Compost and Legionella longbeachae: an emerging infection?

Abstract

Human disease caused by Legionella species is dominated by Legionella pneumophila, the main causative agent in cases of Legionnaires' disease. However, other species are known to cause infection, for example, Legionella longbeachae causes an equivalent number of cases of disease as L. pneumophila in Australia and New Zealand. Infection with L. longbeachae is commonly associated with exposure to composts and potting soils, and cases of infection with this organism have been increasing in Europe over the past ten years. The increase in incidence may be linked to factors such as increased awareness of clinical presentation, or due to changing formulation of growing media, although it should be noted that the presence of Legionella species in growing media does not correlate with the number of cases currently seen. This is likely due to the variables associated with infection, for example, host factors such as smoking or underlying health conditions, or difference in growing media storage or climate, especially warm humid conditions, which may affect survival and growth of these organisms in the growing media environment. There are numerous unknowns in this area and collaboration between growing media manufacturers and researchers, as well as more awareness among diagnosing clinicians, laboratory staff and the general public is necessary to reduce risk. More research is needed before definitive conclusions can be drawn: L. pneumophila research currently dominates the field and it is likely that the overreliance on diagnostic techniques such as the urinary antigen test, which is specific for L. pneumophila Sg 1, is detrimental to the diagnosis of L. longbeachae infection.

Healthcare-Associated Legionnaires’ Disease, Europe, 2008−2017

“…The association of HCA LD with less virulent strains probably reflects patient demographic variables; immunocompromised patients might be more highly concentrated in healthcare facilities than in the general community. Although non-L. pneumophila species caused only a few cases, the proportion of cases caused by those species (except for L. longbeachae, which only causes community-acquired LD and is frequently associated with exposure to composts and potting soils [26]) was higher in patients with HCA than community-acquired LD. Patients with non-L. pneumophila infections might be more likely to be immunocompromised (27).…”

Legionellen-Infektionsprävention: extrem teuer und wenig effektiv

“…Weltweit, v. a. in Australien, aber auch in Europa (Schottland, Niederlande), werden zunehmend Fälle von Legionärskrankheit registriert, die durch die Art L. longbeachae verursacht wurden [9]. Die Infektionsquelle war in diesen Fällen der Umgang mit Kompost und Pflanzenerde [10,11]. Eine niederländische Arbeitsgruppe fand allerdings auch L. pneumophila der Serogruppe 1-15 in mehreren Proben von Kompost, der in insgesamt 12 % Legionellen enthielt [10].…”

The Flagellar Regulon of Legionella—A Review

“…Known natural hosts are protozoa, especially free-living amoebae: Acanthamoeba spp., Naegleria spp., or Hartmanella vermiformis (Barbaree et al, 1986 ; Rowbotham, 1986 ; Fields, 1996 ; Atlas, 1999 ; Fields et al, 2002 ; Greub and Raoult, 2004 ; Abdel-Nour et al, 2013 ; Richards et al, 2013 ; Cateau et al, 2014 ). Accordingly, in general, Legionella species are prevalent inhabitants of soil, mud and above all of aquatic environments (Fliermans et al, 1981 ; Fields, 1996 ; Atlas, 1999 ; Gomez-Valero et al, 2009 ; Declerck, 2010 ; Schalk et al, 2014 ; Currie and Beattie, 2015 ). The ability of L. pneumophila to grow within biofilms made by Klebsiella pneumoniae or Pseudomonas aeruginosa in aquatic or wet environments raised questions about their host-free persistence (Stewart et al, 2012 ).…”