Role of Staphylococcus aureus Buoyant Density in the Development of Biofilm Associated Antibiotic Resistance

Bacterial biofilms are clusters of bacterial cells that form at various interfaces, including those between air and liquid or liquid and solid. Due to their roles in enhancing wastewater treatment processes, and their unfortunate propensity to cause persistent human infections through high antibiotic resistance, understanding and managing bacterial biofilms is of paramount importance. A pivotal stage in biofilm development is the initial bacterial attachment to these interfaces. However, the determinants of bacterial cell choice in colonizing an interface first and heterogeneity in bacterial adhesion remain elusive. Recent research has unveiled variations in the buoyant density of Staphylococcus aureus cells, irrespective of their growth phase. Cells with a low cell buoyant density, characterized by fewer cell contents, exhibited greater resistance to antibiotic treatments (100 g/mL vancomycin) and favored biofilm formation at air-liquid interfaces. In contrast, cells with higher buoyant cell density, which have richer cell contents, were more vulnerable to antibiotics and predominantly formed biofilms on liquid-solid interfaces when contained upright. In essence, S. aureus cells with higher buoyant cell density are more inclined to adhere to upright substrates.