Different Aspects of Using Ultrasound to Combat Microorganisms

Growing resistance of microorganisms to antibiotics due to their widespread use has led to multiple bacterial infections posing a serious threat to health and human life. Low-frequency ultrasound is one of physical methods for inactivation of pathogenic microbial cells. Application of ultrasound is safe, demonstrates good tissue penetration without significant attenuation of energy, and does not induce microbial resistance. Bactericidal effect of ultrasound is based on acoustic cavitation—the growth and collapse of microbubbles in a liquid medium, resulting in shock waves, shear forces, and microjets which cause irreversible damage and inactivation of microorganisms. The present review combines and analyzes literature data on in vitro and in vivo studies and summarizes works demonstrating the ability of ultrasound, alone or in combination with other methods, to combat pathogenic microorganisms. The results of various studies presented in this review show that low-frequency ultrasound has a noticeable antimicrobial effect on planktonic cells of microorganisms and biofilms. Ultrasound synergistically enhances the effectiveness of other antibacterial agents and activates molecules called sonosensitizers, resulting in the formation of compounds toxic to microbial cells. Ultrasound can also promote local release of antimicrobial drugs from liposomes, as well as from medical implants.