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Chapter 24

Chapter 24. Microbial Diseases of the Respiratory System. Microbial Diseases of the Upper Respiratory System. Laryngitis: S. pneumoniae , S. pyogenes , viruses Tonsillitis: S. pneumoniae , S. pyogenes , viruses Sinusitis: Bacteria Epiglottitis: H. influenzae. Upper Respiratory System.

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Chapter 24

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  1. Chapter 24 Microbial Diseases of the Respiratory System

  2. Microbial Diseases of the Upper Respiratory System • Laryngitis: S. pneumoniae, S. pyogenes, viruses • Tonsillitis: S. pneumoniae, S. pyogenes, viruses • Sinusitis: Bacteria • Epiglottitis: H. influenzae

  3. Upper Respiratory System • Upper respiratory normal microbiota may include pathogens Figure 24.1

  4. Streptococcal pharyngitis (Strep throat) • Streptococcus pyogenes • Resistant to phagocytosis • Streptokinases lyse clots • Streptolysins are cytotoxic • Diagnosis by indirect agglutination Figure 24.3

  5. Scarlet Fever • Streptococcus pyogenes • Pharyngitis • Erythrogenic toxin produced by lysogenized S. pyogenes Figure 24.4

  6. Diphtheria • Corynebacterium diphtheriae: Gram-positive rod • Diphtheria membrane of fibrin, dead tissue, and bacteria • Diphtheria toxin produced by lysogenized C. diphtheriae • Prevented by DTaP and Td vaccine (Diphtheria toxoid) • Cutaneous diphtheria: Infected skin wound leads to slow healing ulcer

  7. Diphtheria Figure 24.6

  8. Otitis Media • S. pneumoniae (35%) • H. influenzae (20-30%) • M. catarrhalis (10-15%) • S. pyogenes (8-10%) • S. aureus (1-2%) • Treated with broad-spectrum antibiotics • Incidence of S. pneumoniae reduced by vaccine

  9. Otitis Media Figure 25.7

  10. Common cold • Rhinoviruses (50%) • Coronaviruses (15-20%) • Rhinoviruses attached to ICAN-1 on nasal mucosa

  11. Microbial Diseases of the Lower Respiratory System • Bacteria, viruses, & fungi cause: • Bronchitis • Bronchiolitis • Pneumonia

  12. Lower Respiratory System • The ciliary escalator keeps the lower respiratory system sterile. Figure 24.2

  13. Pertussis (Whooping Cough) • Bordetella pertussis: Gram-negative coccobacillus • Capsule • Tracheal cytotoxin of cell wall damaged ciliated cells • Pertussis toxin • Prevented by DTaP vaccine (acellular Pertussis cell fragments) Figure 24.8

  14. Pertussis (Whooping Cough) • Stage 1: Catarrhal stage, like common cold • Stage 2: Paroxysmal stage: Violent coughing sieges • Stage 3: Convalescence stage

  15. Tuberculosis • Mycobacterium tuberculosis: Acid-fast rod. Transmitted from human to human • M. bovis: <1% U.S. cases, not transmitted from human to human • M. avium-intracellulare complex infects people with late stage HIV infection Figure 24.9

  16. Tuberculosis Figure 24.10.1

  17. Tuberculosis Figure 24.10.2

  18. Tuberculosis Figure 24.10.3

  19. Tuberculosis • Treatment of Tuberculosis: Prolonged treatment with multiple antibiotics • Vaccines: BCG, live, avirulent M. bovis. Not widely used in U.S.

  20. Tuberculosis • Diagnosis: Tuberculin skin test screening • + = current or previous infection • Followed by X-ray or CT, acid-fast staining of sputum, culturing bacteria Figure 24.11

  21. Tuberculosis Figure 14.11c

  22. Tuberculosis Figure 24.12

  23. Pneumomoccal Pneumonia • Streptococcus pneumoniae: Gram-positive encapsulated diplococci • Diagnosis by culturing bacteria • Penicillin is drug of choice Figure 24.13

  24. Pneumomoccal Pneumonia

  25. Haemophilus influenzae Pneumonia • Gram-negative coccobacillus • Alcoholism, poor nutrition, cancer, or diabetes are predisposing factors • Second-generation cephalosporins

  26. Mycoplasmal Pneumonia • Mycoplasma pneumoniae: pleomorphic, wall-less bacteria • Also called primary atypical pneumonia and walking pneumonia • Common in children and young adults • Diagnosis by PCR or by IgM antibodies Figure 24.14

  27. Mycoplasmal Pneumonia Figure 11.19a, b

  28. Legionellosis • Legionella pneumophila: Gram-negative rod • L. pneumophila is found in water • Transmitted by inhaling aerosols, not transmitted from human to human • Diagnosis: culturing bacteria • Treatment: Erythromycin

  29. Psittacosis (Ornithosis) • Chlamydia psittaci: gram-negative intracellular bacterium • Transmitted by elementary bodies from bird dropping to humans • Reorganizes into reticulate body after being phagocytized • Diagnosis: culturing bacteria in eggs or cell culture • Treatment: Tetracycline

  30. Chlamydial Pneumonia • Chlamydia pneumoniae • Transmitted from human to human • Diagnosis by FA test • Treatment: Tetracycline

  31. Q fever • Mycoplasma pneumoniae: pleomorphic, wall-less bacteria • Also called primary atypical pneumonia and walking pneumonia • Common in children and young adults • Diagnosis by PCR or by IgM antibodies

  32. Q fever Figure 24.15

  33. Viral Pneumonia • Viral pneumonia as a complication of influenza, measles, chickenpox • Viral etiology suspected if no cause determined • Respiratory Syncytial Virus (RSV) • Common in infants; 4500 deaths annually • Causes cell fusion (syncytium) in cell culture • Symptoms: coughing • Diagnosis by serologic test for viruses and antibodies • Treatment: Ribavirin

  34. Influenza • Chills, fever, headache, muscle aches (no intestinal symptoms) • 1% mortality due to secondary bacterial infections • Treatment: Amantadine • Vaccine for high-risk individuals

  35. Influenza • Hemagglutinin (H) spikes used for attachment to host cells • Neuraminidase (N) spikes used to release virus from cell

  36. Influenza Figure 24.16

  37. Influenza • Antigenic shift • Changes in H and N spikes • Probably due to genetic recombination between different strains infecting the same cell • Antigenic drift • Mutations in genes encoding H or N spikes • May involve only 1 amino acid • Allows virus to avoid mucosal IgA antibodies

  38. Influenza serotypes • A: causes most epidemics, H3N2, H1N1, H2N2 • B: moderate, local outbreaks • C: mild disease

  39. Histoplasmosis • Histoplasma capsulatum, dimorphic fungus (a) 37˚ (a) >35˚ Figure 24.17

  40. Histoplasmosis • Transmitted by airborne conidia from soil • Diagnosis by culturing fungus • Treatment: amphotericin B Figure 24.18

  41. Coccidioidomycosis • Coccidioides immitis Figure 24.19

  42. Coccidioidomycosis • Transmitted by airborne arthrospores • Diagnosis by serological tests or DNA probe • Treatment: amphotericin B Figure 24.20

  43. Pneumocystis Pneumonia • Pneumocystis jiroveci (P. carinii) found in healthy human lungs • Pneumonia occurs in newly infected infants & immunosuppressed individuals • Treatment: Timethoprim-sulfamethoxazole Figure 24.22

  44. Pneumocystis 1 The mature cyst contains 8 intracystic bodies. Cyst 2 The cyst ruptures, releasing the bodies. Intracystic bodies 5 Each trophozoite develops into a mature cyst. 3 The bodies develop into trophozoites. 4 The trophozoites divide. Trophozoite Figure 24.21

  45. Blastomycosis • Blastomyces dermatitidis, dimorphic fungus • Found in soil • Can cause extensive tissue destruction • Treatment: amphotericin B

  46. Opportunistic fungi involved in respiratory disease: • Aspergillus • Rhizopus • Mucor Mucor rouxii Figure 12.2b, 12.4

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