BIOFILMS AS MAJOR SOURCES OF LEGIONELLA SPP IN HYDROTHERMAL AREAS ANDTHEIR DISPERSION INTO STREAM WATER

Water and biofilms from two hydrothermal areas in central Portugal, an d one hydrothermal area in New Mexico, USA, were examined for Legionel la spp. In general, Legionella spp were isolated in higher numbers fro m biofilms than from water, although one biofilm with a temperature of 50-degrees-C, did not yield isolates of these organisms. In one area L. pneumophila serogroup (sg) 3 constituted the major population in th e thermal discharge by the stream and the biofilm below it; however, L . pneumophila sg 1 was predominant in the sediments of the stream bed with minor thermal springs below the main discharge and in the water d ownstream. No Legionellae were isolated from water upstream of the hyd rothermal area indicating that the thermal area was the source of the organisms in the stream water. In the other two hydrothermal areas, L. pneumophila sg 1 constituted the major population isolated, whereas L . pneumophila sg 3 was absent or isolated in low numbers. isolates of L. micdadei were also recovered from one hydrothermal area, while 'L. londoniensis' was isolated from another.