3. Lower Respiratory Tract

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3. Lower Respiratory Tract
2011-08-11 03:36:46
PH162A midterm3

public health microbiology midterm 3 lecture 3
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  1. pneumonia
    • acute inflammation of alevolar tissue in the lung
    • 3rd cause of death worldwide, leading cause of death from infectious diseases
  2. pneumonia etiology
    can be caused by all groups of organisms discussed
  3. sputum
    mucus, leukocytes and inflammatory fluid that has exited the capillaries into the lungs
  4. 2 forms of pneumonia
    scant sputum, dry cough - usually intracellular organisms

    copious sputum, productive cough - extracellular growth
  5. streptococcus pneumoniae
    • gram-positive cocci in pairs
    • alpha hemolytic
    • pneumococcal pneumonia
  6. pneumococcal pneumonia occurrence
    • most common cause of community acquired pneumonia in people over 50
    • 1/4 of people hospitalized with it die
    • most common bacterial complication of influenza
  7. pneumococcal pneumonia transmission
    respiratory route through large and medium droplets
  8. pneumococcal pneumonia pathogenesis
    • capsule prevents initial phagocytosis
    • induces strong inflammatory response
    • attachment mediated through a variety of proteins (no pili)
    • can spread to other parts of boy and cause different diseases
    • host produces specific antibody that opsonizes (along with C3b) and facilitates phagocytosis
    • antibodies are not cross reactive - does not protect from infection from other types
  9. pneumococcal pneumonia clinical
    • most infections are asymptomatic or mild
    • when symptomatic, can cause variety of diseases - ear infection, pneumonia, bacteremia, meningitis
  10. clinical manifestations of pneumonia
    • rigor (shaking chill)
    • high fever
    • productive coughing (inflammatory fluid in lungs)
    • death due to drowning in inflammatory fluid
  11. pneumococcal pneumonia diagnosis
    • gram stain from sputum and sterile sites - gram+ cocci
    • culture - alpha-hemolysis, catalase negative, susceptibility to optochin, bile soluble
    • slide agglutination and coagulation
    • DNA and RNA probes
    • lab diagnosis crucial
  12. pneumococcal pneumonia treatment
    antibiotics - resistance problem
  13. pneumococcal pneumonia prevention
    23-valent polysaccharide vaccine - recommended for people who are older with underlying disease

    13-valent polysaccharide conjugate vaccine - for young children
  14. Tuberculosis (TB)
    • about 1/3 of the world's population is infected with the bacteria
    • declared global emergency, more people die of TB now than before
  15. Tuberculosis etiology
    • mycobacterium tuberculosis
    • has characteristic cell wall with a high amount of mycolic acid - acid-fast bacillus
  16. Tuberculosis occurrence
    • mostly a disease of poverty
    • 13 countries responsible for 75% of world's TB cases
    • rare in US
  17. Tuberculosis transmission
    • respiratory route
    • airborne in droplet nuclei
    • low infectious dose
    • spread by people with active disease, not subclinical carriers
  18. Tuberculosis primary disease
    • bacteria establish infection in lungs
    • phagocytosed by dendritic cells and macrophages
    • produce a granulomatous lesion called a tubercle
    • delayed type hypersensitivity reaction -T cell mediated
    • disease manifestation depends on bacterial proliferation, dissemination, and CMI response
  19. Latent Tuberculosis
    • immune response controls infection, but doesn't clear bacteria
    • person latently infected does not transmit disease
  20. Tuberculosis reactivation disease
    • proliferation of bacteria already in lungs (granuloma)
    • usually occurs when there is deterioration in host immune function
  21. Tuberculosis clinical
    • iceberg concept
    • may form granuloma and control disease that way unless bacteria escape
    • genetics, nutritional status and immune status play a role in who develops
  22. Tuberculosis clinical manifestations
    • persistent cough
    • weight loss
    • weakness
    • fever
    • drenching night sweats
    • blood coughed up from lungs
    • can spread and damage other organs
  23. Tuberculosis diagnosis challenge
    • without proper diagnosis treatment is delayed
    • time between onset of cough and healthcare provider, correct diagnosis, and treatment
  24. diagnosis of latent infection
    • tuberculin skin test:
    • indicates infection or exposure not active disease
    • material from bacterial cell wall inject intradermally
    • test measures cell mediated immune response

    • interferon-gamma release assay:
    • measures cytokine activity
    • advantages - not affected by vaccine, less subjective, patient does not have to return
    • disadvantages - needs freshly collected blood

    • chest x-ray:
    • determine if disease is active
  25. diagnosis of active disease
    staining of sputum for presence of antigen used most
  26. cepheid gene Xpert MTB/Rif
    rapid diagnostic for detection of TB and rifampicin resistance
  27. Tuberculosis treatment
    • used to be sent to sanitoriums for fresh air, rest, sun
    • drug therapy - resistance is problem
  28. Tuberculosis drug resistance
    • multidrug-resistant TB
    • extensively drug-resistant TB
    • drug resistance caused exclusively by mutation targets, no horizontal gene transfer
  29. Tuberculosis prevention
    • treatment of latent carriers - secondary prevention, prevents forming active disease
    • isoniazid prophylaxis of contacts used in US as well
    • treatment of people with active disease to prevent spread
    • vaccine - not used in US because of skin test
    • directly observed treatment short-course
  30. respiratory mycoses
    infection of the respiratory tract with fungi
  31. respiratory mycoses etiology and diseases they cause
    • histoplasma capsulatum - histoplasmosis
    • coccidiodes immitis - coccidioidomycosis (valley fever)
    • blastomyces dermatitidis - blastomycoses
  32. respiratory mycoses reservoir
    • soil
    • histoplasma capsulatum - midwestern US
    • coccidiodes immitis - central valley, southwestern, northwestern mexico
    • blastomyces dermatitidis - southeastern US
  33. respiratory mycoses transmission
    • by inhalation of conidia from soil
    • not communicable
  34. respiratory mycoses pathogenesis
    • inhaled conidia germinate into yeast form in the host's lungs
    • innate and CMI cause grauloma formation like TB
  35. respiratory mycoses clinical
    • most people have mild or no symptoms
    • small percentage of people develop severe disease, similar to TB
  36. respiratory mycoses diagnosis
    • skin test for H. capsulatum and C. immitis
    • culture gives definitive diagnosis
    • x-ray to show extent of disease
    • medical history including geographic location
  37. respiratory mycoses treatment
    antifungals - severe side effects
  38. respiratory mycoses prevention
    • no successful vaccines
    • modification of soil - dust control measure, cleaning up bird droppings