Microbubble cavitation restores Staphylococcus aureus antibiotic susceptibility in vitro and in a septic arthritis model

Coupling ultrasound-triggered microbubble destruction with antibiotics in diluted synovial fluid leads to the effective clearance of S. aureus in models of septic arthritis Treatment failure in joint infections is associated with fibrinous, antibiotic-resistant, floating and tissue-associated Staphylococcus aureus aggregates formed in synovial fluid (SynF). We explore whether antibiotic activity could be increased against Staphylococcus aureus aggregates using ultrasound-triggered microbubble destruction (UTMD), in vitro and in a porcine model of septic arthritis. In vitro, when bacterially laden SynF is diluted, akin to the dilution achieved clinically with lavage and local injection of antibiotics, amikacin and ultrasound application result in increased bacterial metabolism, aggregate permeabilization, and a 4-5 log decrease in colony forming units, independent of microbubble destruction. Without SynF dilution, amikacin + UTMD does not increase antibiotic activity. Importantly, in the porcine model of septic arthritis, no bacteria are recovered from the SynF after treatment with amikacin and UTMD-ultrasound without UTMD is insufficient. Our data suggest that UTMD + antibiotics may serve as an important adjunct for the treatment of septic arthritis.

Automated summary

Coupling ultrasound-triggered microbubble destruction with antibiotics in diluted synovial fluid effectively clears S. aureus in septic arthritis models. Treatment failure in joint infections is associated with antibiotic-resistant Staphylococcus aureus aggregates formed in synovial fluid. In vitro and porcine model experiments show that ultrasound-triggered microbubble destruction enhances antibiotic activity against Staphylococcus aureus aggregates when synovial fluid is diluted.