Replication of Legionella pneumophila in Floating Biofilms

Abstract

Biofilms are a major source of human pathogenic Legionella pneumophila in aquatic systems. In this study, we investigated the capacity of L. pneumophila to colonize floating biofilms and the impact of Acanthamoeba castellanii on the replication of biofilm-associated Legionella. Biofilms were grown in Petri dishes and consisted of Aeromonas hydrophila, Escherichia coli, Flavobacterium breve, and Pseudomonas aeruginosa. Six hours following inoculation, Legionella were detected in floating biofilms in mean concentrations of 1.4 x 10(4) cells/cm(2 )(real-time polymerase chain reaction) and 8.3 x 10(2) CFU/cm(2 )(culture). Two-way analysis of variance tests and fluorescent in situ hybridization clearly proved that increased biofilm-associated L. pneumophila concentrations were the result of intracellular replication in A. castellanii. Forty-eight hours after the introduction of A. castellanii in the Petri dishes, 90 +/- 0.8% of the amoebae (infection rate) were completely filled with highly metabolic active L. pneumophila (mean infection intensity).

Lcl of Legionella pneumophila Is an Immunogenic GAG Binding Adhesin That Promotes Interactions with Lung Epithelial Cells and Plays a Crucial Role in Biofilm Formation

“…To explain the high incidence of Lp1 compared to that of other Legionella species in legionellosis patients, it has been hypothesized that Lp1 is more fit for survival in aquatic environments (62). One of the strategies used by Lp1 to survive in an anthropogenic aqueous environment is to form biofilms, a process that requires adhesin(s) to fulfill the initial step of attachment (21,22,67). As it was shown that GAG binding adhesins play a role in the adherence of Lp1 to epithelial cells, we hypothesized that exogenous GAGs might also specifically in- hibit biofilm formation (81).…”

Legionella species diversity and dynamics from surface reservoir to tap water: from cold adaptation to thermophily

“…Best studied are the environmental reservoirs of L. pneumophila, which has been found in natural freshwater environments such as lakes, streams and Drinking Water Supply Systems (DWSS) (Fields, 1996). In DWSS, L. pneumophila survives planktonically, grows in biofilms and infects and replicates within protozoa (Steinert et al, 2002;Molmeret et al, 2005;Declerck et al, 2007b;Steinert et al, 2007). These bacteria can survive in moist places for a long time at relatively high temperatures and in the presence of disinfectants such as chlorine (Dupuy et al, 2011).…”

Identification of Microbial Indicators and Free Living Protozoa in Natural Mineral Water Using Cultural and Molecular Methods.

“…These pathogens can benefit from symbiosis for replication, spread (amoebae are vectors of Legionella spp. and NTM), protection, virulence and resuscitation of viable non-culturable cells [8][9][10].…”

“…Under favourable conditions within FLA, which are considered as natural primary hosts, waterborne bacteria can recover their vegetative state and regain pathogenic potential [9][10]. The World Health Organization has been classified several NTM species and Legionella pneumophila as emerging pathogens transmitted by water that may cause severe pneumonia and health-care associated pathologies, including skin and soft tissues infections, mostly in immunocompromised people [11][12][13].…”