Effect of quorum sensing system on the infection of MRSA and the intervention of erythromycin on it

Objective To investigate the destructive effects of erythromycin on biofilm of MRSA and find the effect of erythromycin on QS related factors. Methods Tested the MBC of erythromycin on MRSA. Established the model of biofilm. Erythromycin was added into the medium when bacteria were inoculated for 24 h. Tested the biofilm and collected the supernatant or serum of rat at 6, 12, 24, 48, 72 h and 7 d after adding erythromycin to detect the concentration of autoinducing peptides (AIP). Results The MBC of the erythromycin on standard strains of MRSA was 256 g/L There is a decreasing tendency of biofilm in a short time after adding erythromycin or TSB and then gradually increase until to a steady state. Biofilm of experimental group ( 1. 348, 1. 236, 1. 667) were significantly less than the control group(1. 789, 1. 712, 2. 349 ,P < 0. 05 ) at 12, 24, 48 h. Adding erythromycin to the mature biofilm, there was a significant decrease of biofilm. Adding erythromycin within 3 hours after inoculating bacteria, there was no bacterial growth or biofilm formation. The development trend of AIP was similar with biofilm and AIP happened earlier than biofilm. With the intervention of erythromycin, AIP of experimental group (0.891 5, 0.853 9, 0.792 4) were significantly less than the control group ( 1.023 7, 1.061 6, 1. 034 7, P < 0. 05 ) at 6, 24, 48 h. Conclusion Adding erythromycin timely before biofilm formation, then bacteria were killed effectively. Erythromycin was able to destroy biofilm. Biofilm was inhibited by AIP obviously. To some extent, erythromycin can inhibit the synthesis or secretion of ATP.