Discovering New Pathogens: Amoebae as Tools to Isolate Amoeba-resisting Microorganisms from Environmental Samples
Julia Lienard and Gilbert Greub
from: Environmental Microbiology: Current Technology and Water Applications (Edited by: Keya Sen and Nicholas J. Ashbolt). Caister Academic Press, U.K. (2011)
Obligate intracellular microorganisms are unculturable by classic axenic culture methods. As a result they have largely been overlooked, despite many being significant human and animal pathogens. Resistance of amoeba-resisting microorganisms (ARM) to amoebal destruction may predict ability to also resist mammalian macrophages, which are somehow similar to amoebae and represent one of the first cellular immune defenses in mammals. Thus, general approaches are described for the growth of strict intracellular microorganisms, using amoebae as hosts in a cell culture system. Such an approach has been shown to be advantageous, since amoebal co-culture will selectively grow microorganisms that resist these professional phagocytes. An alternative approach for the isolation of novel ARM is also described, which requires the isolation of new amoebal strains by amoebal enrichment on a suitable prey (such as Escherichia coli), and then to search for intra-amoebal microorganisms within the isolated amoebae. Once new potentially pathogenic ARM has been isolated, one should then further assess the potential infectivity of these intracellular microorganisms. The application of macrophages, as an in vitro model to test microbial virulence is also described read more ...