UMEM Educational Pearls

Legionella is an important cause of community-acquired pneumonia. It ranks among the three most common causes of severe CAP leading to ICU admission and carries a high mortality rate – up to 33%. Resulting from inhalation of aerosols containing Legionella species and subsequent lung infection, it is often associated with contaminated air conditioning systems, and other hot and cold water systems.

 

Recommended antibiotic regimens include a fluoroquinolone, either in monotherapy or combined with a macrolide (typically Levaquin or Azithromycin).

 

A retrospective, observational study published in the Journal of Antimicrobial Chemotherapy in 2017 looked at 211 patients admitted to the ICU with confirmed severe legionella pneumonia treated with a fluoroquinolone vs a macrolide and monotherapy vs combination therapy. Combination therapy included fluoroquinolone + macrolide, fluoroquinolone + rifampicin, or macrolide + rifampicin.

 

Of these 211 cases, 146 (69%) developed ARDS and 54 (26%) died in the ICU. Mortality was lower in the fluoroquinolone-based group (21%) than in the non-fluoroquinolone based group (39%), and in the combination therapy group (20%) than in the monotherapy group (34%). In a multivariable analysis, fluoroquinolone-based therapy, but not combination therapy was associated with a reduced risk of mortality (HR 0.41).

 

 

Take Home Points:

-Remember, our usual blanket coverage with vanc + zosyn in the ED does not cover atypicals!

-Consider Levaquin instead of Azithro if there is clinical concern for Legionella PNA

           -hyponatremia, abnormal LFTs may be clues in the appropriate context

 

 

 

References

Cecchini J, Tuffet S, Sonneville R, et al. Antimicrobial strategy for severe community-acquired legionnaires’ disease: a multicentre retrospective observational study. J Antimicrob Chemother. 2017;72(5):1502-1509. doi:10.1093/jac/dkx007.