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Mycobacterium
- 2. Morphology • Mycobacteria are Gram-positive, catalase positive, non- motile, non-spore forming bacteria . • they are slender rod bacteria that are stained with special differential stains Ziehl-Neelsen. • They are acid fast ,as once they taken up the stain,they cant be destained with dilute acids
- 3. Medically important mycobacterium • Mycobacterium tuberculosis • Mycobacterium laprae • Nontuberculous Mycobacteria
- 4. Tuberculosis Bacteria (TB) • Tuberculosis bacteria includes the species Mycobacterium tuberculosis, M. bovis, and the rare species M. africanum. • TB are slender, acid-fast rods, 0.4 µm wide, and 3–4 µm long, nonsporing and nonmotile. • TB are obligate anaerobes. Their reproduction is enhanced by the presence of 5–10% CO2 • The generation time of TB is approximately 12–18 hours. • Grown on culture mediums with high lipid content, e.g., egg-enriched glycerol mediums according to Lo ¨wenstein-Jensen
- 5. TUBERULOSIS ( transmission) • M. tuberculosis is carried in airborne particles, called droplet nuclei, of 1– 5 microns in diameter. Infectious droplet nuclei are generated when persons who have pulmonary or laryngeal TB disease cough, sneeze, shout, or sing
- 7. • Persons with LTBI have M. tuberculosis in their bodies, but do not have TB disease and cannot spread the infection to other people. • the tubercle bacilli overcome the immune system and multiply, resulting in progression from LTBI to TB disease . • The progression from LTBI to TB disease may occur at any time, from soon to many years later. • Only 10% of LTBI reactivates into TB disease • TB disease can occur in pulmonary and extrapulmonary sites
- 8. LATENT TUBERCUL0SIS INFECTION TUBERCULOSIS INFECTION Small amount of bacteria in body ,alive but inactive Ample and Active TB in body Cant spread TB to others Infectious ,sread of TB TB skin test /TB blood test reaction shows infection TB blood and skin test rection shows infection Radiograph is normal Radiograph is abnormal Sputum smears and cultures are negative Sputum smears and cultures may be negative Not require respiratory isolation Require respiratory isolation Not a TB case A TB case
- 9. Immunity to tuberculosis • The first cells encountered by the mycobacteria in the lung are the alveolar macrophages, which respond in a non-specific manner and provide an initial line of defence. • Acquired immunity is characterized by localization of the TB at an old or new infection focus with limited dissemination (Koch’s phenomenon). This immunity is solely a function of the T lymphocytes.
- 10. Diagnoses . • The tuberculin proteins are isolated as purified tuberculin (PPD = purified protein derivative) . Five tuberculin units (TU) are applied intracutaneously in the tuberculin test (Mantoux tuberculin skin test,the“goldstandard”). • Diagnosis requires microscopic and cultural Identification of the pathogen or pathogen-specific DNA.
- 11. Epidemiology and prevention. • World wide • Less frequent in developed countries • Incidence is 5 -15 patients per 100000 inhabitants per year • Mortality is 1 per 100000 patients per year • Main Source of infection is the human carrier. • Transmission of the disease is generally direct, in most cases by droplet infection. • Patients with open tuberculosis must be isolated during the secretory phase. Secretions containing TB must be disinfected. • Tuberculous cattle must be eliminated
- 13. Etiology • Mycobacterium leprae is the causative pathogen of leprosy. In morphological terms, these acid-fast rods are identical to tuberculosis bacteria. They differ, however, in that they cannot be grown on nutrient mediums or in cell cultures •Pathogenesis. The patho mechanisms of LB are identical to those of TB. The host organism attempts to localize and isolate infection foci by forming granulomas. Leprous granulomas are histopathologically identical to tuberculous granulomas.
- 14. pathogenesis • Leprosy is manifested mainly on the skin, mucosa, and peripheral nerves. Tuberculoid leprosy Lepromatous leprosy benign malignant Non progresive form of disease progressive Characterized by spotty dermal lesions Nodular dermal and mucosal lesions develop
- 15. Epidemiology and prevention. • Rare in socially developed countries. • Infected humans are the only sourse. • Transmission pathway is unknown may be due to direct contact with skin or mucosa injuries and aerogenic transmission • . The incubation period is 2–5–20 years Diagnosis. Detection of the pathogens in skin or nasal mucosa scrapings under the microscope using Ziehl- Neelsen staining. Molecular confirmation of DNA sequences specific to leprosy bacteria in a polymerase chain reaction is possible.