Respiratory Infections

1. Respiratory Infections Chapter 5

2. Infections of the Respiratory tract • Most common entry point for infections • Upper respiratory tract • nose, nasal cavity, sinuses, mouth, throat • Lower respiratory tract • Trachea, bronchi, bronchioles, and alveoli in the lungs

3. Protective Mechanisms Normal flora: Commensal organisms • Limited to the upper tract • Mostly Gram positive or anaeorbic • Microbial antagonist (competition)

4. Protective Mechanisms Clearance of particles and organisms from the respiratory tract Cilia and microvilli move particles up to the throat  where they are swallowed. Alveolar macrophages migrate and engulf particles and bacteria in the alveoli deep in the lungs.

5. Other Protective Mechanisms • Nasal hair, nasal turbinates • Mucus • Involuntary responses (coughing) • Secretory IgA • Immune cells

6. Response towards foreign particles • Ventilatory flow • Cough • Mucociliary clearance mechanisms • Mucosal immune system

7. Selected Bacterial Infections Pharyngitis Group A Strep - Streptococcus pyogenes (Many viruses also cause this) Pneumonia - Streptococcus pneumoniae Diphtheria - Corynebacterium diphtheriae Tuberculosis - Mycobacterium tuberculosis Whooping cough - Bordetella pertussis

8. Disease of upper respiratory tract Pharyngitis and related infections Diptheria

9. Examples of common infections • Laryngitis • Streptococcal Pharyngitis • Scarlet Fever • Sinusitis • Diptheria • Otitis media • Advance stages – bacterial superinfection, mastoiditis, meningitis and brain abscess

10. Laryngitis • Most commomly upper respiratory viruses • Diphtheria - C. diphtheriae produces a cytotoxic exotoxin causing tissues necrosis at site of infection with associated acute inflammation. Membrane may narrow airway and/ or slough off (asphyxiation)

11. Streptococcal Pharyngitis (Strep Throat) • Caused by group A beta-hemolytic streptococci of S.pyogenes • Also causing impetigo, erysipelas and endocarditis on skin • Causing inflammation of the mucous membrane and fever; tonsilitis and otitis media may also occur • Rapid diagnosis using enzyme immunoassays.

12. Strep Throat • Fever • Tonsillitis • Enlarged lymph nodes • Middle-ear infection

13. Streptococcus pyogenes • Gram positive streptococci • Carried and transmitted from the throat • In Respiratory secretions

14. Group A Strep • Capsule -resistant to phagocytosis • Enzymes damage host cells • M protein adhesin The M protein has many antigenic varieties and thus, different strain of S.pyogenes cause repeat infections

15. Scarlet fever • Caused by S. pyogenes producing erythrogenic toxin • The bacteriophage disturb the normal characterristic of bacteria that involving genetic mutation • Also associate with pharyngitis and skin infection that caused by the same bacteria • It is nowadays become mild and rare disease

16. Scarlet Fever Caused by Erythrogenic Toxin secreted by S. pyogenes

17. Scarlet Fever • The erythrogenic toxin is coded by a gene lysogenic bacteriophage within the genome of S. pyogenes • Rash is an inflammatory reaction to the toxin

18. Sinusitis • Commonly caused by S. pneumoniae, Moraxella catarrhalis / H. influezae • can also caused by S. aureus/ S.pyogenes • The sinus cavity will swelling and prevent drainage that resulting pressure and severe pain • Pt usually produce mucus, bacteria and phagocytic cells that collect in the sinuses

19. Cont. • Chronic stages caused by Bacteriodes • Mostly occur above the root of upper teeth which infection derived from oral cavity • Treatment by applying moist heat on particular area / drop an ephedrine / raise head to help drainage • Best antibiotic - penicillin

20. Dipteria • Until 1935, it leading infection to children of US • Vaccine used for children is DTaP vaccine • Diptheria Toxoid antibodies Production (DTaP) • Spread thru air bourne and resistant towards drying • The greyish toungue contain fibrin, dead tissues and bacterial cells that block the air passage • 0.01mg of highly virulence toxin - fatal

21. Corynebacterium diphtheriae • Aerobic Gram + bacillus • Toxin inhibits protein synthesis of cells to which it binds • Destroyed cells and WBC form "pseudomembrane" which blocks airways

22. Severe stage

23. Corynebacterium diphtheriae • To produce toxin, C. dithpheriae must be infected with a bacteriophage carrying the toxin gene

24. An “AB” toxin • B = binding subunit • A = active subunit which binds to and inhibits a eucaryotic ribosomal translation factor • Vaccine is diphtheria toxoid

25. Otitis media • Uncomfortable common cold, that infecting nose or throat (otitis media) • 85% infecting children below 3 yrs old • Best antibiotic from penicillin group • The antibiotics used were just reduction the duration of infection

26. causes • S. pneumoniae • H. influenzae • S.pyogene • Moraxella catarrhalis • S.aureus

27. Infected Middle Ear(otitis media)

28. Diseases of lower respiratory tract Whooping cough Tuberculosis Pneumonia

29. Whooping cough

30. Bordetella pertussis • Gram negative cocco-bacillus • Capsule • Adherence to ciliated cells • Pertussis toxin is A-B toxin

31. Pertussis (Whooping Cough) • Cough • Violent coughing followed by whooping sound • Vaccine – it is made of purified components • Not lifelong immunity – adult carriers

32. Pneumonia

33. Bacterial Pneumonia Bacterial, viral or fungal infection can cause Inflammation of the lung with fluid filled alveoli

34. Community Acquired Pneumonia • Infection of the lung parenchyma in a person who is not hospitalized or living in a long-term care facility for ≥ 2 weeks • Most common pathogen = S. pneumo(60-70% of CAP cases)

35. “Nosocomial” Pneumonia • Hospital-acquired pneumonia (HAP) • Occurs 48 hours or more after admission, which was not incubating at the time of admission • Ventilator-associated pneumonia (VAP) • Arises more than 48-72 hours after endotracheal intubation

36. “Nosocomial” Pneumonia • Healthcare-associated pneumonia (HCAP) • Patients who were hospitalized in an acute care hospital for two or more days within 90 days of the infection; resided in a nursing home or LTC facility; received recent IV abx, chemotherapy, or wound care within the past 30 days of the current infection; or attended a hospital or hemodialysisclinic

37. Pathogenesis • Inhalation, aspiration and hematogenous spread are the 3 main mechanisms by which bacteria reaches the lungs • Primary inhalation: when organisms bypass normal respiratory defense mechanisms or when the Pt inhales aerobic GN organisms that colonize the upper respiratory tract or respiratory support equipment

38. Pathogenesis • Aspiration: occurs when the Pt aspirates colonized upper respiratory tract secretions • Stomach: reservoir of GNR that can ascend, colonizing the respiratory tract. • Hematogenous: originate from a distant source and reach the lungs via the blood stream.

39. Pathogens • CAP usually caused by a single organism • Even with extensive diagnostic testing, most investigators cannot identify a specific etiology for CAP in ≥ 50% of patients. • In those identified, S. pneumo is causative pathogen 60-70% of the time

40. Streptococcus pneumonia • Most common cause of CAP • Gram positive diplococci • “Typical” symptoms (e.g. malaise, shaking chills, fever, rusty sputum, pleuritic hest pain, cough) • Lobar infiltrate on CXR • Suppressed host • 25% bacteremic

41. Pneumonia Atypical Pneumonia • #2 cause (especially in younger population) • Commonly associated with milder Sx’s: subacute onset, non-productive cough, no focal infiltrate on CXR • Mycoplasma: younger Pts, extra-pulm Sx’s (anemia, rashes), headache, sore throat • Chlamydia: year round, URI Sx, sore throat • Legionella: higher mortality rate, water-borne outbreaks, hyponatremia, diarrhea

42. Viral Pneumonia • More common cause in children • RSV, influenza, parainfluenza • Influenza most important viral cause in adults, especially during winter months • Post-influenza pneumonia (secondary bacterial infection) • S. pneumo, Staph aureus

43. Other bacteria • Anaerobes • Aspiration-prone Pt, putrid sputum, dental disease • Gram negative • Klebsiella - alcoholics • Branhamella catarrhalis - sinus disease, otitis, COPD • H. influenza • Staphylococcus aureus • IVDU, skin disease, foreign bodies (catheters, prosthetic joints) prior viral pneumonia

44. Streptococcus pneumoniae • Pneumococcus • Encapsulated • Often secondary infection following influenza virus

45. Bacterial Pneumonia • Streptococcus pneumoniae • 2/3 of all pneumonia • Risk Factors- old age, season, underlying • viral infection, diabetes, alcohol and narcotic use • Variable capsular antigen • Purified component (capsule) vaccine • Others that cause pneumonia: • Mycoplasma pneumoniae • Legionella pneumophila

46. Tuberculosis

47. Mycobacterium tuberculosis • Acid-fast bacillus – complex cell wall with “cord factor” • Causes TB: lungs bones, other organs • Airborne, (milk, v. rare)

48. Mycobacterium tuberculosis • Thick lipid coat of “Mycolic fatty acids” • Grows very slowly • Resists killing by macrophages and grows in them

49. Tubercule formation A tubercle in the lung is a “granuloma” consisting of a central core of TB bacteria inside an enlarged macrophage, and an outer wall of fibroblasts, lymphocytes, and neutrophils

50. Tuberculosis • Primary • Lung tubercles, caseous, tuberculin skin reaction • Secondary (reactivation) • Consumption: Coughing and chronic weight loss • Dissemination • Extrapulmonary TB (lymph nodes, kidneys, bones, genital tract, brain, meninges)