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Objective: Legionella is a waterborne pathogen that causes a severe form of pneumonia called Legionnaires' diseases, which is normally acquired by inhalation of aerosols containing Legionella origi...

The aim of this study was to evaluate the effect of chemical compounds found in different water types on the physico-chemical properties of bacteria and the adhesion of two strains (Pseudomonas aeruginosa and Escherichia coli) to glass, PVC and stainless steel. P. aeruginosa and E. coli were exposed to two sterile water types (distilled water and tap water) for 3 h. Contact angle measurements were used to assess the surface properties of both strains and coupons of different materials. The hydrophobicity and the electron donor properties of the bacterial strains seems to increase when exposed to sterile tap water compared to distilled water, while the electron acceptor property is largely unchanged. The adhesion tests were carried out in a water circuit creating turbulence. The number of adhered cells was determined after their detachment from the coupons using an ultrasonic bath for 2 min. The findings showed that the type of water affects the adhesion of both strains, which is stronger in tap water than distilled water. A correlation test to determine the surface property that governs adhesion in these conditions, suggested that the adhesion is mainly governed by hydrophobicity.

Background and Objectives: Legionnaires’ disease continues to be a public health concern. Colonized water distribution systems are often implicated in Legionella transmission, despite the use of various disinfection strategies, the bacterium is capable to persist and survive in water systems. The aim of this study was to investigate the persistence of Legionella pneumophila to sodium chloride over time at different temperatures and analysing the role of biofilms in the survival of this bacteria. Materials and Methods: L. pneumophila serogroup 1 and L. pneumophila serogroup 2-15 were used to study the effect of sodium chloride on planktonic and sessile cells. The tested concentrations were: 0.5%, 1%, 2%, 3%, 4%, 6% and 8% (W/V) NaCl. Biofilms were grown on 24-well microplates. Results: At 20°C, L. pneumophila planktonic cells were able to survive in sodium chloride concentrations up to 2%. How- ever, at 37°C, a sodium chloride concentration over 1.5%, reduced systematically the numbers of bacterial cells. Biofilms were grown for 20 days in the absence and presence of sodium chloride. The results show that bacterial strains were able to survive and regrow after the sodium chloride shock (2-3%). Moreover, it seems that this effect is less expressed with the age of the biofilm; old biofilms were more persistent than the young ones. Conclusion: Results from this study demonstrate that the sodium chloride disinfection strategy was effective on Legionella pneumophila planktonic cells but not on biofilms, which demonstrate the role of biofilms in the persistence and recoloniza- tion of L. pneumophila in water distribution systems.

We aimed to investigate the adhesion of Legionella pneumophila serogroup1 and L. pneumophila serogroup2-15 on glass, galvanized steel, stainless steel, copper, Polyvinyl chloride(PVC), Cross-linked polyethylene(PEX-c) and Polypropylene Random Copolymer(PPR). The surface physicochemical properties of both bacterial cells and materials were estimated through contact angle measurements. The roughness and surface topography of the materials were evaluated by Atomic Force Microscopy. The two L. pneumophila serogroups and plumbing materials showed a hydrophobic character, while glass surface was hydrophilic. All strains were adhered to all materials with the exception of copper. The result showed that the adhesion of both L. pneumophila sg1 and sg2-15 was systematically expressed with high intensity on galvanized steel followed by PVC, PEX-c, PPR, stainless steel and the low intensity on glass. The extent of adhesion is in correlation with the surface roughness and acid-bases interactions, while hydrophobicity seems to have no effect in adhesion intensity.

The purpose of our study was to investigate the biofilm formation by Legionella pneumophila serogroup1 and serogroup2-15 on plumbing materials mostly used in building water systems in Morocco. The ...