Effect of alkaline pH on staphylococcal biofilm formation

Biofilms are a serious problem, cause of severe inconvenience in the biomedical, food and industrial environment. Staphylococcus aureus and S. epidermidis are important pathogenic bacteria able to form thick and resistant biofilms on various surfaces. Therefore, strategies aimed at preventing or at least interfering with the initial adhesion and subsequent biofilm formation are a considerable achievement. The aim of this study was to evaluate the effect of alkaline pH on bacterial adhesion and further biofilm formation of S. aureus and S. epidermidis strains by biofilm biomass, cell-surface hydrophobicity, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) analysis. The results demonstrated that the amount of biofilm biomass formed and the surface hydrophobicity were significantly less than what were observed at higher levels of pH. SEM and CLSM images revealed a poorly structured and very thin biofilm (2.5-3 times thinner than that of the controls). The inhibiting effect of the alkaline pH on the bacterial attachment impaired the normal development of biofilm that arrested at the microcolony stage. Alkaline formulations could be promising towards the control of bacterial colonization and therefore the reduction of the biofilm-related hazard. In the clinical setting, alkaline solutions or cleaners could be promising to prevent the bacterial colonization, by treating surfaces such as catheters or indwelling medical devices, reducing the risk of biofilm related infections.