Group 1 Mycobacteria PDF

MYCOBACTERIUM GRAM- POSI TI VE SLENDER NON-MOTI LE NON-SPOR E FORMI NG ROD-SHAPED BACI LLI PLEOMOR PHI C AEROBI C HYDROPHOBI C ID 01. P H E N O T Y P I C & B I O CHEM I C A L C HA R A C TER I S TI C S 02. ADDITIONAL TECHNIQUES 03. A D V A N C E S I N M O L ECUL A R M ETHO DS 04. Z I E H L...

MYCOBACTERIUM GRAM- POSI TI VE SLENDER NON-MOTI LE NON-SPOR E FORMI NG ROD-SHAPED BACI LLI PLEOMOR PHI C AEROBI C HYDROPHOBI C ID 01. P H E N O T Y P I C & B I O CHEM I C A L C HA R A C TER I S TI C S 02. ADDITIONAL TECHNIQUES 03. A D V A N C E S I N M O L ECUL A R M ETHO DS 04. Z I E H L - N E E L S EN S T A I NI NG ANTIGENIC STRUCTURE C E L L W A L L A NT I G ENS PEPTIDOGLYCAN - maintains shape rigidity ARABINOGALACTAN - survival within macrophages MYCOLIC ACID - intracellular survival, resistance to heat and chemical disinfectants SULFOLIPIDS - prevent phagosome-lysosome fusion C Y T O P L A S M I C A NT I G ENS PROTEINS - interfere with host cell signaling antigen 5 antigen 6 antigen 60 REGULATION OF VIRULENCE DETERMINANTS Mycobacterium tuberculosis Immune modulation Ability to interfere with host cell signalling pathways allows it to carefully balance production of cytokines involved in activation of the pro-inflammatory and anti-inflammatory response. By balancing the pro- and anti-inflammatory immune response, Mtb delays phagosome maturation, harvests essential nutrients and stimulates the formation of granulomas. At early infection states, these granulomas are initially dominated by alveolar macrophages and shield the bacteria from more effective immune cells. Dormancy Enters a metabolically near inactive and non-replicating dormant state in which it is immune to most types of drugs. Mtb manipulates the macrophages to accumulate lipids, providing it with nutrients required to sustain dormancy for multiple decades. Phagosomal rupture Mtb has a highly regulated pore formation system that it uses to rupture phagosome and gain cytosolic access, resulting into necrosis of the host cell and dissemination of the bacilli. REGULATION OF VIRULENCE DETERMINANTS Mycobacterium leprae Iron utilization Helps the pathogen acquire growth (NRAMP proteins allow transportation of iron into the macrophage for survival.) Macrophage invasion Replicates and survives in macrophages, dividing to approx. 100 organisms per cell. The bacteria prevent phagosome and lysosome fusion to avoid degradation. Waxy exterior Allows for intake into the macrophage and into some dendritic cells, in which it can survive. Schwann cell invasion Major target of Mycobacterium leprae. Drug resistance 182 resistance traits (Cambau et al., 2018). PATHOLOGY The creation and development of lesions and their healing and progression are determined mostly by (1) the number of mycobacteria and their multiplication and (2) the type of host and their immune response. Mycobacterium tuberculosis A. 2 Principal Lesions Exudative type consists of acute inflammatory reaction with edema fluid; polymorphonuclear leukocytes; and, later monocytes around the tubercle bacilli. Commonly seen in lung tissue. Productive (proliferative) type Consist of three zones: (1) a central area of large multinucleated cells containing tubercle bacilli; (2) a mid zone of pale epithelioid cells; (3) a peripheral zone of fibroblasts, lymphocytes, and monocytes. PATHOLOGY Mycobacterium tuberculosis B. Spread of Organisms in the Host it spreads in the host by direct extension via the lymphatic channels and blood stream, and via the bronchi and gastrointestinal tract. In the first infection: tubercle bacilli spread from the initial site via lymphatics to the regional lymph nodes and may spread father and reach the bloodstream which consequently distributes it to all organs. C. Intracellular Site of Growth When mycobacteria establishes themselves in the tissue, they reside principally in monocytes, reticuloendothelial cells, and giant cells. PATHOLOGY Mycobacterium leprae Preferentially invades dermal histocytes (tissue macrophages) and Schwann cells in peripheral nerves which leads to injury of the nerve, demyelination, and consequent disability. It primarily invade the schwann cells by binding to the alphadystroglycan (DG) via the interaction of alpha-DG and laminin (LN)-alpha2 in the basal lamina that surrounds the Schwann cell-axon unit. The infection remains localized to the PNS by rolling and binding to exposed schwann cells. ENZYMES Catalase protects bacteria against lethal hydrogen peroxide by breaking it down into water and oxygen. Types: heat-stable M-catalase - produced in response to nutrient depletion heat-labile T-catalase - produced in response to oxidative stress Urease Hydrolyzes urea to form ammonia and carbon dioxide A virulence factor in pathogenic mycobacteria as it is essential in colonizing the host and maintaining bacterial cells in tissues. Arylsuphatase Catalyzes the hydrolysis of aromatic sulfate esters and is involved in organosulfur compound metabolism where sulfur is obtained. Bacteria need arylsulphatase for sulfur, making it crucial to biosynthesis in many microorganisms. Pyrazinamidase Important enzyme that hydrolyzes pyrazinamide to pyrazinoic acid, which inhibits mycolic acid synthesis and disrupts cell wall function. Reduced pyrazinamidase activity increases resistance to pyrazinamide. TOXINS T U B E R C U L O S I S NEC R O T IZIN G TO X IN Toxin secreted by M. tuberculosis into the cytosol of infected macrophages, causing host cell death by necrosis. M Y C O L A C T O NE a diffusible lipid exotoxin produced by M. ulcerans, which causes Buruli ulcer disease. Effects: passively permeates into host cells, interacts with at least two molecular targets, and inhibits protein uptake into the endoplasmic reticulum Pathogenesis Entry into the body Multiplication and Spread Mycobacteria are released into the air as droplets less than 25 μm in diameter when infected people cough, sneeze, or talk and can linger in the air for hours. The host's immune system responds by releasing cytokines and lymphokines, which stimulate monocytes and macrophages, into the alveoli. The droplets evaporate, allowing the microorganisms to enter the lungs and reach the alveoli when inhaled. The macrophage-mediated innate immune response can generally result in three different ways: 1. Cell necrosis 2. Apoptosis 3. Survival of infected macrophages A few of the mycobacteria enter the bloodstream after which they spread all over the body. Immune Response Dendritic cells that have taken in a Mycobacteria mature, move to nearby lymph nodes, and prepare T cells to respond to mycobacterial antigens. The accumulation of various host cells results in the formation of granuloma lesions at the site of infection. When the immune system fails to control Mycobacteria, it can lead to uncontrolled multiplication of the bacteria and subsequent onset of disease. Epidemiology TUBERCULOSIS Has infected nearly 2 billion people Cases of tuberculosis are shown to be disproportionate in certain ethnic and racial minorities Untreated and chronic cases have declined alongside the duration of illness Epidemiology LEPROSY Commonly seen in tropical countries, primarily in Asia and Africa Underdeveloped countries mainly in North and South America, Africa, Southeast Asia, Western Mediterranean coast and the eastern seaboard of the Pacific Ocean are at greater risk The principal source of leprosy is untreated lepromatous patients When the right conditions are met, the microorganisms thrives in fomites and sources outside the host Clinical Findings Tuberculosis Signs and Symptoms persistent cough (>14 days) fever production of purulent and/or blood-stained sputum reduced appetite, unintentional weight loss night sweats malaise shortness of breath/difficulty in breathing Chest/back pains not referable to any musculoskeletal disorders Diagnostic Laboratory Tests 1. Direct Sputum Smear Microscopy primary diagnostic method adopted by the NTP because it provides a definitive diagnosis of TB 2. Chest X-ray complement bacteriologic testing in making a diagnosis. However, it has low specificity and does not differentiate drug-susceptible from drug-resistant disease. 3. Rapid Molecular Test Xpert MTB/RIF assay is a rapid test that detects Mycobacterium tuberculosis and rifampicin resistance. Treatment ANTIOBITIC TREATMENT DOT - directly observed treatment 1. Fixed–dose combination (FDCs) Two or more first-line anti-TB drugs are combined on one tablet. HR: isoniazid + rifampicin HRE: isoniazid + rifampicin + pyrazinamide HRZE: isoniazid + rifampicin + pyrazinamide + ethambutol 2. Single drug formulation (SDF) Each drug is prepared individually, either as tablet, capsule, syrup or injectable (Streptomycin) form. Clinical Findings Leprosy or Hansen’s Disease Signs and Symptoms discolored patches (looks pale or reddish) with loss of sensation/numbness around the area presence of nodules painless lumps on the face or earlobes skin is thick, stiff, or dry painless wounds or sores in the soles of feet painless lumps on the face or earlobes Loss of facial hair (eyebrows, eyelashes) weakness of the muscles (usually the hands and feet) enlarged nerves in the elbow, knee, or sides of the neck eye problems (can lead to blindness) Diagnostic Laboratory Tests 1. Skin and Nerve Biopsy definitively confirm a diagnosis of Hansen’s disease Skin biopsy - edges of active patches Nerve biopsy - thickened nerves 2. Slit-skin smear staining smears of dermal scrapings found in the earlobes, elbows, and knees as well as skin lesions to detect M. leprae Treatment ANTIOBITIC TREATMENT one to two years of treatment combination of antibiotics depending on the form of the disease: Paucibacillary form – 2 antibiotics: dapsone (daily) and rifampicin (once per month) Multibacillary form – clofazimine (daily) is added to rifampicin and dapsone. Drug Resistance TUBERCULOSIS Drug resistance may either be caused by extrinsic or intrinsic factors. LEPROSY Drug resistance mainly occurs due to mutations in the genes encoding drug targets changes in the cell wall’s permeability and regulation of pump proteins REFERENCES Ahmad, S. (2011). Pathogenesis, Immunology, and Diagnosis of Latent Mycobacterium tuberculosis Infection. Clinical & Developmental Immunology, 2011, 1– 17. https://doi.org/10.1155/2011/814943 Cambau, E., Saunderson, P., Matsuoka, M., Cole, S. T., Kai, M., Suffys, P., Rosa, P. 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