Legionella species

Background:

——————————————————————————
Atypical Organisms
——————————————————————————
>Chlamydophila pneumoniae
>Chlamydophila psittaci
>Coxiella burnetii
>Legionella species ( L. pneumophila) led
>Mycoplasma pneumonia

Legionella species

  • pathogenic group of gram negative bacterium. 
  • Common in many environments, including soil and aquatic systems, with at least 50 species identified.  
  • Requires the presence of cysteine and iron to grow and therefore does not grow on common blood agar media used for laboratory based total viable counts or on site dipslides.   
  • Many hospitals use the Legionella Urinary Antigen test for initial detection when Legionella pneumonia is suspected (results can be obtained in a matter of hours rather than the five days required for culture).   
  • L. pneumophila, causes Legionnaires Disease. L.longbeachae causes Pontiac Fever.

 

top of page

Legionella pneumophila:  

  • Thin, aerobic, pleomorphic, flagellated, non-spore forming, Gram-negative bacterium of the genus Legionella.
  • L. pneumophila is the primary human pathogenic bacterium in this group and is the causative agent of legionellosis or Legionnaires’ disease.
  • L. pneumophila is a gram-negative, non-encapsulated, aerobic bacillus with a single, polar flagellum often characterized as being a coccobacillus. It is aerobic and unable to hydrolyse gelatin or produce urease. It is also non-fermentative.
  • It is oxidase- and catalase-positive, and produces beta-lactamase.
  • L. pneumophila has a colony morphology that is gray-white with a textured, cut-glass appearance; it also requires cysteine and iron to thrive.
  • Legionella stains poorly with gram stain (due to its unique lipopolysaccharide-content), stains positive with silver, and is cultured on charcoal yeast extract with iron and cysteine.
  • Source: https://en.wikipedia.org/wiki/Legionella_pneumophila

top of page

Therapy:

Important considerations:  The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions.   Generally, the most common agents/regimens are listed first.  Total duriation of therapy is usually 7 to 10 days, however, for more severe cases or for immunosuppressed patients consider prolonging therapy for up to 3 weeks.

  1. Levofloxacin 750 mg IV/PO once daily
  2. Moxifloxacin 400mg orally/IV once daily
  3. Azithromycin 500mg oral/IV once daily.  Some references suggest giving 1 gram x 1  for 1st dose, then continue with 500mg daily.
  4. Doxycycline 100mg oral or IV twice daily
  5. Bactrim 8 to 10 mg/kg/day (based on trimethoprim component) IV divided in 2-4 doses.

Note: In severe disease consider adding Rifampin 300-450 mg  orally/IV q12h PLUS one antibiotic from above.

Disclaimer

The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgment. Neither GlobalRPh Inc. nor any other party involved in the preparation of this program shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user’s use of or reliance upon this material.PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER. Read the disclaimer