The potential of in situ hybridization and an immunogold assay to identify Legionella associations with other microorganisms.
Based on in vitro studies, bacteria in the genus Legionella are believed to multiply within protozoa such as amoebae in aquatic environments. Current methods used for detection of Legionella species, however, are not designed to show this relationship. Thus the natural intimate association of Legionella with other microorganisms remains to be clearly documented and the extent to which protozoa might be infected with Legionella species remains undefined. In this report we describe methods based on the use of Legionella specific reagents that would prove useful in describing its associations with other microorganisms. An immunogold and in situ hybridization technique have the potential to demonstrate the natural occurrence of Legionella species in free-living amoebae. In preliminary observations, however, bacteria reactive with Legionella specific reagents were often not intimately associated with amoebae. Bacteria occurred as free single cells, as cell aggregates, in proximity to other cells and debris, and only occasionally in close proximity to amoebae. Although some Legionella species replicate within amoebae, these preliminary observations suggest the bacteria may be encountered most frequently as extracellular microorganisms, either free-floating or in association with other structures or microorganisms. The future use of these techniques will aid in the elucidation of any naturally occurring relationships between Legionella species and other microorganisms.