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Differential growth of Legionella pneumophila strains within a range of amoebae at various temperatures associated with in-premise plumbing
Citation:
BUSE, H. Y. AND N. ASHBOLT. Differential growth of Legionella pneumophila strains within a range of amoebae at various temperatures associated with in-premise plumbing. Letters in Applied Microbiology. Blackwell Publishing, Malden, MA, 53(2):217-224, (2011).
Impact/Purpose:
The primary objective of the biofilm Legionella study is to determine if there is any correlation between the ability of Legionella isolates to invade and replicate within amoebal hosts and their in vivo virulence utilizing a murine model of acute bacterial pneumonia (6-8 week old A/j mice). If such a correlation is demonstrated, then a second objective will be development of an assay for the rapid identification of potentially pathogenic environmental isolates of Legionella (and latter, other intracellular bacterial pathogens) via co-culturing with an “indicator” amoebal host rather than infecting mice. Subsequent research will then focus on better understanding the stability and ecology of Legionella spp. in biofilms and the effect(s) of key stressors to select for virulent biotypes.
Description:
The potential effect of in-premise plumbing temperatures (24, 32, 37 and 41 °C) on the growth of five different L. pneumophila strains within free-living amoebae (Acanthamoeba polyphaga, Hartmannella vermiformis and Naegleria fowleri) was examined. Compared to controls only fed E. coli prey, which was digested by the three amoebae strains, when L. pneumophila was used as prey, strains Lp02 and Bloomington-2 increased in growth at 30 °C, 32 °C and 37 °C while strains Philadelphia-1 and Chicago 2 did not grow at any temperature within A. polyphaga. Strains Lp02, Bloomington-2 and Dallas 1E did not proliferate in the presence of H. vermiformis nor did strain Philadelphia-1 in the presence of N. fowleri. Yet strain Bloomington-2 grew at all temperatures examined within N. fowleri while strain Lp02 proliferated at all temperatures except 41 °C. More intriguing, strain Chicago 2 only grew at 32 °C within H. vermiformis and N. fowleri suggesting a limited temperature growth range for this strain. Results from this study indicate that identifying the presence of pathogenic legionellae may require the use of multiple host amoebae and incubation temperatures, as both influenced the type of pathogenic L. pneumophila that may be cultured from water distribution systems.