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Mycobacterium tuberculosis

Mycobacterium tuberculosis (MTB) is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis. Robert Koch first discovered it in 1882 and that it had an unusual, waxy coating on the cell surface which makes them impossible to Gram stain. M. tuberculosis is highly aerobic and requires high levels of oxygen. It generally infects the respiratory system of mammals. Tuberculin skin test, acid-fast stain, and chest radiographs are the most frequently used diagnostic methods.

The genome was sequenced in 1998. M. tuberculosis requires oxygen to grow and due to its high lipid content in its wall it does not retain any bacteriological stain. They are classified as acid-fast Gram-positive bacteria due to their lack of an outer cell membrane.

It divides every 15-20 hours which is slow compared to other bacteria. It can withstand weak disinfectants and can survive in a dry state for weeks. Alveolar macrophages take up M. tuberculosis when in the lungs. The cell walls prevent the fusion of the phagosome with a lysosome. The bacteria multiply unchecked within the macrophage.

Through mutants and test individual gene products for specific functions has significantly advanced our understanding of the pathogenesis and virulence factors of M. tuberculosis. It comes from the genus Mycobacteriums which is composed of approximately 100 recognized and proposed species.

Mycobacterium tuberculosis and Mycobacterium leprae are the most familiar species. Phenotypic studies suggest this strain variation never has implications for the development of new diagnostics and vaccines. The relative fitness and transmission dynamics of antibiotic-resistant strains is affected by microevolutionary variations.

Outbreaks are often cause by hypervirulent strains of M. tuberculosis. These hypervirulent mutants have modified cell walls that respond to environmental stimuli. The genome contains 250 genes involved in fatty acid metabolism, with 39 of these involved in the polyketide metabolism generating the waxy coat. This large number of genes shows the evolutionary importance of the waxy coat to pathogen survival.

Only 10% of people infected ever develop the disease and most of those only have the disease only for the first few years following infections.

Symptoms are unusual and usually don’t appear until the disease has progressed to a more complicated stage. A cough is the first symptom which later progress to appetite, fever, productive cough and loss of energy or loss of weight or night sweats.

Infection can spread to other parts of the body, especially in patients with a weakened immune system. This is referred to as military tuberculosis. People who contract it experience fever, weight loss, weakness and a poor appetite.

Tuberculosis causing lung disease may result in tuberculous pleuritis, a condition that may cause symptoms such as chest pain, nonproductive cough and fever. Dormant tuberculosis may return after a certain period of time. Other symptoms may occur, depending on the exact site of the spread. Fatigue, swelling, slight tenderness and appendicitis like pain are likely to occur if the infection spreads. Painful urination might be a sign the infection has reached the bladder. It affects the bones in children and can cause mild swelling and minimal pain. It affects the pericardium.

Advance stages of tuberculosis the organism may infect almost any part of the body. Treatment is administered on an outpatient bases and consists mostly of medications. Usual treatment is given for six to nine months according to a therapy regimen consisting of two months of isoniazid, rifampin, and pyrazinamide, four months of isoniazid and rifampin, and ethambutol or streptomycin until the drug sensitivity is known.

Antibiotics are part of therapy in people who have no symptoms and whose germs are in an inactive state. Isoniazid is taken to prevent future activation. It can not be taken during pregnancy or in people who suffer from liver disease or alcoholism. Some life-threatening side effects have been reported. One of those side effects being peripheral neuropathy. Patients have active bacteria are usually treated with a combination of medications.

Treatment usually lasts for a few months but can last up to a few years in some cases. Treatment success rate is related to a patient’s compliance and ability to take the drugs as prescribed.

Mycobacterium tuberculosis


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