Dispersing and Sonoporating Biofilm-Associated Bacteria with Sonobactericide

Abstract

Bacteria encased in a biofilm poses significant challenges to successful treatment, since both the immune system and antibiotics are ineffective. Sonobactericide, which uses ultrasound and microbubbles, is a potential new strategy for increasing antimicrobial effectiveness or directly killing bacteria. Several studies suggest that sonobactericide can lead to bacterial dispersion or sonoporation (i.e., cell membrane permeabilization); however, real-time observations distinguishing individual bacteria during and directly after insonification are missing. Therefore, in this study, we investigated, in real-time and at high-resolution, the effects of ultrasound-induced microbubble oscillation on Staphylococcus aureus biofilms, without or with an antibiotic (oxacillin, 1 μg/mL). Biofilms were exposed to ultrasound (2 MHz, 100–400 kPa, 100–1000 cycles, every second for 30 s) during time-lapse confocal microscopy recordings of 10 min. Bacterial responses were quantified using post hoc image analysis with particle counting. Bacterial dispersion was observed as the dominant effect over sonoporation, resulting from oscillating microbubbles. Increasing pressure and cycles both led to significantly more dispersion, with the highest pressure leading to the most biofilm removal (up to 83.7%). Antibiotic presence led to more variable treatment responses, yet did not significantly impact the therapeutic efficacy of sonobactericide, suggesting synergism is not an immediate effect. These findings elucidate the direct effects induced by sonobactericide to best utilize its potential as a biofilm treatment strategy.

Infective Endocarditis during Pregnancy—Keep It Safe and Simple!

“…Sonobactericide non-invasively removes IE biofilm using ultrasound-activated lipid-coated microbubbles [ 169 , 170 ]. Recent in vitro clinical studies have demonstrated the efficacy of microbubbles against IE-associated biofilm caused by Staphylococcus aureus by 84% degradation [ 171 ]. In a similar study, Kouijzer et al [ 172 ] demonstrated that vancomycin-decorated microbubbles are able to bind to the cell walls of gram-positive bacteria.…”

Native valve, prosthetic valve, and cardiac device-related infective endocarditis: A review and update on current innovative diagnostic and therapeutic strategies

“…Another potential theranostic avenue for IE, called sonobactericide ( Lattwein et al, 2020 ), is focused on the removal of IE biofilms, non-invasively, using ultrasound-activated lipid-coated microbubbles (1–10 µm in diameter), clinically approved as ultrasound contrast agents. Non-targeted microbubbles exposed to focused and unfocused ultrasound have been shown to be effective against in vitro biofilms produced from clinical IE S. aureus isolates ( Lattwein et al, 2022 ). Ultrasound-induced microbubble displacement resulted in up to 84% biofilm degradation ( Lattwein et al, 2022 ), whereas the infected clot in vitro IE model mentioned previously in section 6.5 required the addition of thrombolytics to sonobactericide with an efficacy up to 97% ( Lattwein et al, 2018 ).…”

“…Non-targeted microbubbles exposed to focused and unfocused ultrasound have been shown to be effective against in vitro biofilms produced from clinical IE S. aureus isolates ( Lattwein et al, 2022 ). Ultrasound-induced microbubble displacement resulted in up to 84% biofilm degradation ( Lattwein et al, 2022 ), whereas the infected clot in vitro IE model mentioned previously in section 6.5 required the addition of thrombolytics to sonobactericide with an efficacy up to 97% ( Lattwein et al, 2018 ). Thrombolytics currently remain contraindicated for IE, however support exists for its use as a therapeutic agent ( Lerche et al, 2021 ).…”

Dependence of sonoporation efficiency on microbubble size: An in vitro monodisperse microbubble study

“…Besides the ultrasound frequency and pressure, the driving pulse length is also a control parameter in sonoporation therapy. A wide range of pulse lengths have been employed to induce sonoporation, i.e., from a single pulse of a few acoustic cycles [11,20,37] to many repetitions of pulses containing thousands of cycles [38][39][40][41][42]. In in vitro sonoporation experiments on cell monolayer substrates, microbubbles driven by long ultrasound pulses will cluster due to the acoustic secondary radiation force [43].…”