Free-living amoebae (FLA) are ubiquitous in various aquatic environments. Several amoebae species are pathogenic
and host other pathogens such as Legionella, but the presence of FLA and its parasites aswell as the related
infection risk are not well known. In this study, the presence of pathogenic FLA and Legionella in various water
bodies was investigated. Water samples were collected from a river, intake areas of drinking water treatment
plants, and recreational hot spring complexes in central and southern Taiwan. A total of 140 water samples
were tested for the presence of Acanthamoeba spp., Naegleria spp., Vermamoeba vermiformis, and Legionella. In
addition, phylogenetic characteristics and water quality parameters were also assessed. The pathogenic genotypes
of FLA included Acanthamoeba T4 and Naegleria australiensis, and both were abundant in the hot spring
water. In contrast, Legionella pneumophila was detected in different aquatic environments. Among the FLA
assessed, V. vermiformis was most likely to coexist with Legionella spp. The total bacteria level was associated
with the presence of FLA and Legionella especially in hot spring water. Taken together, FLA contamination in
recreational hot springs and drinkingwater source warrants more attention on potential legionellosis and amoebae
infections.