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MYCOBACTERIA

Explore the history of mycobacterial diseases like TB, factors contributing to its rise, persons at risk, virulence mechanisms, and laboratory diagnosis. Learn about TB progression, nucleic acid probes, and sequencing.

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MYCOBACTERIA

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  1. MYCOBACTERIA Dr.Qurat-Ul-Ain Senior Demonstrator Microbiology, KEMU, Lahore

  2. Mycobacterial Clinical Syndromes

  3. History • TB has been known as Pthisis, • King’s Evil, • Pott’sdisease, consumption, • the White Plague. • Egyptian mummies from 3500 BCE have the presence of Mycobacterium tuberculosis

  4. Factors Contributing to the Increase in TB Cases • HIV epidemic • Increased immigration from high-prevalence countries • Transmission of TB in congregate settings (e.g., correctional facilities, long term care) • Deterioration of the public health care infrastructure

  5. Persons at Risk for Developing TB Disease • Persons at high risk for developing TB disease fall into 2 categories • Those who have been recently infected • Those with clinical conditions that increase their risk of progressing from LTBI to TB disease

  6. Recent Infection as a Risk Factor Persons more likely to have been recently infected include • Close contacts to persons with infectious TB • Skin test converters (within past 2 years) • Recent immigrants from TB-endemic areas (within 5 years of arrival to the U.S.) • Children ≤ 5 years with a positive TST • Residents and employees of high-risk congregate settings (e.g. correctional facilities, homeless shelters, healthcare facilities)

  7. Increased Risk for Progression to TB Disease Persons more likely to progress from LTBI to TB disease include • HIV infected persons • Those with history of prior, untreated TB • Underweight or malnourished persons • Injection drug use • Those receiving TNF-α antagonists for treatment of rheumatoid arthritis or Crohn’s disease • Certain medical conditions

  8. Virulence Mechanisms of TB 1. TB mechanism for cell entry • The tubercle bacillus can bind directly to mannose receptors on macrophages via the cell wall-associated mannosylated glycolipid 2. TB can grow intracellularly • Effective means of evading the immune system • Once TB is phagocytosed, it can inhibit phagosome-lysosome fusion • TB can remain in the phagosome or escape from the phagosome ( Either case is a protected environment for growth in macrophages)

  9. Virulence mechanisms of TB 3. Slow generation time • Immune system cannot recognize TB, or cannot be triggered to eliminate TB 4. High lipid concentration in cell wall • accounts for impermeability and resistance to antimicrobial agents • Accounts for resistance to killing by acidic and alkaline compounds in both the inracellular and extracelluar environment • Also accounts for resistance to osmotic lysis via complement depostion and attack by lysozyme

  10. Progression of TB

  11. Progression of TB

  12. Progression of TB

  13. Nucleic acid probes Nucleic acid sequencing Laboratory Diagnosis of Mycobacterial Disease

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