Synergy between induction heating, antibiotics, and N-acetylcysteine eradicates Staphylococcus aureus from biofilm

Abstract

Background: Non-contact induction heating (NCIH) is a noninvasive treatment modality that can be used to cause thermal damage to bacterial biofilms on a metal implant surface in the context of a prosthetic joint infection. The purpose of this study was (1) to determine the effectiveness of NCIH on killing Staphylococcus aureus from biofilm and (2) to determine the possible synergistic effect of NCIH and cocktails of antibiotics and N-acetylcysteine (NAC). Methods: Staphylococcus aureus biofilms were grown on titanium alloy (Ti6Al4V) coupons. These coupons were heated to 50 C, 60 C, 70 C, 80 C, and 90 C for 3.5 min and subsequently exposed to cocktails of vancomycin, rifampicin and NAC at clinically relevant concentrations over 24 h. Results: In the control group without induction heating, 2.2 Ã 10 7 colony forming units (CFU)/cm 2 were observed. At 50 C, 60 C, 70 C, 80 C, and 90 C, a reduction of 0.3-log, 3.9-log, 4.2-log, 4.3-log, and 6.6-log CFU/cm 2 were observed, respectively. There was synergy between antibiotics and induction heating that resulted in less than 100 CFU/cm 2 remaining after 3.5 min at 60 C, and exposure to vancomycin and rifampicin. Total eradication was observed at 80 C. Total eradication was also observed at 60 C and a cocktail of antibiotics with NAC. Conclusion: Induction heating of titanium alloy coupons is effective for the reduction of bacterial load in vitro in S. aureus biofilms. Induction heating and cocktails of antibiotics and NAC have a synergistic effect that results in the total eradication of the biofilm at 60 C and higher for clinically relevant concentrations of vancomycin, rifampicin and NAC. ARTICLE HISTORY

Non-contact induction heating and SAAP-148 eliminate persisters within MRSA biofilms mimicking a metal implant infection

“…Results showed a temperature-dependent reduction in bacterial counts in immature biofilms with complete bacterial eradication seen at a surface temperature of 85 °C, whereas bacterial counts in mature biofilms decreased in a temperaturedependent fashion up to 70 °C and thereafter remained unchanged. The observed effect of NCIH on immature biofilms is in line with an earlier observation that almost all bacteria within 24 h biofilms are eliminated by a heat shock of 85 °C (Pijls et al, 2020). The difference in susceptibility of bacteria in mature and immature biofilms to induction heating could be related to the amount of protective extracellular matrix, which is considerably larger in mature biofilms.…”

“…To heat up the TAN discs in a controlled fashion, a miniaturised version of the NCIH apparatus was built and successfully validated. This equipment was designed to reach a target temperature rather than to maintain the temperature for a prolonged period, as was the case in previous NCIH studies (Pijls et al, 2020). The rationale for this approach was twofold.…”

“…Exposure for longer than 3 min to ~ 80 °C results in elimination of bacteria within biofilms and increased sensitivity of bacteria to antibiotics. Similarly, heating up titanium alloys by NCIH results in a temperature of 80 °C after 3.5 min and almost total eradication of the bacterial load of MRSA 24 h biofilms (Pijls et al, 2020). Moreover, a synergistic effect could be observed upon combination of 60 °C NCIH and antibiotics, resulting in a significant elimination of viable bacteria within biofilms (Pijls et al, 2020).…”

“…Similarly, heating up titanium alloys by NCIH results in a temperature of 80 °C after 3.5 min and almost total eradication of the bacterial load of MRSA 24 h biofilms (Pijls et al, 2020). Moreover, a synergistic effect could be observed upon combination of 60 °C NCIH and antibiotics, resulting in a significant elimination of viable bacteria within biofilms (Pijls et al, 2020). Another alternative strategy for implant-associated infections is the use of antimicrobial peptides such as SAAP .…”

In vitro activity of hyperthermia on swarming motility and antimicrobial susceptibility profiles of Proteus mirabilis isolates

“…In a study in 2017, Ricker and Nuxoll [31] investigated the synergistic effects of heat and antibiotics using ciprofloxacin, tobramycin and erythromycin on P. aeruginosa strains and they reported that combined treatments had synergistic effects for heat shock conditions of 60 C for 5 min to 70 C for 1 min. Recently, Pijls et al [32] investigated the synergistic effects of non-contact induction heating and antibiotic cocktails and reported that a combination of heat plus antibiotics had synergistic effects on Staphylococcus aureus biofilms at 60 C. Both studies achieved promising results; however; they performed their research at high temperatures, which may cause thermal damage to human tissue. Wu et al [33] designed a magnetic nanoparticle platform to investigate the synergistic effects of nanoparticle heating and the antimicrobial drug amoxicillin on H. pylori and reported that this combination increased the susceptibility of H. pylori to amoxicillin due to the destruction of the cell membrane and microbial biofilm at 41 C. In contrast to our study, they used amoxicillin-loaded nanoparticles in their research.…”