Abstract
In this research we compared the proportion of samples taken at different stages in the manufacturing process of potting soils that were qPCR positive for Legionella longbeachae. This included samples of composted feed stock, mixing sites and bagged products. Feedstock, manufacturing sites, and final retail products at three locations across the North and South Islands of New Zealand were tested for L. longbeachae DNA by qPCR. Positive tests were found on samples of composted pine bark 14/360 (3.9%), pine sawdust 5/185 (2.7%) and pre-bagged or bagged potting soils 9/200 (4.5%). All samples from peat (n = 20), green waste (n = 100), and mixing areas (n = 73) were negative. Samples that contained pine bark or pine sawdust were more likely to be qPCR positive (28/818, 3.4%) than other samples (0/355, 0%; P<0.001). L. longbeachae probably reaches the manufacturing sites from fresh pine bark and persists through the composting and manufacturing process, leading to a wide distribution following the purchase.