15. RUNYON GROUPS I,II,III: Slow growing mycobacterium Visible colonies on solid media After more than 5 days incubation GROUP I: PHOTOCHROMOGENS Produce pigment When grown in the light but not the dark EXAMPLES: M. kansasii ; M. marinum ; M. simiae GROUP II: SCOTOCHROMOGENS Pigment when grown in both light and dark EXAMPLES: M. scrofulaceum ; M. szulgai ; M. xenopi GROUP III: NONCHROMOGENS No pigment when grown in both light and dark EXAMPLES: M. avium-intracellulare ; M. genevense M. ulcerans and M. leprae do not fit in this scheme
16. RUNYON GROUP IV: Rapidly growing mycobacterium Visible colonies on solid medium In less than 5 days incubation EXAMPLES: M. fortuitum ; M. chelonae ; M. abscessus
18. MYCOBACTERIUM TUBERCULOSIS Prototypic facultative intracellular pathogen Primary human pathogen Transmitted from human to human Closely related to M. bovis It is an intracellular pathogen (typically inside alveolar macrophages). This organism does not secrete an identifiable exotoxin. Host immunity to M tuberculosis appears to be cell mediated (CMI).
19. CELL ASSOCIATED TOXINS MAY BE IMPORTANT VIRULENCE FACTORS FOR MANY MYCOBACTERIA The glycolipids, such as trehalose dimycolates, of Mycobacterium tuberculosis and related organisms appear to be related to their virulence .
45. Chest Radiograph Abnormalities often seen in apical or posterior segments of upper lobe or superior segments of lower lobe May have unusual appearance in HIV-positive persons Cannot confirm diagnosis of TB Arrow points to cavity in patient's right upper lobe.
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49. Factors that affect the PPD Reaction Type of Reaction Possible Cause False-positive Nontuberculous mycobacteria BCG vaccination Anergy False-negative Recent TB infection Very young age (< 6 months old) Live-virus vaccination Overwhelming TB disease
59. DNA fingerprinting Steps: 1. Digest DNA into smaller fragments 2. Separate fragments by size 3. Visualize bands 4. Each band corresponds to 1 fragment size 5. Unique pattern of bands identifies donor of DNA
64. Tuberculosis and the Immune Reconstitution Inflammatory Syndrome (IRIS)
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71. Prevention and control of tuberculosis 1. Prompt and effective treatment of patients with active TB 2. Careful follow-up of contacts – tuberculin test, X-rays etc 3. Prophylaxis of asymptomatics, tuberculin positives 4. Correct underlying cause of immune suppression 5. Immunization with live-attenuated tubercle bacilli e.g. BCG 6. Eradication of TB in cattle and pasteurization of milk
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78. HANSEN’S DISEASE (Leprosy) caused by M. leprae Hansen’s disease is a chronic, slowly progressive Granulomatous Disease involve ectodermally derived tissues e.g. skin and peripheral nerves. Usually limited to the cooler parts of the body e.g. skin, nose and upper respiratory tract. It rarely affects internal organs such as the brain, liver, spleen, kidneys, and bones. It has a specific predilection for peripheral nerves.
79. Mycobacterium leprae is an acid-fast rod that grows in macrophages, nerve cells, the foot pads of thymectimized mice, and the nine banded armadillo. It has never been grown in artificial medium, an obligate intracellular pathogen. has a generation time of 12 to 14 days, the incubation period for onset of disease is prolonged, therapy must also be prolonged (perhaps the lifetime of the individual).
3 The global burden of tuberculosis is truly enormous with some 1.9 million deaths per year according to the most detailed country-based analysis yet carried out and reported last year by the surveillance and monitoring unit of WHO's Communicable Disease Operational and Epidemiological Research Unit. Some 380,000 of these deaths occur in HIV infected individuals largely, but not solely, in Africa. And 98% of these deaths occur in the developing world. Staggeringly, for a disease many of us believed would disappear in our lifetime, TB is estimated to be the commonest cause of death of young women worldwide. Worse still, but at the same time providing cause for hope, these deaths are preventable. However, persistent poor practice in many countries is raising the spectre of multi-drug resistant (MDR) TB. This form of TB, if it became widely established, would make the control of the disease beyond the financial capacity of many countries.
3 The global burden of tuberculosis is truly enormous with some 1.9 million deaths per year according to the most detailed country-based analysis yet carried out and reported last year by the surveillance and monitoring unit of WHO's Communicable Disease Operational and Epidemiological Research Unit. Some 380,000 of these deaths occur in HIV infected individuals largely, but not solely, in Africa. And 98% of these deaths occur in the developing world. Staggeringly, for a disease many of us believed would disappear in our lifetime, TB is estimated to be the commonest cause of death of young women worldwide. Worse still, but at the same time providing cause for hope, these deaths are preventable. However, persistent poor practice in many countries is raising the spectre of multi-drug resistant (MDR) TB. This form of TB, if it became widely established, would make the control of the disease beyond the financial capacity of many countries.
With decreasing CD4 T cells, the clinical manifestation changes from pulmonary to more severe forms of TB Like disseminated tuberculosis With increasing immunosuppression not only the risk of tuberculosis increases, but also the clinical manifestation of the disease changes as this compilation of several studies demonstrates. Early in the course of immunosuppression, pulmonary tuberculosis is the most frequent manifestation. At the other extreme with very low CD4 cell counts, disseminated forms of tuberculosis are frequent.
Period 1984 –2000 Death rate between 5% and 10% failure rate between 1% and 5% Study - HIV positive patients had higher mortality rate. 35% in HIV positive, and 13% in HIV negative patients. Mortality was strongly related to HIV infection, during treatment and three years after treatment.
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