Comparative Study on the Impact of Growth Conditions on the Physiology and the Virulence of Pseudomonas aeruginosa Biofilm and Planktonic Cells.

The aim of the present work was to study and compare the effect of growth temperature (20, 30, and 37°C) and surface type (stainless steel and polycarbonate) on the production of virulence factors, such as proteases and siderophores, and the risk of surface contamination associated with Pseudomonas aeruginosa biofilm and planktonic cells. The increase of growth temperature from 20 to 37°C increased (approximately twofold) the electronegative charge and the hydrophobicity of the P. aeruginosa biofilm cell surface. P. aeruginosa biofilm cell adhesion to stainless steel and polycarbonate was 5- and 1.5-fold higher than their planktonic counterparts at 20 and 30°C, respectively. The increase of growth temperature from 20 to 37°C increased the production of proteases (twofold) and siderophores (twofold) and the cytotoxicity (up to 30-fold) against the HeLa cell line in the supernatants of P. aeruginosa planktonic and biofilm cultures. This study also highlighted that biofilm and planktonic P. aeruginosa cells exhibited distinct physiological properties with respect to the production of virulence factors and the cytotoxicity against the Hela cell line. Therefore, effective disinfection procedures should be adapted to inactivate bacteria detached from biofilms.

Actively detached Pseudomonas aeruginosa biofilm cell susceptibility to benzalkonium chloride and associated resistance mechanism.

The present work aimed at studying physiological properties of Pseudomonas aeruginosa cells actively detached from biofilm formed on stainless steel and comparing them with their planktonic counterparts as a function of growth temperature (20 °C and 37 °C). The susceptibility of P. aeruginosa cells to benzalkonium chloride (BAC) was studied. Furthermore, the effect of BAC on the cell membrane integrity and the role of the cell membrane fluidity in the cell-scale-resistance mechanism were investigated. Our results showed that actively detached biofilm cells were more susceptible to BAC treatment than planktonic ones. A greater leakage of intracellular potassium after BAC addition was observed in actively detached biofilm cells, which reflects their membrane vulnerability. The rise of the growth temperature from 20 to 37 °C increased the membrane rigidity of planktonic cells comparatively to their actively detached biofilm ones. Under experimental conditions developed in this work, our data highlighted that actively biofilm-detached and planktonic P. aeruginosa cells have distinguishable phenotypes.

Impact of growth temperature on the adhesion of colistin-resistant Escherichia coli strains isolated from pigs to food-contact-surfaces.

This study investigated the effect of the growth temperature (20 and 37 °C) of Escherichia coli strains isolated from pigs on their adhesion to stainless steel and polycarbonate. This study also evaluated the ability of the DLVO and XDLVO mathematical models to predict this adhesion. The rise of growth temperature from 20 to 37 °C significantly influenced the adhesion of studied E. coli strains. The data also underlined that the mathematical prediction did not fully match with the experimental bacterial adhesion to surfaces. Furthermore, results showed that the colistin-resistant and sensitive E. coli strains adhesion depends on the type of abiotic surface. Based on these results, the mathematical models are limited in the prediction of the bacterial adhesion to abiotic surfaces. The surface roughness is a major parameter of the bacterial adhesion and should be included in the future mathematical models predicting the bacterial adhesion.

Correction to: Effect of incubation duration, growth temperature, and abiotic surface type on cell surface properties, adhesion and pathogenicity of biofilm-detached Staphylococcus aureus cells.

Following publication of the original article (Khelissa et al. 2017), the authors reported that the legend for Fig. 3 contained an error. Instead of "Adhesion of planktonic and biofilm-detached Staphylococcus aureus cells on stainless steel and polycarbonate. Cell cultures were grown at 20, 30 and 37 °C, during 24 h (white square) and 48 h (white square). Planktonic cells adhesion on stainless steel (a) and polycarbonate (b). Adhesion of stainless steel-biofilm-detached-cells on stainless steel 24 (c) and polycarbonate-biofilm-detached-cells on polycarbonate (d)", the legend should read "Adhesion of planktonic and biofilm-detached Staphylococcus aureus cells on stainless steel and polycarbonate. Cell cultures were grown at 20, 30 and 37 °C, during 24 h (black square) and 48 h (white square). Planktonic cells adhesion on stainless steel (a) and polycarbonate (b). Adhesion of stainless steel-biofilm-detached-cells on stainless steel 24

Effect of incubation duration, growth temperature, and abiotic surface type on cell surface properties, adhesion and pathogenicity of biofilm-detached Staphylococcus aureus cells.

The goal of this study was to investigate the effect of growth conditions such as the temperature (20, 30 and 37 °C), incubation duration (24 and 48 h) and surface type (stainless steel and polycarbonate) on the cell surface physicochemical properties and adhesion to abiotic surfaces of biofilm-detached and planktonic Staphylococcus aureus cells. This study tested also the hypothesis that S. aureus planktonic cells exhibit distinct pathogenic properties compared with their sessile counterparts. The results showed that the changes of the growth conditions promoted changes in the zeta potential, hydrophobicity, electron donor/acceptor character of the studied cell populations. Biofilm-detached cells showed a greater adhesion to stainless steel and polycarbonate compared with planktonic cells. Compared with planktonic cells, sessile ones showed higher cytotoxic effect against HeLa cells, DNase activity, and siderophore levels. The higher cytotoxic effect and production of DNase and siderophore increased with the increase of temperature and duration of incubations. Based on the obtained data, the S. aureus biofilm-detached cells were found to be distinct in many physiological properties compared with their planktonic counterparts.