Free-living freshwater amoebae differ in their susceptibility to the pathogenic bacteriumLegionella pneumophila

Abstract

Legionella pneumophila is known as a facultative intracellular parasite of free-living soil and freshwater amoebae, of which several species have been shown to support the growth of the pathogenic bacteria. We report for the first time the behaviour of two strains (c2c and Z503) of the amoeba Willaertia magna towards different strains of L. pneumophila serogroup 1 and compared it with Acanthamoeba castellanii and Hartmannella vermiformis, known to be L. pneumophila permissive. In contrast to the results seen with other amoebae, W. magna c2c inhibited the growth of one strain of Legionella (L. pneumophila, Paris), but not of others belonging to the same serogroup (L. pneumophila, Philadelphia and L. pneumophila, Lens). Also, the different L. pneumophila inhibited cell growth and induced cell death in A. castellanii, H. vermiformis and W. magna Z503 within 3-4 days while W. magna c2c strain remained unaffected even up to 7 days. Electron microscopy demonstrated that the formation of numerous replicative phagosomes observed within Acanthamoeba and Hartmannella is rarely seen in W. magna c2c cocultured with L. pneumophila. Moreover, the morphological differences were observed between L. pneumophila cultured either with Willaertia or other amoebae. These observations show that amoebae are not all equally permissive to L. pneumophila and highlight W. magna c2c as particularly resistant towards some strains of this bacterium.

The novel Legionella pneumophila type II secretion substrate NttC contributes to infection of amoebae Hartmannella vermiformis and Willaertia magna

“…That study also reported that strain Paris does not replicate in c2c Maky and Z503 willaertiae (Dey et al, 2009). Thus, our results when combined with the earlier study's findings indicate that W. magna strains can differ significantly in terms of permissiveness for different strains of L. pneumophila.…”

“…Indeed, aside from three studies that documented the intracellular growth of L. pneumophila in Echinamoeba exudans, Vahlkampfia jugosa and Willaertia magna (Dey et al, 2009;Fields et al, 1989;Rowbotham, 1986), very little is known about how L. pneumophila grows in its other known hosts. Hence, we incorporated L. pneumophila infection of W. magna into our analysis.…”

“…Legionella-laden amoebae or amoebal vesicles and cysts harbouring bacteria might also be part of the inoculum that precipitates lung infection (Berk et al, 1998;Brieland et al, 1997). Amoebae belonging to the genera Acanthamoeba, Echinamoeba, Hartmannella, Naegleria, Vahlkampfia and Willaertia coexist with L. pneumophila in water habitats, and at least 20 species representing these genera support L. pneumophila intracellular growth (Anand et al, 1983;Barbaree et al, 1986;Buse & Ashbolt, 2011;Cianciotto & Fields, 1992;Declerck et al, 2007;Dey et al, 2009;Fields et al, 1989;Fields, 1996;Harada et al, 2010;Harf & Monteil, 1988;Henke & Seidel, 1986;Holden et al, 1984;Hsu et al, 2011;Michel et al, 1998;Miyamoto et al, 2003;Molmeret et al, 2001;Newsome et al, 1985;Rowbotham, 1980Rowbotham, , 1986Tyndall & Domingue, 1982;Wadowsky et al, 1991).…”

Distribution of Sequence-Based Types of Legionella pneumophila Serogroup 1 Strains Isolated from Cooling Towers, Hot Springs, and Potable Water Systems in China

“…These results might be due to host amoebae, which adapt to and inhabit different environments (24,25). It has been reported that the growth of L. pneumophila in host amoebae depends on the bacterial genetic background (26,27). Hot spring isolates, which have unique STs adapted to amoebae, may be infectious to humans.…”

Distribution of Monoclonal Antibody Subgroups and Sequence-Based Types among Legionella pneumophila Serogroup 1 Isolates Derived from Cooling Tower Water, Bathwater, and Soil in Japan

“…These features might be related to the kind of host amoebae, which adapt to and inhabit various environments (20,23). It has been shown that the growth of L. pneumophila in some species of host amoebae depends on bacterial genetic background (4,8). Some isolates with particular STs adapted for amoebae that live in bathwater may be infectious to humans.…”