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

Abstract

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/m²) and its electrons donor character have weakened (51.9–7.4 mJ/m²). However, glass gradually regains its natural surface properties (ΔG_iwi: −10.3, 0.80, 18.0 mJ/m², γ⁻: 14, 27.4, 48.3 mJ/m²). In short, the findings suggested that the reinstallation of bacterial adherents could be an energetic phenomenon related to the energetic properties of the surfaces.