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Atypical Pneumonia

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  1. BY Annerie Hattingh 26/08/09 AtypicalPneumonia

  2. Introduction: Pneumonia caused by atypical pathogens Typical pathogens usually includes: - Strep. pneumonia - Haemophilus pneumonia - Klebsiella pneumonia Does not respond to the usual antibiotics Causes a milder form of pneumonia (hence the term “walking pneumonia”) Characterized by a more drawn out coarse of symptoms

  3. Legionella + SARS are exceptions to the above – both can be very severe infections Typical pneumonia can come on more quickly + with more severe early sx The arbitrary classification of typical vs. atypical pneumonia is of limited clinical value Literature now shows that a primary pathogen may co-exist with a secondary one, further blurring this distinction Introduction:

  4. Introduction: Causes: “Classical” atypical pneumonias: 1.) Mycoplasma pneumonia 2.) Chlamydia pneumonia 3.) Legionella pneumonia

  5. Introduction: Causes: Other micro-organisms that cause similar patterns of presentation: 1.) Chlamydia psittaci (exposure to birds) 2.) Coxiella burnetti (presenting as Q fever) 3.) Viral pneumonias - Influenza A - SARS - RSV - Adenoviridae - Varicella pneumonitis

  6. Epidemiology: It is thought that the 3 main atypical pathogens might be implicated in up to 40% of CAP The precise incidence is not known Often not identified in clinical practice due to lack of readily available, reliable standardized tests to confirm dx By age 20, 50% of people in the USA have detectable levels of Antibodies to Chlamydia pneumonia

  7. Risk Factors: Mycoplasma + Chlamydia spread by person-to-person contact - spread most common in closed populations e.g. schools, offices + military barracks Legionellae found most commonly in fresh water + man-made H2O systems

  8. Risk Factors: - sources of contaminated H2O includes: * showers * condensers * whirlpools * cooling towers * respiratory equipment * air conditioning systems

  9. Risk Factors: Other risk factors include: - young, healthy people - cigarette smoking - lung disease (like COPD) - weakened immune system (e.g. chronic steroid use or HIV)

  10. Presentation: Mycoplasma pneumonia: Gram neg bacteria with no true cell wall Frequent cause of CAP in adults + children Prevalence in adults with pneumonia 2 – 30% Tends to be endemic, occurring @ 4-7yr intervals

  11. Presentation: Mycoplasma pneumonia: Clinical Features: Symptomatic / asymp Gradual onset (over few days – weeks) Prodrome of “flu-like” symptoms

  12. Presentation: Mycoplasma pneumonia: Clinical Features: Including: - headache - malaise - fever - non prod. Cough - sore throat

  13. Presentation: Mycoplasma pneumonia: Clinical Features: Objective AbN on physical exam are minimal in contrast to the pt’s reported symptoms Present like many of common viral illnesses BUT persistence + progression of sx help to mark it out

  14. Presentation: Mycoplasma pneumonia: Extrapulm. Manifestations/Complications: Can involve: CNS, Blood, Skin, CVS, Joints, GIT

  15. Presentation: Mycoplasma pneumonia: Extrapulm. Manifestations/Complications: Neurological compl. Aseptic meningitis Cerebellar ataxia Transverse myelitis Peripheral neuropathy

  16. Presentation: Mycoplasma pneumonia: Extrapulm. Manifestations/Complications: Neurological manifestations are infrequent Usually found in kids, if seen Associated with increased morbidity + mortality Antecedent resp. infection not always present

  17. Presentation: Mycoplasma pneumonia: Extrapulm. Manifestations/Complications: Hematological compl. Hemolytic anemia IgM antibodies to erythrocyte membrane I antigen are present Produces a cold agglutinin response that leads to hemolysis

  18. Presentation: Mycoplasma pneumonia: Extrapulm. Manifestations/Complications: Dermatological compl. Include rashes such as: Erythema multiforme Erythema nodosum Urticaria

  19. Presentation: Mycoplasma pneumonia: Extrapulm. Manifestations/Complications: Cardiac involvement: Pericarditis Myocarditis

  20. Presentation: Mycoplasma pneumonia: Extrapulm. Manifestations/Complications: Joint involvent: (occationately described) Arthralgia Arthritis

  21. Presentation: Mycoplasma pneumonia: Extrapulm. Manifestations/Complications: GIT symptoms: N + V Diarrhea Pancreatitis (rarely)

  22. Presentation: Chlamydia: Genus Chlamydia includes 3 species that infect humans: - C. psittaci - C. trachomatis - C. pneumonia Small, coccoid, Gram neg bacteria that resemble rickettsiae

  23. Presentation: Chlamydia: Chlamydia trachomatis - seen in newborn infants during delivery - has been ass. with pneumonia in adults

  24. Presentation: Chlamydia: Chlamydia psittaci: Ornithosis is a systemic infection often acc. by pneumonia Common in birds + some domestic animals Pet shop employees + poultry workers @ risk Other systems involved: CNS (meningoencephalitis) + CVS (cult. neg. endocarditis)

  25. Presentation: Chlamydia pneumonia: Prevalence varies by yr + geographic setting Causes 5-15% of all CAP Repeat infection is common Gradual onset which may show improvement before worsening again Incubation 3-4 weeks Initial non-specific URTI Sx lead to bronchitic/ pneumonic features

  26. Presentation: Chlamydia pneumonia: Most infected remains quite well + asymptomatic Can cause prolonged, acute bronchitis with prod. cough Hoarseness + headache are common features Fever relatively uncommon Sx may drag on for weeks/months despite course of appropriate antibiotics

  27. Presentation: Chlamydia pneumonia: Clinical severity usually caused by a secondary pathogen or co-existing illness e.g. diabetes Complications: Sinusitis, otitis media New onset asthma after acute infection Endocarditis, myocarditis

  28. Presentation: Legionella pneumonia: Aerobic, motile, non-encapsulated, Gram neg bacilli Tends to be the most severe of the atypical pneumonias Focal outbreaks centered around poorly maintained air conditioning / humidification systems Incubation 2-10 days Initial mild headache, myalgia leading to fever, chills + rigors

  29. Presentation: Legionella pneumonia: Minimally prod. cough Dyspnoea, pleuritic pain + hemoptysis are not uncommon Extra pulmonary legionellosis is rare but can be severe CVS most common extrapulm. site causing myocarditis, pericarditis + endocarditis Also pancreatitis, peritonitis, glomerulonephritis + focal neurological deficit

  30. Diagnosis: CXR findings are usually non-specific and difficult to distinguish from other pneumonias Chest signs on examination minimal Rx of suspected atypical pneumonias should be empirical Cultures + serologic tests are not routinely available in laboratories

  31. Diagnosis: A 53yr old patient with severe Legionella pneumonia. CXR shows dense consolidation in both lower lobes.

  32. Diagnosis: A 40yr old patient with Chlamydia pneumonia. CXR shows multifocal, patchy consolidation in the right upper, middle and lower lobes.

  33. Diagnosis: A 38yr old patient with Mycoplasma pneumonia. CXR shows a vague, ill defined opacity in the left lower lobe.

  34. Management: Severe cases should be admitted Atypical pneumonias usually Rx as for other CAP, at least initially No evidence that routinely giving antibiotics active against atypical organisms leads to better outcomes in non-severe CAP

  35. Management: Macrolides, such as Erythromycin, Clarithromycin + Azithromycin have been shown to be effective in the Rx of all 3 organisms Erythromycin tends to be less well tolerated + only few trails demonstrates its efficacy in the Rx of Legionella Severe Legionella infections may require rifampicin + a macrolide Tetracycline, Doxycycline + Fluoroquinolones are also effective Recommened duration of therapy usually 2-3 weeks


  37. References: Shakeel Amanullah: Atypical Bacterial Pneumonia; eMed. March 2008. Atypical Pneumonias; Jan. 2007. Encyclopedia – Atypical Pneumonia (Mycoplasma and Viral) (Walking Pneumonia); May 2008. Rosen’s Emergency Medicine Online: Community Acquired Pneumonia