Presence and Persistence of Viable, Clinically Relevant Legionella pneumophila Bacteria in Garden Soil in the Netherlands

Abstract

Garden soils were investigated as reservoirs and potential sources of pathogenic Legionella bacteria. Legionella bacteria were detected in 22 of 177 garden soil samples (12%) by amoebal coculture. Of these 22 Legionella-positive soil samples, seven contained Legionella pneumophila. Several other species were found, including the pathogenic Legionella longbeachae (4 gardens) and Legionella sainthelensi (9 gardens). The L. pneumophila isolates comprised 15 different sequence types (STs), and eight of these STs were previously isolated from patients according to the European Working Group for Legionella Infections (EWGLI) database. Six gardens that were found to be positive for L. pneumophila were resampled after several months, and in three gardens, L. pneumophila was again isolated. One of these gardens was resampled four times throughout the year and was found to be positive for L. pneumophila on all occasions. IMPORTANCE Tracking the source of infection for sporadic cases of Legionnaires' disease (LD) has proven to be hard. L. pneumophila ST47, the sequence type that is most frequently isolated from LD patients in the Netherlands, is rarely found in potential environmental sources. As L. pneumophila ST47 was previously isolated from a garden soil sample during an outbreak investigation, garden soils were investigated as reservoirs and potential sources of pathogenic Legionella bacteria. The detection of viable, clinically relevant Legionella strains indicates that garden soil is a potential source of Legionella bacteria, and future research should assess the public health implication of the presence of L. pneumophila in garden soil.

Legionnaires' Disease

“…Legionella bacteria have also been isolated in soil [15] . L. longbeachae is found in soil and is the only species transmitted to humans through dust or garden work but has not been shown to transmit to people through contaminated water [16] .…”

“…is another important route of transmission. L. longbeachae is believed to have a different transmission route; risk is increased by gardening and any other exposure to soil and soil products [15,16] .…”

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].…”

“…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]. [7].…”

Knowledge to Predict Pathogens: Legionella pneumophila Lifecycle Critical Review Part I Uptake into Host Cells

“…describes a gram-negative bacillus bacterium. The genus is widespread in nature, common to fresh surface water, thermal water, and drinking water environments and has been found regularly in soil samples [37][38][39]. L. pneumophila thrive in temperatures 20-50 • C with little to no growth over 50 • C, but have been isolated from hot water with temperatures as high as 66 • C [40,41].…”