Objective:To investigate the therapeutic efficacy and disruptive effects of Meropenem（MEM）-loaded microbubbles（MBs）combined with ultrasound targeted microbubble destruction（UTMD）technology on Escherichia coli and its biofilm.Methods:MEM-MBs were prepared using the thin-film hydration method，and their characterization was assessed using a Zeta potential analyzer，with morphological observations conducted under an optical microscope. An in vitro biofilm model of periprosthetic joint infection（PJI）caused by Escherichia coli was constructed，and the morphology of the biofilm and the distribution of MEM-MBs in the bacterial biofilm were observed under a laser confocal microscope after staining the biofilm with SYTO59 staining and DIL staining for Microbubbles. The biofilm morphology and the distribution of MEM-MBs in bacterial biofilm were observed under laser confocal microscope. The biofilms were randomly divided into 5 groups using a random number table：control，Meropenem（MEM），MEM-MBs，UTMD，and MEM-MBs+UTMD，with 12 samples per group. After applying the respective interventions，scanning electron microscopy（SEM）and laser scanning confocal microscopy（LSCM）were employed to observe the effects on the morphology and structure of Escherichia coli and its biofilm. Crystal violet staining was utilized to determine and compare the biofilm density among groups using a microplate reader. LSCM was also used to observe the biofilm thickness，while both LSCM and spread plate counting were employed to assess bacterial viability differences across groups.Results:①MEM-MBs meeting the experimental requirements were successfully constructed.②A dense Escherichia coli biofilm visible under both the naked eye and LSCM was established，with a thickness of（10.61 ± 0.17）μm and a proportion of dead bacteria within the biofilm of（16.8 ± 0.8）%.③MEM-MBs were observed to penetrate into all layers of the biofilm using LSCM.④The results of crystal violet staining showed a decreasing trend in the biofilm density of the control group，the MEM group，the MEM-MBs group，the UTMD group，and the MEM-MBs+UTMD group. There was no significant difference between the MEM group and the MEM-MBs group（ P＞0.05），while there was a significant difference in biofilm density between the other groups，as revealed by pairwise comparison（all P＜0.05）.⑤UTMD technique and MEM-MBs+UTMD could significantly disrupt the biofilm of Escherichia coli. LSCM results showed that，compared to the control group，the thickness of the biofilm was reduced in all other groups，with only the UTMD group and the MEM-MBs+UTMD group showing an increase in porosity（both P＜0.05）. In comparison with the MEM group and the MEM-MBs group，the UTMD group showed an increase in porosity，while the MEM-MBs+UTMD group had a decrease in biofilm thickness and an increase in porosity（both P＜0.05）. Additionally，compared to the UTMD group，the MEM-MBs+UTMD group had a decrease in biofilm thickness and an increase in porosity（both P＜0.05），based on laser confocal microscopy results.⑥The results of the plate counting and LSCM showed that，compared with the control group，clump counts decreased，and the proportion of dead cells increased in the MEM group，the MEM-MBs group，and the MEM-MBs+UTMD group（all P＜0.05）. Compared with MEM group and MEM-MBs group，the clump counts of UTMD group increased，the proportion of dead cells decreased（all P＜0.05）；the clump counts of MEM-MBs+UTMD group decreased，and the proportion of dead cells increased（all P＜0.05）.Compared with UTMD group（all P＜0.05），the clump counts of MEM-MBs+UTMD group decreased，while the proportion of dead cells increased（all P＜0.05）.⑦The results of scanning electron microscopy revealed that the network structure of Escherichia coli was completely destroyed in the MEM-MBs+UTMD group. Conclusions:UTMD technology combined with MEM-MBs exerts a significant disruptive effect on the morphology and structure of Escherichia coli biofilm and significantly enhances bactericidal efficacy.

Objective:To investigate the therapeutic efficacy and disruptive effects of Meropenem（MEM）-loaded microbubbles（MBs）combined with ultrasound targeted microbubble destruction（UTMD）technology on Escherichia coli and its biofilm.Methods:MEM-MBs were prepared using the thin-film hydration method，and their characterization was assessed using a Zeta potential analyzer，with morphological observations conducted under an optical microscope. An in vitro biofilm model of periprosthetic joint infection（PJI）caused by Escherichia coli was constructed，and the morphology of the biofilm and the distribution of MEM-MBs in the bacterial biofilm were observed under a laser confocal microscope after staining the biofilm with SYTO59 staining and DIL staining for Microbubbles. The biofilm morphology and the distribution of MEM-MBs in bacterial biofilm were observed under laser confocal microscope. The biofilms were randomly divided into 5 groups using a random number table：control，Meropenem（MEM），MEM-MBs，UTMD，and MEM-MBs+UTMD，with 12 samples per group. After applying the respective interventions，scanning electron microscopy（SEM）and laser scanning confocal microscopy（LSCM）were employed to observe the effects on the morphology and structure of Escherichia coli and its biofilm. Crystal violet staining was utilized to determine and compare the biofilm density among groups using a microplate reader. LSCM was also used to observe the biofilm thickness，while both LSCM and spread plate counting were employed to assess bacterial viability differences across groups.Results:①MEM-MBs meeting the experimental requirements were successfully constructed.②A dense Escherichia coli biofilm visible under both the naked eye and LSCM was established，with a thickness of（10.61 ± 0.17）μm and a proportion of dead bacteria within the biofilm of（16.8 ± 0.8）%.③MEM-MBs were observed to penetrate into all layers of the biofilm using LSCM.④The results of crystal violet staining showed a decreasing trend in the biofilm density of the control group，the MEM group，the MEM-MBs group，the UTMD group，and the MEM-MBs+UTMD group. There was no significant difference between the MEM group and the MEM-MBs group（ P＞0.05），while there was a significant difference in biofilm density between the other groups，as revealed by pairwise comparison（all P＜0.05）.⑤UTMD technique and MEM-MBs+UTMD could significantly disrupt the biofilm of Escherichia coli. LSCM results showed that，compared to the control group，the thickness of the biofilm was reduced in all other groups，with only the UTMD group and the MEM-MBs+UTMD group showing an increase in porosity（both P＜0.05）. In comparison with the MEM group and the MEM-MBs group，the UTMD group showed an increase in porosity，while the MEM-MBs+UTMD group had a decrease in biofilm thickness and an increase in porosity（both P＜0.05）. Additionally，compared to the UTMD group，the MEM-MBs+UTMD group had a decrease in biofilm thickness and an increase in porosity（both P＜0.05），based on laser confocal microscopy results.⑥The results of the plate counting and LSCM showed that，compared with the control group，clump counts decreased，and the proportion of dead cells increased in the MEM group，the MEM-MBs group，and the MEM-MBs+UTMD group（all P＜0.05）. Compared with MEM group and MEM-MBs group，the clump counts of UTMD group increased，the proportion of dead cells decreased（all P＜0.05）；the clump counts of MEM-MBs+UTMD group decreased，and the proportion of dead cells increased（all P＜0.05）.Compared with UTMD group（all P＜0.05），the clump counts of MEM-MBs+UTMD group decreased，while the proportion of dead cells increased（all P＜0.05）.⑦The results of scanning electron microscopy revealed that the network structure of Escherichia coli was completely destroyed in the MEM-MBs+UTMD group. Conclusions:UTMD technology combined with MEM-MBs exerts a significant disruptive effect on the morphology and structure of Escherichia coli biofilm and significantly enhances bactericidal efficacy.