Direct-Contact Low-Frequency Ultrasound and Pulse Lavage Eradicates Biofilms on Implant Materials In Vitro

Abstract

Pulse lavage (PL) debridement and ultrasound are both known to be the treatment of biofilm-related periprosthetic joint infection (PJI). However, the efficacy of these in combination is unknown in eradicating biofilm from the orthopaedic metal implant surface. This study was conducted to understand the efficacy of PL and ultrasound in combination in eradicating bacterial biofilms on titanium alloy in vitro. Biofilms of Staphylococcus aureus strains were grown on titanium alloy coupons for 24 h. Then, the coupons were taken to each treatment group: (i) debrided with PL, (ii) exposed to ultrasound, or (iii) exposed to both. An untreated biofilm was set as a control group. Viable plate count and confocal microscopy using live/dead staining was used to measure the amount of biofilm. Viable plate count showed an approximate two-log reduction in CFU/cm2 in PL alone, from an initial cell count on the mental surface of approximately 109 CFU/cm2. The ultrasound caused an approximate seven-log reduction, and the combination group eradicated viable biofilm bacteria completely. Confocal imaging corroborated the CFU data. Our results indicate that PL and ultrasound both are remarkably in eradicating biofilm, and the combination of PL and ultrasound is more effective than alone in reducing biofilm.

Piezoelectric ultrasonic debridement as new tool for biofilm removal from orthopedic implants: A study in vitro

“…show that the combination of PL and sonication is able to completely dislodge the biofilm. 24,31 Moreover, the values of absorbance that we obtained for PL + Sonication groups and PUS + Sonication groups of each material are not statistically different, therefore, the sonication used in our study is able to dislodge the biofilm regardless which lavage/debridement has been used.…”

“…Our results showed PL had approximately a two-log reduction of CFU/mL in all materials compared to the control and this is consistent with previous studies that reported the same reduction. 21,23,24 These studies assess that PL removes a large part of biofilm, but some authors have pointed out that residual bacteria on disks after PL are sufficient to restore a biofilm. 39 Although it is not known which is the minimum bacterial density for an implant to become infected, it is crucial to reduce as much as possible this value.…”

“…The ultrasound technology is starting to get widely used for diagnosing PJI, 27 since low-frequency ultrasound devices are able to eradicate the biofilm from metallic implants (titanium alloy and stainless steel) 24,31 due to cavitation and microstreaming effects. 40 These principles can be exploited with PUS with a PEEK tip vibrating at low-ultrasonic frequency (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36). In our study, PUS showed approximately a four-log reduction of CFU/mL in all materials compared to the control.…”

“…Therefore, the high failure rate of DAIR could be ascribed to the inadequacy of the lavage/debridement type for the biofilm removal, usually performed by pulse lavage (PL) gun. 20 Despite its ability to mechanically remove the biofilm from bone, soft tissues, and prosthetic implants, several in vitro studies have highlighted the inadequacy of PL alone in the complete biofilm removal, [21][22][23][24] suggesting the implementation of other technologies to improve the outcome.…”

“…Recent in vitro studies have demonstrated the complete biofilm removal from metallic implants by a direct-contact low-frequency ultrasound device, operated in tandem with PL. 24,31 Furthermore, a method that involves a piezoelectric ultrasonic device is widely used in oral surgery: this method exploits the microvibrations of the tip of the device at ultrasonic frequency (>20 kHz) to perform efficient and safe osteotomies. 32 This device combined with a plastic tip is also used to remove the plaque from dental implants, as an efficient debridement method.…”