Blt19 14 Jan 09 A Prof Raymond Lin Respiratory Tract Infections

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Blt19 14 Jan 09 A Prof Raymond Lin Respiratory Tract Infections

  1. 1. Respiratory Tract Infections Associate Professor Raymond Lin Head, Clinical Microbiology BLT18/2008
  2. 3. <ul><li>The upper and lower respiratory tract is a continuum, along with organisms may track </li></ul><ul><li>Defence mechanisms </li></ul><ul><ul><li>Anatomical e.g. cilia </li></ul></ul><ul><ul><li>Surface defences at epithelium: lysozymes, IgA, phagocytes </li></ul></ul><ul><ul><li>Colonization resistance </li></ul></ul>
  3. 4. <ul><li>Types of pathogens </li></ul><ul><ul><li>Infect healthy persons </li></ul></ul><ul><ul><li>Infect those with poor defence “opportunistic” </li></ul></ul><ul><ul><li>Use respiratory route to spread to rest of body </li></ul></ul>
  4. 5. Normal oropharyngeal flora <ul><li>viridans streptococci, Neisseria spp., Moraxella catarrhalis, diphtheroids, anaerobes </li></ul><ul><li>S. pneumoniae, Haemophilus influenzae, Haemophilus spp. </li></ul><ul><li>“ colonization resistance” </li></ul><ul><li>Flora gets replaced with disease, antibiotics, devices, hospital stay </li></ul><ul><li>May track to lower respiratory tract “aspiration” </li></ul>
  5. 7. Pathogens <ul><li>Common respiratory viruses “URTI” </li></ul><ul><ul><li>Rhinovirus, influenza, parainfluenza, adenovirus, respiratory syncytial virus (RSV) </li></ul></ul><ul><ul><li>Enterovirus, hu coronaviruses, hu metapneumovirus </li></ul></ul>
  6. 8. <ul><li>Pharyngitis (“sore throat”) </li></ul><ul><ul><li>Group A streptococcus ( S. pyogenes ) </li></ul></ul><ul><ul><li>Viruses </li></ul></ul>
  7. 9. Upper respiratory cavity infections <ul><li>Acute bacterial sinusitis </li></ul><ul><li>Acute suppurative otitis media </li></ul><ul><li>Common bacteria </li></ul><ul><ul><li>Streptococcus pneumoniae </li></ul></ul><ul><ul><li>Haemophilus influenzae </li></ul></ul><ul><ul><li>Moraxella catarrhalis </li></ul></ul>
  8. 10. Eustachian tube in infants – wider & horizontal
  9. 13. Otitis externa <ul><li>External ear infected </li></ul><ul><ul><li>Pseudomonas aeruginosa </li></ul></ul><ul><ul><li>Aspergillus niger </li></ul></ul>
  10. 14. Otitis externa
  11. 15. sinusitis
  12. 16. “ CROUP” laryngo-tracheo-bronchitis hoarse voice, barking cough severe cases - airway obstruction Laryngitis Parainfluenza viruses
  13. 17. Bronchitis Bronchiolitis Bronchiectasis
  14. 18. Pleural effusion Empyema Pneumothorax
  15. 19. Pneumonia <ul><li>Pathogen varies with age, underlying disease </li></ul><ul><li>Hospital vs. community-acquired </li></ul><ul><li>Hospital </li></ul><ul><ul><li>Immunocompromised </li></ul></ul><ul><ul><li>ICU - ventilator </li></ul></ul><ul><ul><li>Antibiotics </li></ul></ul><ul><ul><li>Multi-resistant bacteria </li></ul></ul><ul><ul><ul><li>MRSA, Acinetobacter baumannii </li></ul></ul></ul>
  16. 20. Pneumonia - pathogens <ul><li>Streptococcus pneumoniae (“pneumococcus”) </li></ul><ul><li>Haemophilus influenzae </li></ul><ul><li>Mycoplasma pneumoniae </li></ul><ul><li>Chlamydia pneumoniae </li></ul><ul><li>Viruses: adenovirus, influenza </li></ul>Viruses more important in children.
  17. 21. Pneumonia <ul><li>Environment </li></ul><ul><ul><li>E.g. legionella </li></ul></ul><ul><ul><li>E.g. melioidosis </li></ul></ul>
  18. 22. Cooling tower - a possible source of Legionella infection
  19. 23. <ul><li>Pets, animals e.g. </li></ul><ul><ul><li>Q fever </li></ul></ul><ul><ul><li>Psittacosis </li></ul></ul><ul><ul><li>hantavirus pulmonary syndrome </li></ul></ul><ul><ul><li>“ zoonosis” </li></ul></ul>
  20. 24. Pneumonia – immunocompromised patients <ul><li>Examples: transplant patients, neutropenic, ICU </li></ul><ul><ul><li>Unusual organisms not affecting normal adults </li></ul></ul><ul><ul><li>E.g. Pneumocystis jiroveci (P. carinii) , cytomegalovirus, aspergillus </li></ul></ul>
  21. 25. Hospital pathogens
  22. 26. Laboratory approaches <ul><li>Sputum culture and gram stain </li></ul><ul><li>Respiratory virus culture/ IF/ PCR </li></ul><ul><li>Blood culture </li></ul><ul><li>Serology </li></ul><ul><ul><li>E.g. mycoplasma, legionella </li></ul></ul>
  23. 27. Investigations <ul><li>Sputum culture </li></ul><ul><ul><li>Easy to collect and do </li></ul></ul><ul><ul><li>May be contaminated with oropharyngeal flora – check epithelial cells on Gram stain </li></ul></ul><ul><ul><li>Some bacteria are non-cultivable </li></ul></ul>
  24. 28. Investigations <ul><li>Blood culture </li></ul><ul><ul><li>More definite proof of causative organism </li></ul></ul><ul><ul><li>Not sensitive </li></ul></ul><ul><ul><li>Some bacteria don’t grow in usual media e.g. Mycoplasma pneumoniae </li></ul></ul><ul><li>Serology </li></ul><ul><ul><li>Host response; good if specific enough </li></ul></ul><ul><ul><li>Delayed result; cross-reactivity; background positives </li></ul></ul><ul><ul><li>E.g. legionella, mycoplasma </li></ul></ul>
  25. 29. Investigations <ul><li>Viruses </li></ul><ul><ul><li>Antigen detection e.g. IF – rapid </li></ul></ul><ul><ul><li>Virus isolation – slow – can find new viruses </li></ul></ul><ul><ul><li>PCR – many agents to look for </li></ul></ul><ul><ul><li>Serology – not usually useful – need paired titre </li></ul></ul>
  26. 31. Sputum specimen composed of saliva and purulent material
  27. 35. Organisms that can be missed in a sputum BAL - Legionella - Pneumocystis jiroveci Respiratory Tract Specimens
  28. 42. Mycobacteria TB bacillus Mycobacterium tuberculosis Non-TB bacilli many species M leprae, M avium, M kansasi etc
  29. 43. TB bacillus Mycobacterium tuberculosis Acid fast bacilli (AFB) when stained with ZN technique Normal habitat infected humans infected cattle Pathogenicity about 10 million people affected 3 million deaths Spread droplets > lungs > lymph / blood > kidney, bone, joints
  30. 44. Mycobacterium tuberculosis <ul><li>Primary infection </li></ul><ul><li>Latent infection – no symptoms </li></ul><ul><li>Dormancy – remains in lymph nodes for many years </li></ul><ul><li>Reactivation disease – when elderly or immunocompromised </li></ul>
  31. 45. Tuberculosis - diagnosis <ul><li>Clinical symptoms: cough, night sweats, loss of weight </li></ul><ul><li>CXR </li></ul><ul><li>Lab tests </li></ul>
  32. 46. Tests for tuberculosis <ul><li>Sputum or BAL or gastric aspirate </li></ul><ul><ul><li>Acid-fast smear (“AFB” smear) </li></ul></ul><ul><ul><li>Molecular detection e.g. MTD, PCR </li></ul></ul><ul><ul><li>Culture e.g. L-J media, broth (MGIT, BacTAlert) </li></ul></ul><ul><li>Immunity or exposure </li></ul><ul><ul><li>Mantoux test </li></ul></ul><ul><ul><li>Interferon gamma tests </li></ul></ul><ul><ul><ul><li>Quantiferon </li></ul></ul></ul><ul><ul><ul><li>TBSpot (ELISPOT) </li></ul></ul></ul>
  33. 48. Bordetella pertussis (“whooping cough”) <ul><li>Affects mainly children, milder symptoms in adults </li></ul><ul><li>Vaccine preventable (part of childhood DPT immunization) </li></ul><ul><li>Clinical features: coughing fits and vomiting, inspiratory “whoop”, pneumonia </li></ul><ul><li>Occasional cases in children; epidemics when immunization low </li></ul>
  34. 49. pertussis <ul><li>Laboratory workup </li></ul><ul><ul><li>Direct IF </li></ul></ul><ul><ul><li>Culture : Bordet-Gengou media </li></ul></ul><ul><ul><li>PCR : most sensitive test now </li></ul></ul><ul><ul><li>Serology : IgA, IgM – not so reliable – not used in Singapore </li></ul></ul>
  35. 50. Summary <ul><li>Be able to </li></ul><ul><ul><li>List the main pathogens for each site e.g. pneumonia, sinusitis, otitis media, URTI </li></ul></ul><ul><ul><li>Outline the diagnostic approaches with examples; limitations of each </li></ul></ul><ul><ul><li>TB: know some basic concepts </li></ul></ul>

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