolones, azithromycin, and minocycline. Antibiotics must be taken regularly until treatment is complete due to the fact M. leprae has the ability to grow back.
Is the genome sequence of M. tuberculosis genome based?
tuberculosis allows us to reexamine this issue from genomic perspectives, as genome-based phylogenies may be more representative of the evolutionary history of whole organisms than molecular trees.
Is M. tuberculosis Gram positive or negative?
In the genome tree constructed based on conserved gene content, M. tuberculosis is more related to Gram-negative than to Gram-positive bacteria as reflected by the evolutionary distance between nearest ancestral units.
Is M. tuberculosis a monophyletic group?
In the standard reference of bacterial phylogeny based on 16S ribosomal RNA sequence comparison, M. tuberculosis belongs to the high G+C Gram-positive bacteria that form a monophyletic group with the low G+C Gram-positive bacteria such as Bacillus subtilis.
Overview
Mycobacterium leprae is a bacterium that causes Hansen’s disease (leprosy), which is a chronic infectious disease that damages the peripheral nerves and targets the skin, eyes, nose, and muscles. It has also been known as the leprosy bacillus or Hansen's bacillus. Leprosy can occur at all ages from infancy to elderly, but is curable in which treatments can avert disabilities. It was discove…
Microbiology
M. leprae is an intracellular, pleomorphic, acid-fast, pathogenic bacterium. It is an aerobic bacillus (rod-shaped bacterium) with parallel sides and round ends, surrounded by the characteristic waxy coating unique to mycobacteria. In size and shape, it closely resembles Mycobacterium tuberculosis. This bacterium often occurs in large numbers within the lesions of lepromatous leprosy that are usually grouped together like bundles of cigars or arranged in a palisade. Due t…
Microscopy
Optical microscopy shows M. leprae in clumps, rounded masses, or in groups of bacilli side by side, and ranging from 1–8 μm in length and 0.2–0.5 μm in diameter. The organism has been successfully grown on an artificial cell culture medium on a very limited basis by researcher Arvind Dhople. This can be used as a diagnostic test for the presence of bacilli in body lesions of suspected lep…
Pathogenesis
The incubation period of M. leprae can range between 9 months and 20 years. It replicates intracellularly inside histiocytes and nerve cells and has two forms. One form is "tuberculoid," which induces a cell-mediated response that limits its growth. Through this form, M. leprae multiplies at the site of entry, usually the skin, invading and colonizing Schwann cells. The microbe then induces T-helpe…
Genome
Mycobacterium leprae has the longest doubling time (at 13 days of doubling time in the mouse footpad. ) of all known bacteria and has thwarted every effort at culture in the laboratory. Comparing the genome sequence of M. leprae with that of M. tuberculosis provides clear explanations for these properties, and reveals an extreme case of reductive evolution. Less than half of the genome contains functional genes. Gene deletion and decay appear to have eliminate…
Ancient Mycobacterium leprae
Almost complete sequences of M. leprae from medieval skeletons with osteological lesions suggestive of leprosy from different Europe geographic origins were obtained using DNA capture techniques and high-throughput sequencing. Ancient sequences were compared with those of modern strains from biopsies of leprosy patients representing diverse genotypes and geographic origins, giving new insights in the understanding of its evolution and course through history, phyl…
Evolution
The closest relative to M. leprae is M. lepromatosis. These species diverged 13.9 million years ago (95% highest posterior density 8.2 million years ago – 21.4 million years ago ) The most recent common ancestor of the extant M. leprae strains was calculated to have lived 3,607 years ago [95% highest posterior density 2204–5525 years ago]. The estimated substitution rate was 7.67 x 10 …
Symptoms of Mycobacterium leprae
The symptoms of M. leprae, also known as leprosy, are unattractive skin sores that are pale in color, lumps or bumps that do not go away after several weeks or months, nerve damage which can lead to complications with the ability to sense feeling in the arms and legs as well as muscle weakness. Symptoms usually take 3–5 years from being exposed to manifest within the body. Howe…