Question

What is Mycobacterum tuberculosis, and what is the morphology, gram stain characteristics, virulence factors, susceptibility to antibiotics, host cells, nutritional needs, growth conditions, mechanisms used to evade the immune system and invasion into the host(s), interactions with the hosts and diseases caused and affected body systems. Additionally, students should explain symptoms when the Mycobacterum tuberculosis infects a host, as well as a diagnosis and the therapeutic intervention needed after infection. You may also add information on statistics related to infection (epidemiology) and any new research findings related to the pathogen.

Answer 1

Mycobacterium tuberculosis is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis.Mycobacterium tuberculosis (MTB) is an ancient infectious disease that has appeared once again as a serious worldwide health problem and now comprises the second leading cause of deaths resulting from a single infection. . It is an airborne, infectious disease caused by bacteria which primarily affects the lungs.

Morphology of mycobacterium tuberculosis

Straight or slightly curvedrod, about 3 x 0.3 micrometers

Occuring singly, in pairs or as small clumps.

Long filamentous,club- shaped and branching forms may sometimes be seen.

Gram stain characteristics

Tubercle bacilli have been described as Gram positive, though strictly speaking this is not correct, as after staining with basic dyes they resist decolourization by alcohol even without the mordanting effect of iodine.They cannot be stained by the Gram stain because of their high lipid content. Acid fast staining is used to stain mycobacteria. Bacteria are treated with a red dye (fuchsin) and steamed. (This drives the stain into the cell and because of the lipid, they become difficult to destain).

virulence factors of mycobacterium tuberculosis

Phthiocerol dimycocerosate (PDIM) and phenolic glycolipids (PGL) Phthiocerol dimycocerosate (PDIM) and phenolic glycolipids (PGL) include a group of related cell wall lipids, non-covalently bounded to the mycobacterial surface. PDIM and PLG are major virulence factors of mycobacteria.

Susceptibility to antibiotic

Drug susceptibility of M. tuberculosis can be determined either by observation of growth or metabolic inhibition in a medium containing antituberculosis drug, or by detection, at the molecular level, of mutations in the genes related to drug action.

Antimicrobial susceptibility testing of Mycobacterium tuberculosis complex for first and second line drugs by broth dilution in a microtiter plate format. ... If there is ≥1% growth on the drug-containing medium as compared to drug-free medium, the organism is considered resistant to that drug.

Antituberculous drugs are of two types,

Bactericidal : Rifampicin, Pyrazinamide, are called sterilizing drugs because they are able to effectively kill the bacilli in the lesions.

Bacteristatic

The bactericidal drugs, along with the bacteristatic drug ethambutol ,constitute the first line drugs in antituberculous therapy.

Host cells

Once in the lower respiratory tract, Mycobacterium tuberculosis  is primarily phagocytosed by macrophages and dendritic cells. In addition to macrophages and dendritic cells, studies analysing the sputum of TB patients identified neutrophils as the predominant phagocytic cell infected with mycobacterium tuberculosis.

Nutritional need

The risk of complications including death from infections is influenced by the nutritional status of an individual, but the nutritional status of an individual and utilization of nutrients are also adversely affected following an infection.

• Energy needs of TB patients are increased because of the disease itself. The current recommendations for TB patients are based on the nutrient and energy requirements for hyper catabolic and undernourished patients.

• The protein intake of the diet is important to prevent the wasting of body stores (for example muscle tissues).

• Micronutrients: about the exact vitamin and trace element requirements in infection and the effects of micronutrient supplementation on TB treatment outcomes, clinical complications, and mortality are uncertain.A good multivitamin and mineral supplement, therefore providing 50% -150% of the recommended daily allowance.

Drug -nutrient interactions Isoniazid is one of the most frequently anti-tuberculosis drugs used in the treatment of the disease. The drug is an antagonist of vitamin B6 (pyridoxine) and may case peripheral neuropathy (relatively rare) due to a nutritional deficiency of vitamin B6. It is standard procedure to supplement adults with 25 mg of vitamin B6 per day (in the form of supplements).

Growth conditions

Mycobacterium tuberculosis grows slowly: it reproduces itself every 24 to 48 hours. This is extremely slow for bacteria. There are other bacteria that reproduce every 20 minutes. ... Usually bacteria are identified by adding coloring agents to the laboratory surface on which they grow.Tuberculosis must acquire sufficient Mg2+ in order to grow in a mildly acidic environment such as within the phagosome of macrophages. M. tuberculosis grows within the phagocytic vacuoles of macrophages.

Mechanisms used to evade the immune system and invasion into the host(s)

M. tuberculosis infects a person, it attacks the lungs' first-response immune cells, the macrophages. The immune response by the macrophages involves a complex of four different proteins called the "inflammasome." The main role of the inflammasome is to prepare certain immunity proteins in the macrophages, which are called "interleukins." When M. tuberculosis infects the lungs, interleukins from the macrophages are in the first line of defense.

If it is left uncontrolled, this defense can also cause serious damage to the patient. To prevent this, macrophages also release another group of proteins called "type I interferons." While interferons are important for defending the body against viruses, when it comes to tuberculosis they actually help the bacterium, thereby exacerbating the disease. And although the interleukin-inflammation part of the immune response is rather well understood, the part involving interferons has been elusive.

Interactions with the hosts and diseases caused and affected body systems

A person gets active TB disease, it means TB bacteria are multiplying and attacking the lung(s) or other parts of the body, such as the lymph nodes, bones, kidney, brain, spine, and even the skin. From the lungs, TB bacteria move through the blood or lymphatic system to different parts of the body.

symptoms

TB bacteria most commonly grow in the lungs, and can cause symptoms such as: A bad cough that lasts 3 weeks or longer. Pain in the chest. Coughing up blood or sputum (mucus from deep inside the lungs)

Diagnosis and the therapeutic intervention

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.

The most common medications used to treat tuberculosis include:

• Isoniazid.
• Rifampin (Rifadin, Rimactane)
• Ethambutol (Myambutol)
• Pyrazinamide.