Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Microbiology, floating biofilms, Legionella pneumophila, Acanthamoeba castellanii, Intracellular replication, QUANTIFICATION, INTERFACE, Aeromonas hydrophila, Analysis of Variance, Animals, Biofilms, Escherichia coli, Flavobacterium, In Situ Hybridization, Fluorescence, Microscopy, Confocal, Polymerase Chain Reaction, Pseudomonas aeruginosa, Time Factors, 0605 Microbiology, 1108 Medical Microbiology, 3107 Microbiology

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).