Loratadine inhibits the virulence and biofilm formation of Staphylococcus aureus

This study aimed to explore loratadine against the virulence and biofilm formation of Staphylococcus aureus. Biofilm biomasses were detected by crystal violet staining. The adherent cells in the mature biofilms were counted by CFU numbers and observed by confocal laser scanning microscope (CLSM). The pigments and hemolytic activities of Staphylococcus aureus which treated by loratadine were determined. The survival rate of C57/BL6J mice (pulmonary infection of S. aureus USA300 by nasal drip) which treated by loratadine was compared to the untreated mice. The RNA levels of S. aureus USA300 or SA113 genes treated by loratadine for 4 h were detected by RNA sequencing (RNA-seq), and verified by RT-qPCR. The S. aureus USA300 or SA113 strains were serially cultured under the high concentrations of loratadine, the gene mutations were determined by whole genome sequencing.