Reversal of NaCl effect on P. aeruginosa and E. coli bacterial adherents

Sodium chloride (NaCl) has previously been proposed as a disinfectant for water networks, where it was able to detach a bacterial adherent of Pseudomonas aeruginosa within 1 h of treatment. The purpose here was to verify the effectiveness of NaCl against P. aeruginosa and E. coli bacterial adherents over time. To this end, the NaCl effects on the bacterial adherents` stability and the surface properties of glass and strains were estimated respectively by the optical microscopy and the contact angle method. The optical microscopy’ results showed a clear detachment of both bacterial adherents after 1 h of treatment. Though, a progressive re-adhesion and formation of micro-colonies took place during the following hours of treatment. The contact angle data showed that the changes in the hydrophobicity (ΔG _iwi) of P. aeruginosa and E. coli were random throughout the treatment, while their electrons donor characters (γ ⁻) were unchanged. Meanwhile, the hydrophobicity of the glass has been reversed during the first hour (40.7 to −31.7 mJ/m ²) and its electrons donor character have weakened (51.9–7.4 mJ/m ²). However, glass gradually regains its natural surface properties (ΔG _iwi: −10.3, 0.80, 18.0 mJ/m ², γ ⁻: 14, 27.4, 48.3 mJ/m ²). In short, the findings suggested that the reinstallation of bacterial adherents could be an energetic phenomenon related to the energetic properties of the surfaces.