Pine Species Provide a Niche for <i>Legionella Longbeachae</i>

Abstract

Legionella longbeachae is the commonest cause of Legionnaires' disease (LD) nationwide in New Zealand (NZ). Most cases occur in spring and summer (October-January) and are associated with the use of commercial potting mix, which usually contains pine bark. L. longbeachae is an environmental organism but its niche has not yet been defined. Bark samples were taken at chest height from trees in three stands of Pinus radiata (Monterey pine) located in the central South Island of NZ. L. longbeachae DNA was detected by qPCR in 28/400 (7%) samples and from 22/50 (44%) different trees. There was a significant difference in the proportion of positive tests by season: summer 0/50 (0%); autumn 0/50 (0%); winter1/50 (2%); spring 22/50 (44%); (p<0.001). Bark samples from non-P. radiata pine species and adjacent mixed species were then tested. More samples from pine species 22/28 (79%) than non-pine species 6/37 (16%) tested positive for L. longbeachae (p<0.001). Pine species appear to be an important ecological niche for L. longbeachae. To our knowledge this is the second human pathogen to have an arboreal niche. The use of bark from P. radiata in commercial potting mix may contribute to the incidence of LD in New Zealand.

Presence of Viable, Clinically Relevant Legionella Bacteria in Environmental Water and Soil Sources of China

“…In addition, the average number of L. longbeachae isolates per sample in the potted soils was about 6.35 times more than those in the garden soils (0.25 versus 0.034, Table 2 ). These results indicated commercial potted soils act as more crucial niches for L. longbeachae than the garden soils, which may be due to the special niche-fitness of L.longbeachae with plant materials ( 45 ).…”

Legionellosis Caused by Non-Legionella pneumophila Species, with a Focus on Legionella longbeachae

“…These studies raise the possibility that composting facilities are contaminated with Legionella species from other sites [ 78 , 83 , 90 ]. Studies of bark from living pine trees in New Zealand found L. longbeachae DNA is common in spring, but very uncommon on bark from other tree species [ 91 ]. L. longbeachae could be brought into composting facilities with bark, and the load may contribute to the seasonal variation in clinical cases.…”

How safe are gloves and masks used for protection against Legionella longbeachae infection when gardening?

“…Two hundred microliters of the supernatant were used for DNA extraction using the GenElute Bacterial DNA extraction kit (Sigma-Aldrich, St Louis, MO) as per the manufacturer's instructions. The presence of L. longbeachae DNA was detected using the primer and probes designed and validated as specific for L. longbeachae (Herpers et al 2003;Yang et al 2010;Murdoch et al 2013;Chambers et al 2020). Positive and negative controls were included in each PCR run and negative PCR results were validated by PCR internal control.…”