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Legionnaire's disease

Etiology: - Legionella pneumophila Epidemiology: - peak activity in warm, rainy, & humid conditions [9] - primarily affects older patients [9] - more common among cigarette smokers, immunocompromised patients, & patients with chronic lung disease [9] - 20% of Legionnaires' disease cases were probably or definitely acquired in healthcare facilities [8] - affects younger persons sharing hot tub [4] Clinical manifestations: 1) incubation period is 2-10 days 2) general a) high fever b) chills c) malaise 3) pulmonary a) non-productive cough (abrupt onset) b) hemoptysis (30%) c) dyspnea 4) gastrointestinal symptoms - nausea, diarrhea, abdominal pain 5) musculoskeletal a) arthralgia b) myalgia 6) headache 7) relative bradycardia 8) delirium Laboratory: 1) serum sodium: hyponatremia (50-70%) 2) serum phosphate: hypophosphatemia (50%) 3) complete blood count - leukocytosis > 10,000/mm3 (60%) - relative lymphopenia, 4) serum protein: proteinuria (20%) 5) serum AST increased (60%) 6) urine Legionella antigen testing for serogroup 1 - 1st line diagnostic test [9] - sensitivity 60-80%; specificity > 99% - remains positive for days after administration of antibiotics 7) Legionella DNA testing may increase diagnostic yield [6] 8) sputum gram stain - faintly gram-negative bacillus - difficult to detect by Gram stain [9] 9) sputum culture - does not grow on routine microbiologic medium - requires buffered charcoal yeast extract agar for growth & isolation - identification from culture requires 3-5 days [9] 10) see Legionella for other diagnostic laboratory studies 11) see ARUP consult [6] Radiology: (Chest X-ray) 1) diffuse, patchy infiltrates 2) ill-defined nodules 3) bilateral lobar-segmental involvement Management: 1) antimicrobial therapy a) macrolide - azithromycin [9] - erythromycin - 500 mg PO every 6 hours for mild cases - 1 g IV every 6 hours for severe cases - continue therapy for 21 days - Rifampin 600 mg PO QD may be synergistic b) respiratory fluoroquinolone - levofloxacin as effective as macrolide [5] c) alternative antibiotics - doxycycline - Bactrim 2) Legionella endocarditis - valve replacement - 3-12 months of antibiotic therapy

Related

Legionella pneumophila

General

legionellosis bacterial pneumonia

References

  1. Manual of Medical Therapeutics, 28th edition, Ewald & McKenzie (eds) Little, Brown & Co, 1995, pg 302
  2. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 228-29
  3. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 797
  4. Medical Knowledge Self Assessment Program (MKSAP) 11, 18, 19. American College of Physicians, Philadelphia 1998, 2018, 2021.
  5. Journal Watch 25(8):63-64, 2005 - Blazquez Garrido RM, Espinosa Parra FJ, Alemany Frances L, Ramos Guevara RM, Sanchez-Nieto JM, Segovia Hernandez M, Serrano Martinez JA, Huerta FH. Antimicrobial chemotherapy for legionnaires disease: levofloxacin versus macrolides. Clin Infect Dis. 2005 Mar 15;40(6):800-6. Epub 2005 Feb 17. PMID: 15736011
  6. Murdoch DR et al. Impact of routine systematic polymerase chain reaction testing on case finding for Legionnaires' disease: A pre - post comparison study. Clin Infect Dis 2013 Nov 1; 57:1275 PMID: 23899682 http://cid.oxfordjournals.org/content/57/9/1275
  7. ARUP Consult: Legionella pneumophila The Physician's Guide to Laboratory Test Selection & Interpretation https://www.arupconsult.com/content/legionella-pneumophila
  8. Soda EA, Barskey AE, Shah PP, et al. Vital Signs: Health Care-Associated Legionnaires' Disease Surveillance Data from 20 States and a Large Metropolitan Area - United States, 2015. MMWR Morb Mortal Wkly Rep . ePub: 6 June 2017. https://www.cdc.gov/mmwr/volumes/66/wr/mm6622e1.htm
  9. Rothaus C An Unexpected Expectoration. NEJM Resident 360. Feb 28, 2018 https://resident360.nejm.org/content_items/an-unexpected-expectoration
  10. Cunha BA. Legionnaires' disease: clinical differentiation from typical and other atypical pneumonias. Infect Dis Clin North Am. 2010 Mar;24(1):73-105. Review. PMID: 20171547
  11. Centers for Disease Control & Prevention (CDC) Legionella (Legionnaires' Disease and Pontiac Fever) https://www.cdc.gov/legionella/index.html - Centers for Disease Control & Prevention (CDC) Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings. A Practical Guide to Implementing Industry Standards. https://www.cdc.gov/legionella/maintenance/wmp-toolkit.html