Impact of High-Intensity Ultrasound on Strength of Surgical Mesh When Treating Biofilm Infections

Abstract

The use of cavitation-based ultrasound histotripsy to treat infections on surgical mesh has shown great potential. However, any impact of the therapy on the mesh must be assessed before the therapy can be applied in the clinic. The goal of this study was to determine if the cavitation-based therapy would reduce the strength of the mesh thus compromising the functionality of the mesh. First, Staphylococcus aureus biofilms were grown on the surgical mesh samples and exposed to high-intensity ultrasound pulses. For each exposure, the effectiveness of the therapy was confirmed by counting the number of colony forming units (CFUs) on the mesh. Most of the exposed meshes had no CFUs with an average reduction of 5.4-log₁₀ relative to the sham exposures. To quantify the impact of the exposure on mesh strength, the force required to tear the mesh and the maximum mesh expansion before damage were quantified for control, sham, and exposed mesh samples. There was no statistical difference between the exposed and sham/control mesh samples in terms of ultimate tensile strength and corresponding mesh expansion. The only statistical difference was with respect to mesh orientation relative to the applied load. The tensile strength increased by 1.36 N while the expansion was reduced by 1.33 mm between different mesh orientations.

Fig. 1.

The set-up utilized for the experiments when exposing the mesh samples to the high-intensity tone bursts.

Fig. 2.

Validation of combined measurement/modeling approach by com-paring modeled waveforms with waveforms at the focus measured by a hydrophone at low transducer excitation.

Fig. 3.

Modelled waveform for high-intensity therapy pulse based on measurements made in the pre-focal plane.

Fig. 4.

Mesh samples in clamps of the force test system both before and after the force has been applied.

Fig. 5.

The two different mesh orientations tested in the study.

Fig. 6.

Count of CFUs surviving on the mesh sample for both the exposed and sham treatments. The error bars correspond to one standard deviation. The numbers on each bar correspond to the number of repetitions for which CFUs were found on the mesh.

Fig. 7.

Ultimate tensile force on mesh for both mesh orientations for the control, sham, and exposed mesh samples. The error bars correspond to one standard deviation.

Fig. 8.

Clamp separation corresponding to ultimate tensile force on mesh for both mesh orientations for the control, sham, and exposed mesh samples. The error bars correspond to one standard deviation.