The influence of ultrasound on the fluoroquinolones antibacterial activity

Sono-Triggered Biomimetically Nanoantibiotics Mediate Precise Sequential Therapy of MRSA-Induced Lung Infection

Bacterial-induced lower respiratory tract infections are a growing global health concern, exacerbated by the inefficacy of conventional antibiotics and delivery methods to effectively target the lower respiratory tract, leading to suboptimal therapeutic outcomes. To address this challenge, this work engineers PBP2a antibody-presenting membrane nanovesicles (AMVs) specifically designed to target the penicillin-binding protein variant on the surface of methicillin-resistant Staphylococcus aureus (MRSA). Concurrently, this work develops pure ciprofloxacin nanoparticles (NanoCip) that, for the first time, exhibits exceptional self-generated sonodynamic properties, attributed to hydrogen-bond-driven self-assembly, while maintaining their inherent pharmacological efficacy. These NanoCip particles are integrated with AMVs to create a novel biomimetic nanomedicine, AMV@NanoCip. This formulation demonstrated remarkable MRSA-targeting affinity in both in vitro and in vivo models, significantly enhancing antibacterial activity. Upon ultrasound stimulation, AMV@NanoCip achieves over 99.99% sterilization of MRSA in vitro, with a reduction exceeding 5.14 Log CFU. Prokaryotic transcriptomic analysis further elucidates the synergistic mechanisms by which AMV@NanoCip, coupled with ultrasound, disrupts the MRSA exoskeleton. In a MRSA-induced pneumonia animal model, AMV@NanoCip+US results in a substantial bacterial load reduction in the lungs (99.99%, 4.02 Log CFU). This sequential treatment strategy (adhesion-membrane disruption-synergistic therapy) offers significant promise as an innovative therapeutic approach for combating bacterial infections.

Comparative study of synergistic antibacterial activity of ciprofloxacin-capped gold nanoparticles under different ultrasound frequency

Sonodynamic antimicrobial chemotherapy (SACT), as a novel anti-infective program, has received tremendous attention due to its good tissue penetration depth and low invasion. Ultrasound (US) frequency was one of the important parameters for SACT. To investigate the influence of different US frequencies on sonodynamic antimicrobial activity of ciprofloxacin-capped gold nanoparticles (CIP:GNPs). C. albicans and E. coli were chosen as the action objects. The bacterial survival rate was used in the assessment index and measured by plate colony-counting methods. The reactive oxygen species (ROS) produced under US irradiation were detected by ROS fluorescence probe and used to analyze the sonodynamic antibacterial mechanism of CIP:GNPs following different US frequencies. High-frequency US combined with CIP:GNPs had a good synergistic antimicrobial impact on C. albicans, while medium-frequency US showed a strong effect on E. coli. Moreover, the mechanism research experiment proved that intracellular ROS levels were closely related to changes in US frequency, and significantly affected the synergistic activity of CIP:GNPs. The injury of E. coli appearance showed more sensitivity to the change of US frequency than that of C. albicans, but its action laws were relatively complicated and needed to be further studied.

Bibliometric and visualized analysis of ultrasound combined with microbubble therapy technology from 2009 to 2023

Background

In recent years, with the rapid advancement of fundamental ultrasonography research, the application of ultrasound in disease treatment has progressively increased. An increasing body of research indicates that microbubbles serve not only as contrast agents but also in conjunction with ultrasound, enhancing cavitation effects and facilitating targeted drug delivery, thereby augmenting therapeutic efficacy. The objective of this study is to explore the current status and prevailing research trends in this field from 2009 to 2023 through bibliometric analysis and to forecast future developmental trajectories.

Methods

We selected the Science Citation Index Expanded (SCI-Expanded) from the Web of Science Core Collection (WOSCC) as our primary data source. On 19 January 2024, we conducted a comprehensive search encompassing all articles and reviews published between 2009 and 2023 and utilized the bibliometric online analysis platform, CiteSpace and VOSviewer software to analyze countries/regions, institutions, authors, keywords, and references, used Microsoft Excel 2021 to visualize the trends of the number of articles published by year.

Results

Between 1 January 2009, and 31 December 2023, 3,326 publications on ultrasound combined with microbubble therapy technology were included. There were a total of 2,846 articles (85.6%) and 480 reviews (14.4%) from 13,062 scholars in 68 countries/regions published in 782 journals. China and the United States emerged as the primary contributors in this domain. In terms of publication output and global institutional collaboration, the University of Toronto in Canada has made the most significant contribution to this field. Professor Kullervo Hynynen has achieved remarkable accomplishments in this area. Ultrasound in Medicine and Biology is at the core of the publishing of research on ultrasound combined with microbubble therapy technology. Keywords such as "sonodynamic therapy," "oxygen," "loaded microbubbles" and "Alzheimer's disease" indicate emerging trends in the field and hold the potential to evolve into significant areas of future investigation.

Conclusion

This study provides a summary of the key contributions of ultrasound combined with microbubble therapy to the field's development over the past 15 years and delves into the historical underpinnings and contemporary trends of ultrasound combined with microbubble therapy technology, providing valuable guidance for researchers.

Nano-Emulsified Perfluorooctyl Bromide Can Infiltrate Gram-Negative Bacteria and Sensitize Them to Ultrasound

Gram-negative (G-) bacterial infections remain one of the most urgent global health threats, because the distinctive envelope structure hinders the penetration of therapeutics. Here, we showed that a perfluorooctyl bromide nanoemulsion (PFOB NE) uniquely interacts with G- bacteria. After cell envelope attachment, the PFOB can infiltrate the cell and was diffused throughout. In this process, it impaired the membranes by disintegrating phospholipid molecules, enhancing the consequent ultrasonic cavitation to break the envelope. We identified through ultrasound that the NE had remarkable bactericidal effects against various antibiotic-resistant pathogens. Using in situ sterilization, this approach accelerated the recovery of bacteria-infected murine skin wounds. Thus, combining PFOB and ultrasound might be an alternative tool for conquering the growing threat of G- pathogens.

Synthesis and Sonodynamic Antibacterial Activity Evaluation of Three Novel Fluoroquinolone Compounds

OBJECTIVE

Three ciprofloxacin derivatives (CPDs) were synthesized. Also, their sonodynamic antibacterial activities and possible mechanism under ultrasound (US) irradiation were preliminarily investigated.

METHODS

Staphylococcus aureus and Escherichia coli were selected as the research objects. The sonodynamic antibacterial effects of three CPDs and their structure-effective relationship were explored by the inhibition rate. The reactive oxygen species (ROS) produced under US irradiation were detected by oxidative extraction spectrophotometry and used to analyze the sonodynamic antibacterial mechanism of three CPDs.

RESULTS

Research indicated that three CPDs, named compound 1 (C1), compound 2 (C2) and compound 3 (C3), separately all had strong sonodynamic antibacterial activities. In addition, C3 had the strongest effect relative to the other CPDs. The study also found that CPDs' concentration, US irradiation time, US solution temperature and US medium could disturb their sonodynamic antimicrobial effects. Moreover, ¹O₂ and ·OH were the main types of ROS produced by C1 and C3; the ROS produced by C2 included ¹O₂, among other types.

CONCLUSION

Results showed that all three CPDs could be activated to produce ROS after US irradiation. Among them, C3 displayed the highest ROS production and the utmost activity, which may be related to the introduction of the electron-giving group at the C-3 position of the quinoline backbone.

Ultrasonic interfacial crosslinking of TiO2-based nanocomposite hydrogels through thiol-norbornene reactions for sonodynamic antibacterial treatment

Nanocomposite (NC) hydrogels used for sonodynamic therapy (SDT) face challenges such as lacking interfacial interactions between the polymers and nanomaterials as well as presenting uneven dispersion of nanomaterials in the hydrogel network, reducing their mechanical properties and treatment efficiency. Here, we demonstrate a promising approach of co-engineering nanomaterials and interfacial crosslinking to expand the materials construction and biomedical applications of NC hydrogels in SDT. In this work, mesoporous silica-coated titanium dioxide nanoparticles with thiolated surface functionalization (TiO₂@MS-SH) are utilized as crosslinkers to react with norbornene-functionalized dextran (Nor-Dex) through ultrasound-triggered thiol-norbornene reactions, forming TiO₂@MS-SH/Nor-Dex NC hydrogels. The TiO₂@MS-SH nanoparticles act not only as multivalent crosslinkers to improve the mechanical properties of hydrogels under ultrasound irradiation but also as reactive oxygen species (ROS) generators to allow the use of TiO₂@MS-SH/Nor-Dex NC hydrogels in SDT applications. Particularly, the TiO₂@MS-SH/Nor-Dex NC hydrogels present tailorable microstructures, properties, and sonodynamic killing of bacteria through the modulation of the ultrasound frequency. Taken together, a versatile TiO₂-based NC hydrogel platform prepared under ultrasonic interfacial crosslinking reactions is developed for advancing the applications in SDT.

Emerging nanosonosensitizers augment sonodynamic-mediated antimicrobial therapies

With the widespread prevalence of drug-resistant pathogens, traditional antibiotics have limited effectiveness and do not yield the desired outcomes. Recently, alternative antibacterial therapies based on ultrasound (US) have been explored to overcome the crisis of bacterial pathogens. Antimicrobial sonodynamic therapy (aSDT) offers an excellent solution that relies on US irradiation to produce reactive oxygen species (ROS) and achieve antibiotic-free mediated antimicrobial effects. In addition, aSDT possesses the advantage of superior tissue penetrability of US compared to light irradiation, demonstrating great feasibility in treating deep infections. Although existing conventional sonosensitizers can produce ROS for antimicrobial activity, some limitations, such as low penetration rate, nonspecific distribution and poor ROS production under hypoxic conditions, result in suboptimal sterilization in aSDT. Recently, emerging nanosonosensitizers have enormous advantages as high-performance agents in aSDT, which overcome the deficiencies of conventional sonosensitizers as described above. Thus, nanosonosensitizer-mediated aSDT has a bright future for the management of bacterial infections. This review classifies the current available nanosonosensitizers and provides an overview of the mechanisms, biomedical applications, recent advances and perspectives of aSDT.

Synthesis of Ciprofloxacin-capped Gold Nanoparticles Conjugates with Enhanced Sonodynamic Antimicrobial Activity in vitro

The purpose of this article is to discuss whether gold nanoparticles (GNPs) play an auxo-action on ciprofloxacin (CIP)-mediated sonodynamic antimicrobial chemotherapy (SACT) in vitro. The measuring criterion of SACT, bactericidal efficiency, was measured by plate colony-counting methods. According to research findings, the duration of ultrasound (US) exposure, solution temperature and CIP:GNPs concentration were all critical influencing factors of SACT. Furthermore, scanning electron microscopy revealed that the group of CIP:GNPs combined with US showed the most severe damaged effect on Escherichia coli and Staphylococcus aureus, resulting in the loss of their typical microbial morphology and the disclosure of contents. Therefore, the above experimental results confirmed initially that GNPs could enhance the bacteriostasis of CIP-mediated SACT. And the intracellular reactive oxygen species (ROS) detection assays proved that this acceleration might be connected to the ROS generated through the ultrasonic mechanics. In conclusion, GNPs would be regarded as a promising auxiliary material for SACT, since they are both used to be the medication carriers and sonosensitizer accelerants.

Synergistic antibacterial effects of ultrasound combined nanoparticles encapsulated with cellulase and levofloxacin on Bacillus Calmette-Guérin biofilms

Tuberculosis is a chronic infectious disease, the treatment of which is challenging due to the formation of cellulose-containing biofilms by Mycobacterium tuberculosis (MTB). Herein, a composite nanoparticle loaded with cellulase (CL) and levofloxacin (LEV) (CL@LEV-NPs) was fabricated and then combined with ultrasound (US) irradiation to promote chemotherapy and sonodynamic antimicrobial effects on Bacillus Calmette-Guérin bacteria (BCG, a mode of MTB) biofilms. The CL@LEV-NPs containing polylactic acid-glycolic acid (PLGA) as the shell and CL and LEV as the core were encapsulated via double ultrasonic emulsification. The synthesized CL@LEV-NPs were uniformly round with an average diameter of 196.2 ± 2.89 nm, and the zeta potential of -14.96 ± 5.35 mV, displaying high biosafety and sonodynamic properties. Then, BCG biofilms were treated with ultrasound and CL@LEV-NPs separately or synergistically in vivo and in vitro. We found that ultrasound significantly promoted biofilms permeability and activated CL@LEV-NPs to generate large amounts of reactive oxygen species (ROS) in biofilms. The combined treatment of CL@LEV-NPs and US exhibited excellent anti-biofilm effects, as shown by significant reduction of biofilm biomass value and viability, destruction of biofilm architecture in vitro, elimination of biofilms from subcutaneous implant, and remission of local inflammation in vivo. Our study suggested that US combined with composite drug-loaded nanoparticles would be a novel non-invasive, safe, and effective treatment modality for the elimination of biofilm-associated infections caused by MTB.

The Combination of Low-Frequency Ultrasound and Antibiotics Improves the Killing of In Vitro Staphylococcus aureus and Pseudomonas aeruginosa Biofilms

Due to an increase in underlying predisposing factors, chronic wounds have become an increasing burden on healthcare systems worldwide. Chronic infections often contain biofilm-forming bacteria, which are challenging to eradicate due to increased antibiotic tolerance; thus, new and improved therapeutic strategies are warranted. One such strategy is the combination of ultrasound and antibiotics. Therefore, this study aimed to investigate the combinatory effects of low-frequency (50 kHz) ultrasound delivered by specially designed ultrasound patches using flexible piezoelectric material, PiezoPaint™, in combination with antibiotics against biofilms with Staphylococcus aureus and Pseudomonas aeruginosa. The reduction in viable cells in S. aureus and P. aeruginosa biofilms was evaluated post-treatment with fusidic acid, clindamycin, ciprofloxacin, and colistin in combination with ultrasound treatment. Two-hour ultrasound treatment significantly increased the bactericidal effect of all four antibiotics, resulting in a 96−98% and 90−93% reduction in P. aeruginosa and S. aureus, respectively. In addition, an additive effect was observed when extending treatment to 4 h, resulting in >99% and 95−97% reduction in P. aeruginosa and S. aureus, respectively. These results contrasted the lack of effect observed when treating filter-biofilms with antibiotics alone. The combined effect of ultrasound and antibiotic treatment resulted in a synergistic effect, reducing the viability of the clinically relevant pathogens S. aureus and P. aeruginosa. The modularity of the specially designed patches intended for topical treatment holds promising applications as a supplement in chronic wound therapy. Further studies are warranted with clinically isolated strains and other clinically relevant antibiotics before proceeding to studies where safety and applicability are investigated.

Recent developments of sonodynamic therapy in antibacterial application

The rapid emergence of pathogenic bacteria poses a serious threat to global health. Notably, traditional antibiotic therapies suffer from the risk of strengthening bacterial drug resistance. Sonodynamic therapy (SDT) combining sonosensitizers and low-intensity ultrasound (US) has broadened the way towards treating drug-resistant bacteria. The allure of this therapy emerges from the capacity to focus the US energy on bacterial infection sites buried deep in tissues, locally activating the sonosensitizers to produce cytotoxic reactive oxygen species (ROS) with the ability to induce bacterial death. The past decade has witnessed the rapid development of antibacterial SDT owing to their excellent penetration, favorable biocompatibility and specific targeting ability. This review summarizes available sonosensitizers for antibacterial SDT, and digs into innovative biotechnologies to improve SDT efficiency, such as enhancing the targeting ability of sonosensitizers, image-guided assisted SDT, improvement of hypoxia and combination of SDT with other therapies. Finally, we conclude with the present challenges and provide insights into the future research of antibacterial SDT.

Excited state and reactive oxygen species against cancer and pathogens: a review on sonodynamic and sono-photodynamic therapy

Photodynamic and sonodynamic therapy are therapies having great potential in the treatment of bacterial infections and cancer. Their background is associated with photo- and sonosensitizers - substances that can be excited when exposed to light or ultrasound. These sensitizers belong to a variety of compounds groups, including porphyrins, porphyrazines, and phthalocyanines. Releasing the energy when returning to the ground state can occur in the manner of transferring it to oxygen molecules, leading to reactive oxygen species able to disrupt membranes of bacterial and cancer cells, leaving the organism's cells unaffected. In recent years, the number of reports on numerous sensitizers being effective has been constantly growing. Therefore, the development of this field may prove beneficial for dealing with cancer and microbes. This review describes the development of photodynamic and sonodynamic therapy, as well as their combination, with emphasize on sonodynamic therapy and its potential in the treatment of cancer and bacterial infections.

Enhanced antimicrobial activity through the combination of antimicrobial photodynamic therapy and low-frequency ultrasonic irradiation

The rapid increase of antibiotic resistance in pathogenic microorganisms has become one of the most severe threats to human health. Antimicrobial photodynamic therapy (aPDT), a light-based regimen, has offered a compelling nonpharmacological alternative to conventional antibiotics. The activity of aPDT is based on cytotoxic effect of reactive oxygen species (ROS), which are generated through the photosensitized reaction between photon, oxygen and photosensitizer. However, limited by the penetration of light and photosensitizers in human tissues and/or the infiltration of oxygen and photosensitizers in biofilms, the eradication of deeply located or biofilm-associated infections by aPDT remains challenging. Ultrasound irradiation bears a deeper penetration in human tissues than light and, sequentially, can promote drug delivery through cavitation effect. As such, the combination of ultrasound and aPDT represents a potent antimicrobial strategy. In this review, we summarized the recent progresses in the area of the combination therapy using ultrasound and aPDT, and discussed the potential mechanisms underlying enhanced antimicrobial effect by this combination therapy. The future research directions are also highlighted.

Progress in Alternative Strategies to Combat Antimicrobial Resistance: Focus on Antibiotics

Antibiotic resistance, and, in a broader perspective, antimicrobial resistance (AMR), continues to evolve and spread beyond all boundaries. As a result, infectious diseases have become more challenging or even impossible to treat, leading to an increase in morbidity and mortality. Despite the failure of conventional, traditional antimicrobial therapy, in the past two decades, no novel class of antibiotics has been introduced. Consequently, several novel alternative strategies to combat these (multi-) drug-resistant infectious microorganisms have been identified. The purpose of this review is to gather and consider the strategies that are being applied or proposed as potential alternatives to traditional antibiotics. These strategies include combination therapy, techniques that target the enzymes or proteins responsible for antimicrobial resistance, resistant bacteria, drug delivery systems, physicochemical methods, and unconventional techniques, including the CRISPR-Cas system. These alternative strategies may have the potential to change the treatment of multi-drug-resistant pathogens in human clinical settings.

Antibacterial Sonodynamic Therapy: Current Status and Future Perspectives

Multidrug-resistant bacteria have emerged in both community and hospital settings, partly due to the misuse of antibiotics. The inventory of viable antibiotics is rapidly declining, and efforts toward discovering newer antibiotics are not yielding the desired outcomes. Therefore, alternate antibacterial therapies based on physical mechanisms such as light and ultrasound are being explored. Sonodynamic therapy (SDT) is an emerging therapeutic approach that involves exposing target tissues to a nontoxic sensitizing chemical and low-intensity ultrasound. SDT can enable site-specific cytotoxicity by producing reactive oxygen species (ROS) in response to ultrasound, which can be harnessed for treating bacterial infections. This approach can potentially be used for both superficial and deep-seated microbial infections. The majority of the sonosensitizers reported are nonpolar, exhibiting limited bioavailability and a high clearance rate in the body. Therefore, targeted delivery agents such as nanoparticle composites, liposomes, and microbubbles are being investigated. This article reviews recent developments in antibacterial sonodynamic therapy, emphasizing biophysical and chemical mechanisms, novel delivery agents, ultrasound exposure and image guidance strategies, and the challenges in the pathway to clinical translation.

Levofloxacin-Loaded Nanosonosensitizer as a Highly Efficient Therapy for Bacillus Calmette-Guérin Infections Based on Bacteria-Specific Labeling and Sonotheranostic Strategy

Purpose

The rapid emergence of multidrug-resistant Mycobacterium tuberculosis (MTB) poses a significant challenge to the treatment of tuberculosis (TB). Sonodynamic antibacterial chemotherapy (SACT) combined with sonosensitizer-loaded nanoparticles with targeted therapeutic function is highly expected to eliminate bacteria without fear of drug resistance. This study aimed to investigate the antibacterial effect and underlying mechanism of levofloxacin-loaded nanosonosensitizer with targeted therapeutic function against Bacillus Calmette-Guérin bacteria (BCG, an MTB model).

Methods

This study developed levofloxacin-loaded PLGA-PEG (poly lactide-co-glycolide-polyethylene glycol) nanoparticles with BM2 aptamer conjugation on its surface using the crosslinking agents EDC and NHS (BM2-LVFX-NPs). The average diameter, zeta potential, morphology, drug-loading properties, and drug release efficiency of the BM2-LVFX-NPs were investigated. In addition, the targeting and toxicity of BM2-LVFX-NPs in the subcutaneous BCG infection model were evaluated. The biosafety, reactive oxygen species (ROS) production, cellular phagocytic effect, and antibacterial effect of BM2-LVFX-NPs in the presence of ultrasound stimulations (42 kHz, 0.67 W/cm², 5 min) were also systematically evaluated.

Results

BM2-LVFX-NPs not only specifically recognized BCG bacteria in vitro but also gathered accurately in the lesion tissues. Drugs loaded in BM2-LVFX-NPs with the ultrasound-responsive feature were effectively released compared to the natural state. In addition, BM2-LVFX-NPs exhibited significant SACT efficiency with higher ROS production levels than others, resulting in the effective elimination of bacteria in vitro. Meanwhile, in vivo experiments, compared with other options, BM2-LVFX-NPs also exhibited an excellent therapeutic effect in a rat model with BCG infection after exposure to ultrasound.

Conclusion

Our work demonstrated that a nanosonosensitizer formulation with LVFX could efficiently translocate therapeutic drugs into the cell and improve the bactericidal effects under ultrasound, which could be a promising strategy for targeted therapy for MTB infections with high biosafety.

Sonodynamic antimicrobial chemotherapy: An emerging alternative strategy for microbial inactivation

Sonodynamic antimicrobial chemotherapy (SACT), which relies on a combination of low-intensity ultrasound and chemotherapeutic agents termed sonosensitizers, has been explored as a promising alternative for microbial inactivation. Such treatment has superior penetration ability, high target specificity, and can overcome resistance conferred by the local microenvironment. Taken of these advantages, SACT has been endowed with an extensive application prospect in the past decade and attracted more and more attention. This review focusses on the current understanding of the mechanism of SACT, the interaction of sonodynamic action on different microbes, the factors affecting the efficacy of SACT, discusses the findings of recent works on SACT, and explores further prospects for SACT. Thus, a better understanding of sonodynamic killing facilitates the scientific community and industry personnel to establish a novel strategy to combat microbial burden.

Synergistic inactivation of bacteria based on a combination of low frequency, low-intensity ultrasound and a food grade antioxidant

This study evaluated a synergistic antimicrobial treatment using a combination of low frequency and a low-intensity ultrasound (LFU) and a food-grade antioxidant, propyl gallate (PG), against a model gram-positive (Listeria innocua) and the gram-negative bacteria (Escherichia coli O157:H7). Bacterial inactivation kinetic measurements were complemented by characterization of biophysical changes in liposomes, changes in bacterial membrane permeability, morphological changes in bacterial cells, and intracellular oxidative stress upon treatment with PG, LFU, and a combination of PG + LFU. Combination of PG + LFU significantly (>4 log CFU/mL, P < 0.05) enhanced the inactivation of both L. innocua and E. coli O157:H7 compared to PG or LFU treatment. As expected, L. innocua had a significantly higher resistance to inactivation compared to E. coli using a combination of PG + LFU. Biophysical measurements in liposomes, bacterial permeability measurements, and scanning electron microscope (SEM)-based morphological measurements show rapid interactions of PG with membranes. Upon extended treatment of cells with PG + LFU, a significant increase in membrane damage was observed compared to PG or LFU alone. A lack of change in the intracellular thiol content following the combined treatment and limited effectiveness of exogenously added antioxidants in attenuating the synergistic antimicrobial action demonstrated that oxidative stress was not a leading mechanism responsible for the synergistic inactivation by PG + LFU. Overall, the study illustrates synergistic inactivation of bacteria using a combination of PG + LFU based on enhanced membrane damage and its potential for applications in the food and environmental systems.

In Vitro Application of Sonodynamic Antimicrobial Chemotherapy as a Sonobactericidal Therapeutic Approach for Bacterial Infections: A Systematic Review and Meta-analysis

Introduction: This study aimed to perform a systematic review of the literature followed by a meta-analysis about the efficacy of sonodynamic antimicrobial chemotherapy (SACT) in bacterial infections. Methods: According to the PICOS (population, intervention, comparison and outcome) recommendations and PRISMA guidelines, an electronic search was conducted in PubMed, SCOPUS, Embase, and Cochrane Library based on the MeSH terms. All analyses were conducted using Biostat's Comprehensive Meta-Analysis version 2.0. The inter-study heterogeneity and publication bias assessments were carried out on the studies using I2 and the Egger's regression test. Results: Initially, 126 articles were identified in the electronic search, and 14 studies remained after analysis and exclusion of the duplicated studies and eligibility criteria. All results from the included studies displayed a significant reduction of microorganisms. The meta-analysis demonstrated a significant reduction in the bacterial load in all analyses (0.944% [95% CI, 0.901-0.969%; P=0.000]). Also, there was a low risk of bias for microbial load reduction without the evidence of publication bias. Conclusion: The results highlight that there is scientific evidence emphasizing the effectiveness of SACT in reducing the count of microorganisms in bacterial infections.

Escherichia coli inactivation using a hybrid ultrasonic-electrocoagulation reactor

In the current study, a new hybrid ultrasonic-electrocoagulation reactor (U-E reactor) has been used to inactivate Escherichia coli in water. The new hybrid reactor consists of an ultrasonic bath fitted with four perforated aluminium electrodes. These perforated electrodes are designed to act as baffle-plates to enhance the water-mixing process. The electrodes eliminate the need for external mixing devices, which in turn, enhances the cost-effectiveness of the unit. Initially, the ability of the electrocoagulation to inactivate E. coli was optimised for different operating parameters such as electrolysing time (T_e), electrodes spacing (ES) and current density (CD). The ultrasonic field was then applied over different time periods (T_u), during the course of the electrolysing process. Statistical analyses have been conducted to assess the relative effect of each operating parameter on the inactivation of E. coli. An economic study has also been conducted to assess the operating costs of the U-E reactor. The results revealed that the new U-E reactor inactivated 100% of the E. coli within 11 min of electrolysis at ES of 5 mm, CD of 1.5 mA/cm², and an operation cost of 0.212 US $/m³. It was been established that the relative effect of operating parameters on E.coli inactivation followed the order: T_e>T_u>CD>ES.

Low-Frequency Ultrasound Enhances Bactericidal Activity of Antimicrobial Agents against Klebsiella pneumoniae Biofilm

Klebsiella pneumoniae biofilms on inserted devices have been proposed as one of the important factors for hospital-acquired infections, which cause increased resistance to currently used antibiotics. Therefore, it is urgently necessary to develop new treatments with more efficient bacterial clearance. In the present study, we aimed at investigating whether low-frequency ultrasound (LFU) could enhance the bactericidal activity of antimicrobial agents (meropenem (MEM), tigecycline (TGC), fosfomycin (FOM), amikacin (AMK), and colistin (COL)) against K. pneumoniae biofilm infection. K. pneumoniae biofilm was cultivated on the catheter in vitro. Synergistic effects were observed in groups of single ultrasound (S-LFU, 5 min) or multiple ultrasound (M-LFU, 5 min every 8 h (q8h)) in combination with MEM, TGC, and FOM. However, AMK and COL did not show the synergistic effect with either S-LFU or M-LFU. S-LFU in combination with FOM only significantly decreased bacterial counts right after ultrasound, while M-LFU could prolong the synergistic effect until 24 h. The results showed that LFU in combination with antimicrobial agents had a synergistic effect on K. pneumoniae biofilm, and M-LFU might extend the time of synergistic effect compared with S-LFU.

Dark Antibacterial Activity of Rose Bengal

The global spread of bacterial resistance to antibiotics promotes a search for alternative approaches to eradication of pathogenic bacteria. One alternative is using photosensitizers for inhibition of Gram-positive and Gram-negative bacteria under illumination. Due to low penetration of visible light into tissues, applications of photosensitizers are currently limited to treatment of superficial local infections. Excitation of photosensitizers in the dark can be applied to overcome this problem. In the present work, dark antibacterial activity of the photosensitizer Rose Bengal alone and in combination with antibiotics was studied. The minimum inhibitory concentrations (MIC) value of Rose Bengal against S. aureus dropped in the presence of sub-MIC concentrations of ciprofloxacin, levofloxacin, methicillin, and gentamicin. Free Rose Bengal at sub-MIC concentrations can be excited in the dark by ultrasound at 38 kHz. Rose Bengal immobilized onto silicon showed good antibacterial activity in the dark under ultrasonic activation, probably because of Rose Bengal leaching from the polymer during the treatment. Exposure of bacteria to Rose Bengal in the dark under irradiation by electromagnetic radio frequency waves in the 9 to 12 GHz range caused a decrease in the bacterial concentration, presumably due to resonant absorption of electromagnetic energy, its transformation into heat and subsequent excitation of Rose Bengal.

Multiple Low Frequency Ultrasound Enhances Bactericidal Activity of Vancomycin against Methicillin-Resistant Staphylococcus aureus Biofilms

Methicillin-resistant Staphylococcus aureus (MRSA) biofilm infections are difficult to treat due to the high antimicrobial resistance of biofilm. Therefore, new treatments are needed for more effective bacteria clearance. This study was to investigate whether low frequency ultrasound (LFU) can enhance the activity of antimicrobial agents against MRSA biofilm infection. Broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of vancomycin (VAN), linezolid (LIN), and levofloxacin (LEV) against three clinical isolated strains, including one methicillin-susceptible Staphylococcus aureus (MSSA) strain and two MRSA strains. Effects of various influencing factors, such as antimicrobial agents, drug concentrations, ultrasonic intensity, and single (S-LFU, 5 or 15 min) or multiple ultrasound (M-LFU, 5 min every 8 h), on the inhibition of biofilms were investigated. The bactericidal effects of S-LFU or M-LFU on MRSA or MSSA biofilms were determined by colony counts. Right after ultrasound, synergistic effects were observed in groups of S-LFU combined with three antimicrobial agents against MSSA biofilm, but for MRSA biofilm, only S-LFU plus VAN had synergistic effect. At the time point of 24 h, M-LFU plus VAN treatment had synergistic bactericidal effect against MRSA and MSSA biofilms, and the synergy showed that VAN is concentration-dependent, but no synergistic effects were observed in all S-LFU combination groups. In conclusion, combination of M-LFU and antimicrobial agents had a better synergistic effect than S-LFU against MRSA or MSSA biofilm. LFU may be useful in treating biofilm infection in the future.

What Is the Role of Diagnostic and Therapeutic Sonication in Periprosthetic Joint Infections?

BACKGROUND

Periprosthetic joint infection (PJI) is one of the most dreaded complications in joint replacement surgery. Diagnosis and treatment can be difficult and biofilms are of major concern due to their low susceptibility toward antibiotics.

METHODS

This review focuses on the use of sonication as an evolving diagnostic and adjunct treatment modality in the context of PJI. Therapeutic application of sonication is discussed separately for its (i) direct action on bacteria, (ii) synergistic effects with antibiotics, and (iii) effects on release of antibiotics from bone cement.

RESULTS

Used as a diagnostic tool, sonication shows promising results with respect to sensitivity and specificity when compared to conventional methods, notably after previous administration of antibiotics. As an adjunct treatment modality, the chemical, physical, and mechanical effects of sonication are primarily driven by cavitation and recognized as the main cause for bactericidal effects but the exact underlying mechanisms have not been identified yet. Sonication alone does not have the ability to completely eradicate biofilms but synergistic effects when used in conjunction with antibiotics have been reported. There is also evidence for enhanced antibiotic release from bone cement.

CONCLUSION

Sonication is as an evolving modality in the context of PJIs. As a diagnostic tool, it has not been introduced in routine clinical practice and sonication as a treatment modality in PJIs is still in an experimental stage. Factors such as frequency, pressure, chemical activity, intensity, and exposure time need to be evaluated for optimal application of sonication and may also improve study comparison.

A Review of the Combination Therapy of Low Frequency Ultrasound with Antibiotics

Single antimicrobial therapy has been unable to resist the global spread of bacterial resistance. Literatures of available in vitro and in vivo studies were reviewed and the results showed that low frequency ultrasound (LFU) has a promising synergistic bactericidal effect with antibiotics against both planktonic and biofilm bacteria. It also can facilitate the release of antibiotics from medical implants. As a noninvasive and targeted therapy, LFU has great potential in treating bacterial infections. However, more in-depth and detailed studies are still needed before LFU is officially applied as a combination therapy in the field of anti-infective treatment.

Micro/Nanoparticle-Augmented Sonodynamic Therapy (SDT): Breaking the Depth Shallow of Photoactivation

The fast development of photoactivation for cancer treatment provides an efficient photo-therapeutic strategy for cancer treatment, but traditional photodynamic or photothermal therapy suffers from the critical issue of low in vivo penetration depth of tissues. As a non-invasive therapeutic modality, sonodynamic therapy (SDT) can break the depth barrier of photoactivation because ultrasound has an intrinsically high tissue-penetration performance. Micro/nanoparticles can efficiently augment the SDT efficiency based on nanobiotechnology. The state-of-art of the representative achievements on micro/nanoparticle-enhanced SDT is summarized, and specific functions of micro/nanoparticles for SDT are discussed, from the different viewpoints of ultrasound medicine, material science and nanobiotechnology. Emphasis is put on the relationship of structure/composition-SDT performance of micro/nanoparticle-based sonosensitizers. Three types of micro/nanoparticle-augmented SDT are discussed, including organic and inorganic sonosensitizers and micro/nanoparticle-based but sonosensitizer-free strategies to enhance the SDT outcome. SDT-based synergistic cancer therapy augmented by micro/nanoparticles and their biosafety are also included. Some urgent critical issues and potential developments of micro/nanoparticle-augmented SDT for efficient cancer treatment are addressed. It is highly expected that micro/nanoparticle-augmented SDT will be quickly developed as a new and efficient therapeutic modality which will find practical applications in cancer treatment. At the same time, fundamental disciplines regarding materials science, chemistry, medicine and nanotechnology will be advanced.

Low-Frequency Ultrasound Enhances Antimicrobial Activity of Colistin-Vancomycin Combination against Pan-Resistant Biofilm of Acinetobacter baumannii

Acinetobacter baumannii biofilms in catheters are very difficult to treat. Low-frequency ultrasound (LFU) may improve bactericidal or bacteriostatic activity. However, no previous studies have been reported on its efficacy against pan-resistant biofilms of A. baumannii. This study was designed to investigate whether LFU can enhance the activity of colistin, vancomycin and colistin-vancomycin combinations against pan-resistant biofilms of A. baumannii. The efficacy of colistin combinations was determined using the fractional inhibitory concentration index (FICI). The antibacterial effect was determined from bacteria counts in biofilms and the establishment of 24-h time-kill curves. A significantly synergistic effect was detected between colistin and vancomycin (FICI <0.05). We found that although application of LFU (40 kHz, 600 mW/cm(2), 30 min, duty cycle 1:9) alone or in combination with a single agent failed to significantly reduce bacteria counts in biofilms, it apparently enhanced the antibacterial effectiveness of combinations of these agents. Moreover, higher concentrations of colistin in the combination treatments resulted in a better ultrasound-enhanced antibacterial effect. In 24-h time-kill curves, the combination of colistin (8 μg/mL) plus vancomycin (4 μg/mL) with LFU caused a significant reduction in bacteria counts in biofilms after 8 h and a continuing decline until 24 h. Bacterial counts were reduced by 3.77 log(CFU/mL) by LFU plus combinations, compared with combinations without LFU at 24 h. Our results indicate that LFU in combination with colistin plus vancomycin may be useful in treating pan-resistant A. baumannii infections.

Damage Effects on Bacille Calmette-Guérin by Low-Frequency, Low-Intensity Ultrasound: A Pilot Study

OBJECTIVES

To perform an in vitro experimental study of the possible damage effects on Bacille Calmette-Guérin (BCG) by low-frequency (42-kHz) ultrasound (US) irradiation at low spatially and temporally averaged intensities and different exposure times.

METHODS

A 2-mL BCG suspension was added to the wells of a 24-well cell culture plate. Then the samples were randomly divided into 4 groups, each group including 3 wells, with group 1 as a control group and groups 2, 3, and 4, as US treatment groups. The samples for groups 2, 3, and 4 were irradiated with US at 0.13 W/cm(2) for 5 minutes, 0.13 W/cm(2) for 15 minutes, and 1.53 W/cm(2) for 15 minutes, respectively. After irradiation, the temperature, ratio of damage, and structure of the bacteria were examined. The cavitation effect of the device was detected by the passive cavitation detection method.

RESULTS

After US irradiation at the different doses (intensity and exposure time), no significant temperature change was found in all sample suspensions. The ratio of bacterial damage tested by flow cytometry and the optical density of the suspensions as assayed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric method showed that the US-irradiated groups were significantly different from the control group. The BCG damage ratio reached 28% at the intensity of 1.53 W/cm(2). Transmission electron microscopic results showed that the bacterial structure of BCG could be destroyed by low-frequency, low-intensity US.

CONCLUSIONS

Low-frequency, low-intensity US can cause acute injury to BCG, and the degree of injury is closely correlated with the US dose applied.

Bactericidal Effect of Photolysis of H2O2 in Combination with Sonolysis of Water via Hydroxyl Radical Generation

The bactericidal effect of hydroxyl radical (·OH) generated by combination of photolysis of hydrogen peroxide (H₂O₂) and sonolysis of water was examined under the condition in which the yield of ·OH increased additively when H₂O₂ aqueous solution was concomitantly irradiated with laser and ultrasound. The suspension of Staphylococcus aureus mixed with the different concentrations of H₂O₂ was irradiated simultaneously with a laser light (wavelength: 405 nm, irradiance: 46 and 91 mW/cm²) and ultrasound (power: 30 w, frequency: 1.65 MHz) at 20 ± 1°C of the water bulk temperature for 2 min. The combination of laser and ultrasound irradiation significantly reduced the viable bacterial count in comparison with the laser irradiation of H₂O₂ alone. By contrast, the ultrasound irradiation alone exerted almost no bactericidal effect. These results suggested that the combination effect of photolysis of H₂O₂ and sonolysis of water on bactericidal activity was synergistic. A multi-way analysis of variance also revealed that the interaction of H₂O₂ concentration, laser power and ultrasound irradiation significantly affected the bactericidal activity. Since the result of oxidative DNA damage evaluation demonstrated that the combination of laser and ultrasound irradiation significantly induced oxidative damage of bacterial DNA in comparison with the laser irradiation of H₂O₂ alone, it was suggested that the combination effect of photolysis of H₂O₂ and sonolysis of water on bactericidal activity would be exerted via oxidative damage of cellular components such as DNA.

Sonodynamic antimicrobial chemotherapy: First steps towards a sound approach for microbe inactivation

Sonodynamic therapy (SDT) relies on the ability of ultrasound to activate sonosensitisers and trigger the generation of reactive oxygen species (ROS) to achieve cell death. SDT was explored as an anticancer approach until 6 years ago, when its potential application as an antimicrobial strategy was pointed out and the term "sonoantimicrobial chemotherapy" (SACT) was coined. The excellent penetration of ultrasound in liquid media make SACT a particularly promising approach for the non-invasive treatment of deep-seated infections, and for the reduction of bacterial load in turbid water. In this review we provide an account of the brief history of SACT, from its molecular bases to the current state of the art and perspective applications.

Sounding the death knell for microbes?

Over the past 5 years, several studies showed that ultrasound, which is sound with a frequency>20 kHz, is able to kill bacteria by activating molecules termed sonosensitizers (SS) to produce reactive oxygen species, which are toxic to microbes. It is our opinion that this work opens up the potential for the development of a novel form of ultrasound-mediated antimicrobial therapy. Termed sonodynamic antimicrobial chemotherapy (SACT), we define this therapy as a regime where a SS is selectively delivered to target microbial cells and activated by ultrasound to induce the death of those microbial cells. Here, we review recent work on SACT, current understanding of its mechanisms, and future prospects for SACT as a therapeutically viable antimicrobial regime.

Therapeutic ultrasound as a treatment modality for chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a chronic infective, inflammatory upper respiratory disease. While the current medical treatment of CRS focuses on the systemic and topical use of steroids and/or antibiotics, many bacteria residing on mucosal surfaces of patients with CRS exist in a biofilm state, making them resistant to most systemic antibiotics. Alternative therapeutic strategies that include blocking bacterial molecular communication, inhibiting biofilm matrix production and breaking down bacterial biofilms are all being explored. Physical therapies such as therapeutic ultrasound (US) have been advocated and utilized as a treatment modality for CRS for many years. US may have antiinflammatory actions and can also be used for the local delivery of drugs through the skin. Therapeutic US, which has been shown in clinical studies to be an effective treatment for both acute rhinosinusitis and CRS, offers significant potential in CRS management.

Synergistic bactericidal effects and mechanisms of low intensity ultrasound and antibiotics against bacteria: a review

Low intensity ultrasonic therapy is always an important research area of ultrasonic medicine. This review concentrates on low intensity ultrasound enhancing bactericidal action of antibiotics against bacteria in vitro and in vivo, including planktonic bacteria, bacterial biofilms, Chlamydia, and bacteria in implants. These literatures show that low intensity ultrasound alone is not effective in killing bacteria, while the combination of low intensity ultrasound and antibiotics is promising. Low intensity ultrasound facilitating antibiotic treatment is still in its infancy, and still requires a great deal of research in order to develop the technology on medical treatment scale.