Ch 24: Microbial Diseases of the Respiratory System

1. Ch 24: Microbial Diseases of the Respiratory System

2. The Upper Respiratory System Consists of: Nose Pharynx (throat) Middle ear Eustachian tubes

3. Structures of Upper Respiratory System

4. The Lower Respiratory System Consists of: Larynx Trachea Bronchial tubes Alveoli Pleura

5. Structures of Lower Respiratory System

6. The Lower Respiratory System The ciliary escalator of the lower respiratory system helps prevent microorganisms from reaching the lungs. The normal microbiota of the nasal cavity and throat can include pathogenic microorganisms. Microbes in the lungs can be phagocytized by alveolar macrophages. Respiratory mucus contains IgA antibodies.

7. Mucocilary Escalator The lower respiratory system is usually sterile because of the action of the ciliary escalator. Microorganisms hoping to infect the respiratory tract are caught in the sticky mucus and moved up by the mucociliary escalator.

8. Upper Respiratory System Diseases Most respiratory tract infections are self-limiting. Often caused by bacteria & viruses in combination

9. Upper Respiratory System Diseases Pharyngitis: inflammation of the pharynx Laryngitis: swelling and irritation (inflammation) of the voice box (larynx) Tonsillitis: inflammation of the tonsils Sinusitis: inflammation of the sinuses Epiglottitis: inflammation of the cartilage that covers the trachea H. influenzae type b *most threatening

10. Streptococcal Pharyngitis Also called strep throat Streptococcus pyogenes Gram positive cocci chains Resistant to phagocytosis Streptokinases lyse clots Streptolysins are cytotoxic Diagnosis by enzyme immunoassay (EIA) tests (have replaced latex agglutination tests)

11. Scarlet Fever Streptococcus pyogenes Pharyngitis Erythrogenic toxin produced by lysogenized S. pyogenes Symptoms include a red rash (sandpaper), high fever, and a red, enlarged tongue.

12. Diphtheria Corynebacterium diphtheriae: Gram-positive rods Diphtheria toxin produced by lysogenized C. diphtheriae

13. Diphtheria Diphtheria membrane: Fibrin, tissue, bacterial cells

14. Diphtheria Still common in developing countries where immunizations aren't given routinely. Up to 40% to 50% of those who don't get treated can die. The exotoxin inhibits protein synthesis, and heart, kidney, or nerve damage may result. Prevented by DTaP vaccine Diphtheria toxoid Cutaneous diphtheria (esp. in persons >30 yrs) Infected skin wound leads to slow-healing ulcer

15. Otitis Media Earache-can occur as a complication of nose and throat infections. Strep. pneumoniae (35%) Hem. influenzae (20–30%) Moraxella catarrhalis (10–15%) Strep. pyogenes (8–10%) Staph. aureus (1–2%) Incidence of S. pneumoniae reduced by vaccine

16. The Common Cold Any one of approximately 200 different viruses can cause the common cold; Rhinoviruses cause about 50% of all colds. Coronaviruses (15–20%) Symptoms include sneezing, nasal secretions, and congestion.

17. Rhinovirus Grow best slightly below body temperature. The incidence of colds increases during cold weather, possibly because of increased interpersonal indoor contact or physiological changes. Antibodies are produced against the specific viruses.

18. Diseases in Focus: Diseases of the Upper Respiratory System A patient presents with fever and a red, sore throat. Later, a grayish membrane appears in the throat. Gram-positive rods were cultured from the membrane. Can you identify infections that could cause these symptoms?

19. Bacteria, viruses, and fungi cause Bronchitis Bronchiolitis Pneumonia Lower Respiratory System Diseases

20. 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)

21. Pertussis (Whooping Cough) Aerosal Transmission from human to human Stage 1: Catarrhal stage, like common cold Stage 2: Paroxysmal stage—violent coughing sieges Stage 3: Convalescence stage

22. Tuberculosis Mycobacterium tuberculosis Acid-fast rod; transmitted from human to human via the gastrointestinal route

23. Tuberculosis M. bovis: <1% U.S. cases; not transmitted from human to human & usually affect the bones or lymphatic system. M. avium-intracellulare complex infects people with late-stage HIV infection The mycolic acids of the cell wall are an important factor in the pathogenicity Also gives it resistance to drying and disinfectants Lesions formed by M. tuberculosis are called tubercles; dead macrophages and bacteria form the caseous lesion that might calcify and appear in an X-ray image as a Ghon’s complex.

24. Ghon’s complex

25. Tuberculosis

26. Tuberculosis

27. Worldwide Distribution of Tuberculosis

28. U.S. Distribution of Tuberculosis

29. The Pathogenesis of Tuberculosis

30. The Pathogenesis of Tuberculosis

31. The Pathogenesis of Tuberculosis

32. The Pathogenesis of Tuberculosis

33. The Pathogenesis of Tuberculosis

34. Treatment of Tuberculosis Treatment: Prolonged treatment with multiple antibiotics Vaccines: BCG, live, avirulent M. bovis; not widely used in United States

35. A Positive Tuberculin Skin Test

36. Diagnosis of Tuberculosis Tuberculin skin test screening Positive reaction means current or previous infection Followed by X-ray or CT exam, acid-fast staining of sputum, culturing of bacteria

37. Pneumococcal Pneumonia Streptococcus pneumoniae Gram-positive encapsulated diplococci (lancet)

38. Pneumococcal Pneumonia Symptoms: Infected alveoli of lung fill with fluids; interferes with oxygen uptake Diagnosis: Optochin-inhibition test or bile solubility test; serological typing of bacteria Treatment: Penicillin, fluoroquinolones Prevention: Pneumococcal vaccine

39. Haemophilus influenzae Pneumonia Gram-negative coccobacillus Predisposing factors: Alcoholism, poor nutrition, cancer, or diabetes Symptoms: Resemble those of pneumococcal pneumonia Diagnosis: Isolation; special media for nutritional requirements (chocolate agar) Treatment: Cephalosporins

40. Mycoplasmal Pneumonia Primary atypical pneumonia; walking pneumonia Mycoplasma pneumoniae Pleomorphic, wall-less bacteria Common in children and young adults

41. Mycoplasma pneumoniae

42. Mycoplasmal Pneumonia Symptoms: Mild but persistent respiratory symptoms; low fever, cough, headache Diagnosis: PCR and serological testing Treatment: Tetracyclines

43. Legionellosis Legionella pneumophila: Gram-negative rod Legionnaires' disease acquired its name in July 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion in Philadelphia. Found in water (it’s reservoir) Transmitted by inhaling aerosols; not transmitted from human to human

44. Symptoms: Potentially fatal pneumonia that tends to affect older men who drink or smoke heavily Diagnosis: Culture on selective media, DNA probe Treatment: Erythromycin Legionellosis

45. Psittacosis (Ornithosis) Chlamydophila psittaci Gram-negative intracellular bacterium Transmitted to humans by elementary bodies from bird droppings Seldom transmitted from human to human Reorganizes into reticulate body after being phagocytized

46. Psittacosis (Ornithosis) Symptoms: Symptoms, if any, are fever, headache, chills Diagnosis: Growth of bacteria in eggs or cell culture Treatment: Tetracyclines

47. Psittacosis (Ornithosis)

48. Chlamydial Pneumonia Chlamydophila pneumoniae Transmitted from human to human

49. Chlamydial Pneumonia Symptoms: Mild respiratory illness common in young people; resembles mycoplasmal pneumonia Diagnosis: Serological tests Treatment: Tetracyclines

50. Q Fever Causative agent: Coxiella burnetii, Intracellular bacteria Reservoir: Large mammals Tick vector carries the bacteria Can be transmitted via unpasteurized milk

51. Coxiella burnetii, the Cause of Q Fever

52. Q Fever Symptoms: Mild respiratory disease lasting 1–2 weeks; occasional complications such as endocarditis occur Diagnosis: Growth in cell culture Treatment: Doxycycline and chloroquine

53. Melioidosis Causative agent: by Burkholderia pseudomallei; gram negative rod Reservoir: Soil Mainly in southeast Asia and northern Australia Symptoms: Pneumonia, or tissue abscesses and severe sepsis Diagnosis: Bacterial culture Treatment: Ceftazidime

54. Diseases in Focus: Common Bacterial Pneumonias A 27-year-old man with a history of asthma was hospitalized with a 4-day history of progressive cough and 2 days of spiking fevers. Gram-positive cocci in pairs were cultured from a blood sample. Can you identify infections that could cause these symptoms?

55. Viral Pneumonia Viral pneumonia occurs as a complication of influenza, measles, or chickenpox Viral etiology suspected if no other cause is determined

56. Respiratory Syncytial Virus (RSV) The most common viral respiratory disease in infants; 4500 deaths annually Causes cell fusion (syncytium) in cell culture Symptoms: Pneumonia in infants Diagnosis: Serological test for viruses and antibodies Treatment: Ribavirin, palivizumab

57. Influenza (Flu) Symptoms: Chills, fever, headache, and muscle aches No intestinal symptoms 1% mortality, very young and very old Treatment: Zanamivir and oseltamivir inhibit neuraminidase Prophylaxis: Multivalent vaccine (currently grown in Embryonated egg cultures

58. The Influenza Virus Hemagglutinin (HA) spikes used for attachment to host cells Neuraminidase (NA) spikes used to release virus from cell

59. The Influenza Virus Antigenic shift Probably due to genetic recombination between different strains infecting the same cell Process by which at least two different strains of a virus, combine to form a new subtype having a mixture of the surface antigens of the two original strains. Changes in HA and NA spikes so is the cause of recurring epidemics Antigenic shift, however, occurs only in influenzavirus A because it infects more than just humans

60. Antigenic drift Natural mutation over time of known strains Point mutations in genes encoding HA or NA spikes Antigenic shift is important as it is a pathway that viruses may follow to enter a new niche, and so should not be overlooked in the emergence of new viral pathogens. May involve only 1 amino acid Antigenic drift occurs in all types of influenza

61. Influenza Serotypes

62. Fungal Infections Fungal spores are easily inhaled; they may germinate in the lower respiratory tract. The incidence of fungal diseases has been increasing in recent years. The mycoses can be treated with amphotericin B.

63. Histoplasmosis Histoplasma capsulatum, dimorphic fungus Bird droppings provide nutrients, especially nitrogen, to the fungus Symptoms similar to tuberculosis (identify by microscopic exam of sputa & serologic tests)

64. Histoplasmosis Distribution

65. Coccidioidomycosis Causative agent: Coccidioides immitis (inhalation of arthroconidia) Reservoir: Desert soils of Southwest U.S. Symptoms: Fever, coughing, weight loss Diagnosis: Serological tests Treatment: Amphotericin B

66. The Life Cycle of Coccidioides immitis 

67. U.S. Endemic Area for Coccidioidomycosis

68. Pneumocystis Pneumonia Causative agent: Pneumocystis jirovecii , a parasite Reservoir: Unknown; possibly humans or soil Symptoms: Pneumonia Diagnosis: Microscopy Treatment: Trimethoprim Pneumocystis is opportunistic pathogen It usually does not cause disease, but can if the host’s resistance is low

70. Blastomycosis Causative agent: Blastomyces dermatitidis Reservoir: Soil in Mississippi valley area Symptoms: Abscesses; extensive tissue damage Diagnosis: Isolation of pathogen Treatment: Amphotericin B

71. Other Fungi Involved in Respiratory Disease Systemic Predisposing factors: Immunocompromised state Cancer Diabetes Aspergillus fumigatus Mucor Rhizopus

72. Diseases in Focus: Diseases of the Lower Respiratory System A worker was hospitalized for acute respiratory illness. He had been near a colony of bats. The mass was surgically removed. Microscopic examination of the mass revealed ovoid yeast cells. Can you identify infections that could cause these symptoms?