infectious diseases n.
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Infectious Diseases

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  1. Infectious Diseases Dr. Meg-angela Christi Amores

  2. Infectious Diseases • Tuberculosis • Leprosy • AIDS • Syphilis • Viral Infections • Pneumonia • Herpes

  3. TUBERCULOSIS • one of the oldest diseases to affect humans • caused by bacteria of the Mycobacterium tuberculosis complex • Usually affects the lungs • untreated, the disease may be fatal within 5 years in 50–65% of cases • airborne spread of droplet nuclei

  4. M. Tuberculosis • rod-shaped, non-spore-forming, thin aerobic bacterium measuring 0.5 um by 3 um • Acid-fast (once stained, cannot be decolorized by acid alcohol)

  5. From infection to disease • the risk of developing disease after being infected depends largely on endogenous factors, such as the individual's immunity • primary tuberculosis – • Clinical illness directly following infection • common among children up to 4 years of age and among immunocompromised persons

  6. secondary (or postprimary) tuberculosis • Dormant bacilli persisting for years before reactivating • Mostly in adults • Pulmonary findings

  7. Pathogenesis and Immunity • Infection and Macrophage Invasion • Virulence of Tubercle Bacilli • Innate Resistance to Infection • The Host Response • phagosomes and lysosomes occurs • bacilli begin to multiply, ultimately killing the macrophage

  8. Pathogenesis and Immunity • Granuloma Formation • macrophages • The Macrophage-Activating Response • Caseous necrosis • The Delayed-Type Hypersensitivity Reaction • Role of Macrophages and T lymphocytes • Mycobacterial Lipids and Proteins

  9. Immunity • Skin Test Reactivity • PPD Skin test: • Due to delayed-type sensitivity • Coincident with immunity • Positive Tuberculin Skin Test (TST): wheal • > 5mm on un-vaccinated persons • >10 mm on vaccinated persons • After 72 hours

  10. Clinical Manifestations • PULMONARY • EXTRA-PULMONARY

  11. Pulmonary TB • Primary • Mostly seen in children • most inspired air is distributed to the middle and lower lung zones, these areas of the lungs are most commonly involved in primary tuberculosis • lesion heals spontaneously and may later be evident as a small calcified nodule (Ghon lesion) • immunocompromised persons develop miliary TB

  12. Pulmonary TB • Secondary (Postprimary) • adult-type, reactivation • localized to the apical and posterior segments of the upper lobes, where the substantially higher mean oxygen tension favorsmycobacterial growth • small infiltrates to extensive cavitary disease

  13. Clinical Manifestations • fever and night sweats, weight loss, anorexia, general malaise, and weakness • cough eventually develops—often initially nonproductive and subsequently accompanied by the production of purulent sputum, sometimes with blood streaking • Often with no physical findings

  14. Extrapulmonary TB • Lymph-Node Tuberculosis • frequent among HIV-infected patients • historically referred to as scrofula • Pleural TB • TB of upper airways • Genitourinary TB • TB Meningitis and Tuberculoma • Gastrointestinal TB

  15. Extrapulmonary TB • Skeletal TB • reactivation of hematogenous foci or to spread from adjacent paravertebral lymph nodes • spine in 40% of cases, the hips in 13%, and the knees in 10% • Spinal tuberculosis (Pott's disease or tuberculousspondylitis) • With advanced disease, collapse of vertebral bodies results in kyphosis (gibbus)

  16. Extrapulmonary TB • Miliary TB • Disseminated TB • yellowish granulomas 1–2 mm in diameter that resemble millet seeds • chest radiography reveals a miliaryreticulonodular pattern

  17. Diagnosis • High index of suspision • XRAY consistent with TB • AFB microscopy: • Sputum exam • Tissue biopsy • Culture • Gold standard

  18. Treatment • DOTS ( Direct Observed Treatment Strategy) • Treatment partner