The potential of in situ hybridization and an immunogold assay to identifyLegionella 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 Legion ella with other microorganisms remains to be clearly documented and the ext ent to which protozoa might be infected with Legionella species remains und efined. In this report we describe methods based on the use of Legionella s pecific reagents that would prove useful in describing its associations wit h other microorganisms. An immunogold and in situ hybridization technique h ave the potential to demonstrate the natural occurrence of Legionella speci es in free-living amoebae. Zn preliminary observations, however, bacteria r eactive with Legionella specific reagents were often not intimately associa ted with amoebae. Bacteria occurred as free single cells, as cell aggregate s, in proximity to other cells and debris, and only occasionally in close p roximity to amoebae. Although some Legionella species replicate within amoe bae, these preliminary observations suggest the bacteria may be encountered most frequently as extracellular microorganisms, either free-floating or i n association with other structures or microorganisms. The future use of th ese techniques will aid in the elucidation of any naturally occurring relat ionships between Legionella species and other microorganisms. (C) 1999 Else vier Science B.V. All rights reserved.