Is Legionella anisa in the hospital water a concern?

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Is Legionella anisa in the hospital water a concern? 

Legionella anisa is a fairly common environmental species. In a recent survey we have found that about 20% of hospitals in the US are colonized; the number of reported cases of infection is extremely low. There is a reported outbreak of non-pneumonic legionellosis (“Pontiac Fever”) due to L. anisa occurring in an automobile plant due to contaminated, aerosol generating equipment. There is limited laboratory evidence to suggest that L. anisa may be somewhat less pathogenic that L. pneumophila, at least based on an ability to infect mammalian cells.

The risk of disease after exposure to environmental L. anisa by healthy people, or the general hospital patient population is exceedingly low. It might be advisable, however, to protect highly immunocompromised patients, such as transplant patients, patients on high dose corticosteroids, from exposure.

Key references:

  1. La Scola B, Mezi L, Weiller PJ, Raoult D. Isolation of Legionella anisa using an amoebic coculture procedure. J Clin Microbiol. 2001 Jan;39(1):365-6. PMID: 11136802.
  2. Fields BS, Barbaree JM, Sanden GN, Morrill WE. Virulence of a Legionella anisa strain associated with Pontiac fever: an evaluation using protozoan, cell culture, and guinea pig models. Infect Immun. 1990 Sep;58(9):3139-42. PMID: 2117580.
  3. Fenstersheib MD, Miller M, Diggins C, Liska S, Detwiler L, Werner SB, Lindquist D, Thacker WL, Benson RF. Outbreak of Pontiac fever due to Legionella anisa. Lancet. 1990 Jul 7;336(8706):35-7. PMID: 1973219.
  4. Fallon RJ, Stack BH. Legionnaires’ disease due to Legionella anisa. J Infect. 1990 May;20(3):227-9 PMID:2341733.
  5. Thacker WL, Benson RF, Hawes L, Mayberry WR, Brenner DJ. Characterization of a Legionella anisa strain isolated from a patient with pneumonia. J Clin Microbiol. 1990 Jan;28(1):122-3. PMID: 2405005.
  6. Bornstein N, Mercatello A, Marmet D, Surgot M, Deveaux Y, Fleurette J. Pleural infection caused by Legionella anisa. J Clin Microbiol. 1989 Sep; 27(9):2100-1. PMID: 2778073.