An Enzybiotic Regimen for the Treatment of Methicillin-Resistant Staphylococcus aureus Orthopaedic Device-Related Infection

Abstract

Orthopaedic device-related infection (ODRI) presents a significant challenge to the field of orthopaedic and trauma surgery. Despite extensive treatment involving surgical debridement and prolonged antibiotic therapy, outcomes remain poor. This is largely due to the unique abilities of Staphylococcus aureus, the most common causative agent of ODRI, to establish and protect itself within the host by forming biofilms on implanted devices and staphylococcal abscess communities (SACs). There is a need for novel antimicrobials that can readily target such features. Enzybiotics are a class of antimicrobial enzymes derived from bacteria and bacteriophages, which function by enzymatically degrading bacterial polymers essential to bacterial survival or biofilm formation. Here, we apply an enzybiotic-based combination regimen to a set of in vitro models as well as in a murine ODRI model to evaluate their usefulness in eradicating established S. aureus infection, compared to classical antibiotics. We show that two chimeric endolysins previously selected for their functional efficacy in human serum in combination with a polysaccharide depolymerase reduce bacterial CFU numbers 10,000-fold in a peg model and in an implant model of biofilm. The enzyme combination also completely eradicates S. aureus in a SAC in vitro model where classical antibiotics are ineffective. In an in vivo ODRI model in mice, the antibiofilm effects of this enzyme regimen are further enhanced when combined with a classical gentamicin/vancomycin treatment. In a mouse model of methicillin-resistant S. aureus (MRSA) ODRI following a fracture repair, a combined local enzybiotic/antibiotic treatment regimen showed a significant CFU reduction in the device and the surrounding soft tissue, as well as significant prevention of weight loss. These outcomes were superior to treatment with antibiotics alone. Overall, this study demonstrates that the addition of enzybiotics, which are distinguished by their extremely rapid killing efficacy and antibiofilm activities, can enhance the treatment of severe MRSA ODRI.

An Antibiotic-Loaded Hydrogel Demonstrates Efficacy as Prophylaxis and Treatment in a Large Animal Model of Orthopaedic Device-Related Infection

“…Future directions to improve the hydrogel may be to broaden the spectrum of application of the hydrogel to Gram negative pathogens, and to achieve synergy ( Watanakunakorn and Tisone, 1982 ). In addition, the hydrogel may be suitable for loading with novel antimicrobials, including bacteriophage and phage-derived enzymes such as peptidoglycan hydrolases ( Onsea et al., 2020 ; Rotman et al., 2020 ; Sumrall et al., 2021 ). Increasing the spectrum of targeted pathogens is important to given low virulence infections due to Coagulase-negative Staphylococci and Cutibacterium acnes are increasing being recognised as causes of prosthesis loosening, non-union and post-operative pain ( Foster et al., 2021 ).…”

Translating bacteriophage-derived depolymerases into antibacterial therapeutics: Challenges and prospects

“…To date, the in vivo evaluation of depolymerase efficacy has been limited to animal tests 68 . This section will summarize the preclinical findings of diverse reported recombinant depolymerases against several MDR pathogens in animal infection models ( Table 1 ) 11 , 27 , 28 , 29 , 30 , 31 , 64 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 . In summary, depolymerases with proper dose regimens were safe and effective as antimicrobials in vivo.…”

“…The antibacterial effect was significantly improved in combination treatment compared to the single treatments. 83 …”

“…Most studies targeted systemic infections, mainly based on murine models and few on Galleria mellonella and Zebrafish models. The murine animals were also used to investigate the efficacy of depolymerases against lung infections 29 and fracture-related infections 83 . Other animals, such as rats and chickens, were employed to assess the therapeutic efficacy of depolymerases against intestinal infections 27 , 28 , 78 .…”

Antimicrobial potency, prevention ability, and killing efficacy of daptomycin-loaded versus vancomycin-loaded β-tricalcium phosphate/calcium sulfate for methicillin-resistant Staphylococcus aureus biofilms

“…Tobramycin (TOB, T) and vancomycin (VAN, V) are often administered for MRSA-related infections. However, increasing reports have indicated resistance to TOB ( Zalavras et al, 2004 ; Jackson et al, 2021 ; Sumrall et al, 2021 ). Likewise, although VAN has been considered the “backbone” against MRSA-related infections, serious concerns have been raised regarding its limitations, such as the low therapeutic index, limited tissue penetration, slow bactericidal activity, as well as the increasing reports of resistance and treatment failure ( Bruniera et al, 2015 ).…”