In Vivo Assessment of Phage and Linezolid Based Implant Coatings for Treatment of Methicillin Resistant S. aureus (MRSA) Mediated Orthopaedic Device Related Infections

Phage therapy in prosthetic joint infections caused by Staphylococcus aureus - A literature review

Prosthetic joint infections (PJIs) are dreaded arthroplasty complications often caused by Staphylococcus aureus. Due to methicillin-resistant S. aureus (MRSA) strains or biofilm formation, successful treatment remains difficult. Currently, two-stage revision surgery constitutes the gold standard therapy of PJIs, sometimes replaced or supplemented by debridement, antibiotics, and implant retention (DAIR). Given the dire consequences of therapeutic failure, bacteriophage therapy might be another treatment option. Here we provide a comprehensive literature review addressing the efficacy of phages applied against S. aureus as causative agent of PJIs. The included 17 publications had in common that the applied phages proved to be effective against various S. aureus isolates including MRSA even in biofilms. Experiments with mice, rats, rabbits, and moth larvae confirmed favorable features of phage preparations in PJI treatment in vivo; including its synergistic with antibiotics. Case reports of PJI patients unanimously described the bacterial eradication following, alongside other measures, intravenous and intra-articular phage administration. Generally, no major side effects occurred, but in some cases elevated liver transaminases were observed. To conclude, our review compiled promising evidence suggesting the safety and suitability of phage therapy as an adjuvant to DAIR in S. aureus PJIs, and thus, underscores the significance of further research.

Phage-Based antibacterial hydrogels for bacterial targeting and Ablation: Progress and perspective

The emergence of drug-resistant bacteria makes antibiotics inadequate to treat bacterial infections, which is now a global problem. Phage as a virus with specific recognition ability can effectively kill the bacteria, which is an efficacious antibacterial material to replace antibiotics. Phage-based hydrogels have good biocompatibility and antibacterial effect at the site of infection. Phage hydrogels have remarkable antibacterial effects on targeted bacteria because of their specific targeted bactericidal ability, but there are few reports and reviews on phage hydrogels. This paper discusses the construction method of phage-based antibacterial hydrogels (PAGs), summarizes the advantages related to PAGs and their applications in the direction of wound healing, treating bone bacterial infections, gastrointestinal infection treatment and other application, and finally gives an outlook on the development and research of PAGs.

Innovations in the Isolation and Treatment of Biofilms in Periprosthetic Joint Infection: A Comprehensive Review of Current and Emerging Therapies in Bone and Joint Infection Management

Periprosthetic joint infections (PJIs) are a devastating complication of joint arthroplasty surgeries that are often complicated by biofilm formation. The development of biofilms makes PJI treatment challenging as they create a barrier against antibiotics and host immune responses. This review article provides an overview of the current understanding of biofilm formation, factors that contribute to their production, and the most common organisms involved in this process. This article focuses on the identification of biofilms, as well as current methodologies and emerging therapies in the management of biofilms in PJI.

Feasibility of using bacteriophage therapy to treat Staphylococcal aureus fracture-related infections

OBJECTIVE

Staphylococcus aureus fracture-related infections (FRIs) are associated with significant morbidity in part because conventional antibiotic therapies have limited ability to eradicate S. aureus in sessile states. Therefore, the objective of this study was to assess the feasibility of using Staphylococcal bacteriophages for FRI by testing the activity of a library of Staphylococcal bacteriophage therapeutics against historically preserved S. aureus FRI clinical isolates.

METHODS

Current Procedural Terminology codes were used to identify patients with FRI from January 1, 2021 to December 31, 2021. Preserved S. aureus FRI isolates from the cases were then tested against a library of 51 Staphylococcal bacteriophages from an American company. This was conducted by assessing the ability of bacteriophages to reduce bacterial growth over time. Growth inhibition greater than 16 h was considered adequate for this study.

RESULTS

All of the S. aureus preserved clinical isolates had at least one bacteriophage with robust lytic activity and six bacteriophages (11.8 %) had robust lytic activity to seven or more of the clinical isolates. However, 41 of the bacteriophages (80.4 %) had activity to less than three of the clinical isolates and no bacteriophage had activity to all the clinical isolates.

CONCLUSION

Our findings show that Staphylococcal bacteriophage therapeutics are readily available for S. aureus FRI clinical isolates. However, when correlated with the current barriers to using bacteriophages to treat FRI, designated Staphylococcal bacteriophage cocktails with broad spectrum activity should be created.

Bacteriophage therapy and current delivery strategies for orthopedic infections: A SCOPING review

OBJECTIVES

Interest in phages as adjunctive therapy to treat difficult infections has grown in the last decade. However, phage dosing and delivery for orthopedic infections have not been systematically summarized.

METHODS

Following PRISMA-ScR guidelines, we conducted a SCOPING review through September 1st, 2023, of MEDLINE, Embase, Web of Science Core Collection, and Cochrane Central.

RESULTS

In total, 77 studies were included, of which 19 (24.7%) were in vitro studies, 17 (22.1%) were animal studies, and 41 (53.2%) were studies in humans. A total of 137 contemporary patients receiving phage therapy are described.

CONCLUSIONS

Direct phage delivery remains the most studied form of phage therapy, notably in prosthetic joint infections, osteomyelitis, and diabetic foot ulcers. Available evidence describing phage therapy in humans suggests favorable outcomes for orthopedic infections, though this evidence is composed largely of low-level descriptive studies. Several phage delivery devices have been described, though a lack of comparative and in-human evidence limits their therapeutic application. Limitations to the use of phage therapy for orthopedic infections that need to be overcome include a lack of understanding related to optimal dosing and phage pharmacokinetics, bacterial heterogeneity in an infection episode, and phage therapy toxicity.

Efficacy and clinical potential of phage therapy in treating methicillin-resistant Staphylococcus aureus (MRSA) infections: A review

Staphylococcus aureus infections have already presented a substantial public health challenge, encompassing different clinical manifestations, ranging from bacteremia to sepsis and multi-organ failures. Among these infections, methicillin-resistant S. aureus (MRSA) is particularly alarming due to its well-documented resistance to multiple classes of antibiotics, contributing significantly to global mortality rates. Consequently, the urgent need for effective treatment options has prompted a growing interest in exploring phage therapy as a potential non-antibiotic treatment against MRSA infections. Phages represent a class of highly specific bacterial viruses known for their ability to infect certain bacterial strains. This review paper explores the clinical potential of phages as a treatment for MRSA infections due to their low toxicity and auto-dosing capabilities. The paper also discusses the synergistic effect of phage-antibiotic combination (PAC) and the promising results from in vitro and animal model studies, which could lead to extensive human clinical trials. However, clinicians need to establish and adhere to standard protocols governing phage administration and implementation. Prominent clinical trials are needed to develop and advance phage therapy as a non-antibiotic therapy intervention, meeting regulatory guidelines, logistical requirements, and ethical considerations, potentially revolutionizing the treatment of MRSA infections.

Do bacteriophages have activity in synovial fluid and against synovial fluid induced bacterial aggregates?

Bacteriophage therapy is a promising adjuvant therapy for the treatment of periprosthetic joint infections. However, there is a paucity of knowledge about the activity of bacteriophages in synovial fluid. Therefore, this study evaluated the activity of a clinically used bacteriophage in synovial fluid as well as the ability of that bacteriophage to prevent the formation of and eradicate bacteria in synovial fluid induced aggregates. The results of this study reinforce that synovial fluid induced aggregates form rapidly in numerous synovial fluid concentrations. More importantly, there was a statistically significant reduction in bacteriophage activity in synovial fluid compared to tryptic soy broth (p < 0.05) and the bacteriophage could not prevent the formation synovial fluid induced aggregates. Also the bacteriophage could not significantly reduce the amount of bacteria in the synovial fluid induced aggregates when compared to controls, and this was not secondary to resistance. Rather the reduced activity seems to be caused by bacteriophages being hindered in the ability to attach to bacterial receptors. We hypothesize this occurred because the viscosity of synovial fluid slowed bacteriophage interactions with planktonic bacteria and the synovial fluid polymers obstructed the bacteriophage attachment receptors thereby preventing attachment to bacteria in the aggregates. These findings have clinical ramifications, supporting the use of bacteriophage therapy as an adjunct to surgical interventions and not in isolation, at the nascent stage. While these findings show a shortcoming of bacteriophage therapy in periprosthetic joint infections, the knowledge gained should spearhead further research to ultimately devise effective and reproducible bacteriophage therapeutics.

The stability of Staphylococcal bacteriophage in presence of local vancomycin concentrations used in clinical practice

PURPOSE

To evaluate the stability of a clinically used Staphylococcal bacteriophage with doses of vancomycin that are encountered with local administration of vancomycin for musculoskeletal infections.

METHODS

A Staphylococcal bacteriophage was evaluated for stability in different pH ranges. Then that same bacteriophage was evaluated for stability with different concentrations of vancomycin and with vancomycin biodegradable antibiotic beads.

RESULTS

The bacteriophage had stability within a pH range of 4-10. There was a statistically significant (P < 0.05) decrease in the amount of bacteriophage over 24 h for vancomycin concentrations of 10 mg/mL and 100 mg/mL compared to lower vancomycin concentrations (1 mg/mL, 0.1 mg/mL and normal saline). However, no statistically significant decrease in the amount of bacteriophage was seen with biodegradable vancomycin beads over 24 h.

CONCLUSION

These findings have important clinical ramifications in that they show local administration of bacteriophages with concomitant local vancomycin powder therapy should be avoided. Moreover, these findings should spearhead further research into bacteriophage stability in in vivo environments.

Alginate microbeads and hydrogels delivering meropenem and bacteriophages to treat Pseudomonas aeruginosa fracture-related infections

Bacteriophage (phage) therapy has shown promise in treating fracture-related infection (FRI); however, questions remain regarding phage efficacy against biofilms, phage-antibiotic interaction, administration routes and dosing, and the development of phage resistance. The goal of this study was to develop a dual antibiotic-phage delivery system containing hydrogel and alginate microbeads loaded with a phage cocktail plus meropenem and evaluate efficacy against muti-drug resistant Pseudomonas aeruginosa. Two phages (FJK.R9-30 and MK.R3-15) displayed enhanced antibiotic activity against P. aeruginosa biofilms when tested in combination with meropenem. The antimicrobial activity of both antibiotic and phage was retained for eight days at 37 °C in dual phage and antibiotic loaded hydrogel with microbeads (PA-HM). In a mouse FRI model, phages were recovered from all tissues within all treatment groups receiving dual PA-HM. Moreover, animals that received the dual PA-HM either with or without systemic antibiotics had less incidence of phage resistance and less serum neutralization compared to phages in saline. The dual PA-HM could reduce bacterial load in soft tissue when combined with systemic antibiotics, although the infection was not eradicated. The use of alginate microbeads and injectable hydrogel for controlled release of phages and antibiotics, leads to the reduced development of phage resistance and lower exposure to the adaptive immune system, which highlights the translational potential of the dual PA-HM. However, further optimization of phage therapy and its delivery system is necessary to achieve higher bacterial killing activity in vivo in the future.

Highly Adhesive Antimicrobial Coatings for External Fixation Devices

Pin site infections arise from the use of percutaneous pinning techniques (as seen in skeletal traction, percutaneous fracture pinning, and external fixation for fracture stabilization or complex deformity reconstruction). These sites are niduses for infection because the skin barrier is disrupted, allowing for bacteria to enter a previously privileged area. After external fixation, the rate of pin site infections can reach up to 100%. Following pin site infection, the pin may loosen, causing increased pain (increasing narcotic usage) and decreasing the fixation of the fracture or deformity correction construct. More serious complications include osteomyelitis and deep tissue infections. Due to the morbidity and costs associated with its sequelae, strategies to reduce pin site infections are vital. Current strategies for preventing implant-associated infections include coatings with antibiotics, antimicrobial polymers and peptides, silver, and other antiseptics like chlorhexidine and silver-sulfadiazine. Problems facing the development of antimicrobial coatings on orthopedic implants and, specifically, on pins known as Kirschner wires (or K-wires) include poor adhesion of the drug-eluting layer, which is easily removed by shear forces during the implantation. Development of highly adhesive drug-eluting coatings could therefore lead to improved antimicrobial efficacy of these devices and ultimately reduce the burden of pin site infections. In response to this need, we developed two types of gel coatings: synthetic poly-glycidyl methacrylate-based and natural-chitosan-based. Upon drying, these gel coatings showed strong adhesion to pins and remained undamaged after the application of strong shear forces. We also demonstrated that antibiotics can be incorporated into these gels, and a K-wire with such a coating retained antimicrobial efficacy after drilling into and removal from a bone. Such a coating could be invaluable for K-wires and other orthopedic implants that experience strong shear forces during their implantation.

Outcomes in revision knee arthroplasty: Preventing reoperation for infection Keynote lecture - BASK annual congress 2023

Revision total knee arthroplasty (TKA) patients have a lower survival rate and lower post-surgical outcomes compared to primary TKA patients. Infection and aseptic loosening are the most common reasons for revision and re-revision TKAs, with infection accounting for nearly half of re-revision cases. To prevent infection, patient optimization addressing obesity, diabetes, malnutrition, and smoking cessation is crucial. Advancements in irrigation solutions, antibiotic-impregnated bone fillers, bacteriophage therapy, and electrochemical therapy hold promise for preventing infection. Technical strategies such as obtaining sufficient component fixation, joint line restoration, and using robot assistance may improve revision TKA outcomes. As the burden of revision TKA continues to rise, substantial efforts remain for mitigating future revision TKAs and their associated complications.

Feasibility of Using Bacteriophage Therapy to Reduce Morbidity and Mortality Associated with Spinal Epidural Abscesses

BACKGROUND

The aim of this study was to determine the feasibility of using bacteriophage therapeutics in spinal epidural abscess (SEA) by reviewing the causes and outcomes of SEA at a single institution and testing a bacteriophage for activity against preserved SEA clinical isolates.

MATERIALS AND METHODS

Medical records were reviewed of patients that received incision and drainage for SEA at a single medical center. Causative organisms, incidence of coinciding bacteremia and outcomes were recorded. A subset of SEA patients (N = 11), that had preserved clinical isolates, were assessed to evaluate if a bacteriophage therapeutic had ample activity to those isolates as seen with spot tests and growth inhibition assays.

RESULTS

Staphylococcus aureus was the predominate bacterial cause (71%) and bacteremia was associated with 96% of S. aureus SEA. Over 50% of the patients either died within three months, had recurrence of their infection, required repeat debridement, or had long term sequalae. A single bacteriophage had positive spot tests for all the S. aureus clinical isolates and inhibited bacterial growth for more than 24 hours for 9 of the 11 (82%) clinical isolates.

CONCLUSION

SEA is associated with significant mortality and morbidity making this a potential indication for adjuvant bacteriophage therapeutics. Since S. aureus is the predominate cause of SEA and most cases are associated bacteremia this creates a potential screening and treatment platform for Staphylococcal bacteriophages therapeutics, allowing for potential pilot studies to be devised.

The associations of gut microbiota, endocrine system and bone metabolism

Gut microbiota is of great importance in human health, and its roles in the maintenance of skeletal homeostasis have long been recognized as the "gut-bone axis." Recent evidence has indicated intercorrelations between gut microbiota, endocrine system and bone metabolism. This review article discussed the complex interactions between gut microbiota and bone metabolism-related hormones, including sex steroids, insulin-like growth factors, 5-hydroxytryptamine, parathyroid hormone, glucagon-like peptides, peptide YY, etc. Although the underlying mechanisms still need further investigation, the regulatory effect of gut microbiota on bone health via interplaying with endocrine system may provide a new paradigm for the better management of musculoskeletal disorders.

Development of an innovative in vivo model of PJI treated with DAIR

Introduction

Prosthetic Joint Infection (PJI) are catastrophic complications of joint replacement. Debridement, implant retention, and antibiotic therapy (DAIR) is the usual strategy in acute infections but fails in 45% of MRSA infections. We describe the development of a model of infected arthroplasty in rabbits, treated with debridement and a course of vancomycin with clinically relevant dosage.

Materials and methods

A total of 15 rabbits were assigned to three groups: vancomycin pharmacokinetics (A), infection (B), and DAIR (C). All groups received a tibial arthroplasty using a Ti-6Al-4V implant. Groups B and C were infected per-operatively with a 5.5 log10 MRSA inoculum. After 1 week, groups C infected knees were surgically debrided. Groups A and C received 1 week of vancomycin. Pharmacokinetic profiles were obtained in group A following 1st and 5th injections. Animals were euthanized 2 weeks after the arthroplasty. Implants and tissue samples were processed for bacterial counts and histology.

Results

Average vancomycin AUC_{0–12 h} were 213.0 mg*h/L (1st injection) and 207.8 mg*h/L (5th injection), reaching clinical targets. All inoculated animals were infected. CFUs were reproducible in groups B. A sharp decrease in CFU was observed in groups C. Serum markers and leukocytes counts increased significantly in infected groups.

Conclusion

We developed a reproducible rabbit model of PJI treated with DAIR, using vancomycin at clinically relevant concentrations.

Bacteriophage Therapy in Implant-Related Orthopedic Infections

Biofilm producers pose a major challenge in treating implant-related orthopedic infections (IROIs). The incidence of IROIs for the closed fracture amounts to 1% to 2% whereas for open fracture it is up to 30%. Due to inappropriate and irrational use of antibiotics in the management of infections, there is an emergence of a global "antimicrobial resistance crisis". To combat these antimicrobial resistance crises, a few innovative and targeted therapies like nanomedicine, phage therapy, antimicrobial peptides, and sonic therapies have been introduced. In this review, we have detailed the basic mechanisms involved in the employment of bacteriophage therapy for IROIs, along with the preclinical and clinical data on its utility. We also present the guidelines on its regulation, processing, and limitations of bacteriophage therpay to combat the upcoming era of antibiotic resistance.

The Role of Staphylococcal Biofilm on the Surface of Implants in Orthopedic Infection

Despite advanced implant sterilization and aseptic surgical techniques, implant-associated infection remains a major challenge for orthopedic surgeries. The subject of bacterial biofilms is receiving increasing attention, probably as a result of the wide acknowledgement of the ubiquity of biofilms in the clinical environment, as well as the extreme difficulty in eradicating them. Biofilm can be defined as a structured microbial community of cells that are attached to a substratum and embedded in a matrix of extracellular polymeric substances (EPS) that they have produced. Biofilm development has been proposed as occurring in a multi-step process: (i) attachment and adherence, (ii) accumulation/maturation due to cellular aggregation and EPS production, and (iii) biofilm detachment (also called dispersal) of bacterial cells. In all these stages, characteristic proteinaceous and non-proteinaceous compounds are expressed, and their expression is strictly controlled. Bacterial biofilm formation around implants shelters the bacteria and encourages the persistence of infection, which could lead to implant failure and osteomyelitis. These complications need to be treated by major revision surgeries and extended antibiotic therapies, which could lead to high treatment costs and even increase mortality. Effective preventive and therapeutic measures to reduce risks for implant-associated infections are thus in urgent need.

Benefits of Combined Phage–Antibiotic Therapy for the Control of Antibiotic-Resistant Bacteria: A Literature Review

With the increase in bacterial resistance to antibiotics, more and more therapeutic failures are being reported worldwide. The market for antibiotics is now broken due to the high cost of developing new molecules. A promising solution to bacterial resistance is combined phage–antibiotic therapy, a century-old method that can potentiate existing antibiotics by prolonging or even restoring their activity against specific bacteria. The aim of this literature review was to provide an overview of different phage–antibiotic combinations and to describe the possible mechanisms of phage–antibiotic synergy.

Bacteriophage Therapy for Staphylococcus Aureus Infections: A Review of Animal Models, Treatments, and Clinical Trials

Staphylococcus aureus (S. aureus) is a common and virulent human pathogen causing several serious illnesses including skin abscesses, wound infections, endocarditis, osteomyelitis, pneumonia, and toxic shock syndrome. Antibiotics were first introduced in the 1940s, leading to the belief that bacterial illnesses would be eradicated. However, microorganisms, including S. aureus, began to develop antibiotic resistance from the increased use and abuse of antibiotics. Antibiotic resistance is now one of the most serious threats to global public health. Bacteria like methicillin-resistant Staphylococcus aureus (MRSA) remain a major problem despite several efforts to find new antibiotics. New treatment approaches are required, with bacteriophage treatment, a non-antibiotic strategy to treat bacterial infections, showing particular promise. The ability of S. aureus to resist a wide range of antibiotics makes it an ideal candidate for phage therapy studies. Bacteriophages have a relatively restricted range of action, enabling them to target pathogenic bacteria. Their usage, usually in the form of a cocktail of bacteriophages, allows for more focused treatment while also overcoming the emergence of resistance. However, many obstacles remain, particularly in terms of their effects in vivo, necessitating the development of animal models to assess the bacteriophage efficiency. Here, we provide a review of the animal models, the various clinical case treatments, and clinical trials for S. aureus phage therapy.

Colonization and Infection of Indwelling Medical Devices by Staphylococcus aureus with an Emphasis on Orthopedic Implants

The use of indwelling medical devices has constantly increased in recent years and has revolutionized the quality of life of patients affected by different diseases. However, despite the improvement of hygiene conditions in hospitals, implant-associated infections remain a common and serious complication in prosthetic surgery, mainly in the orthopedic field, where infection often leads to implant failure. Staphylococcus aureus is the most common cause of biomaterial-centered infection. Upon binding to the medical devices, these bacteria proliferate and develop dense communities encased in a protective matrix called biofilm. Biofilm formation has been proposed as occurring in several stages-(1) attachment; (2) proliferation; (3) dispersal-and involves a variety of host and staphylococcal proteinaceous and non-proteinaceous factors. Moreover, biofilm formation is strictly regulated by several control systems. Biofilms enable staphylococci to avoid antimicrobial activity and host immune response and are a source of persistent bacteremia as well as of localized tissue destruction. While considerable information is available on staphylococcal biofilm formation on medical implants and important results have been achieved on the treatment of biofilms, preclinical and clinical applications need to be further investigated. Thus, the purpose of this review is to gather current studies about the mechanism of infection of indwelling medical devices by S. aureus with a special focus on the biochemical factors involved in biofilm formation and regulation. We also provide a summary of the current therapeutic strategies to combat biomaterial-associated infections and highlight the need to further explore biofilm physiology and conduct research for innovative anti-biofilm approaches.

Bacteriophage-Loaded Poly(lactic-co-glycolic acid) Microparticles Mitigate Staphylococcus aureus Infection and Cocultures of Staphylococcus aureus and Pseudomonas aeruginosa

Lung infections caused by Gram-positive Staphylococcus aureus (S. aureus) and coinfections caused by S. aureus and Gram-negative Pseudomonas aeruginosa (P. aeruginosa) are challenging to treat, especially with the rise in the number of antibiotic-resistant strains of these pathogens. Bacteriophage (phage) are bacteria-specific viruses that can infect and lyse bacteria, providing a potentially effective therapy for bacterial infections. However, the development of bacteriophage therapy is impeded by limited suitable biomaterials that can facilitate effective delivery of phage to the lung. Here, the ability of porous microparticles engineered from poly(lactic-co-glycolic acid) (PLGA), a biodegradable polyester, to effectively deliver phage to the lung, is demonstrated. The phage-loaded microparticles (phage-MPs) display potent antimicrobial efficacy against various strains of S. aureus in vitro and in vivo, and arrest the growth of a clinical isolate of S. aureus in the presence of sputum supernatant obtained from cystic fibrosis patients. Moreover, phage-MPs efficiently mitigate in vitro cocultures of S. aureus and P. aeruginosa and display excellent cytocompatibility with human lung epithelial cells. Therefore, phage-MPs represents a promising therapy to treat bacterial lung infection.

Phage–Antibiotic Therapy as a Promising Strategy to Combat Multidrug-Resistant Infections and to Enhance Antimicrobial Efficiency

Infections caused by multidrug-resistant (MDR) bacteria have highlighted the importance of the development of new antimicrobial agents. While bacteriophages (phages) are widely studied as alternative agents to antibiotics, combined treatments using phages and antibiotics have exhibited Phage–Antibiotic Synergy (PAS), in which antibiotics promote phage replication and extraordinary antimicrobial efficacy with reduced development of bacterial resistance. This review paper on the current progress of phage–antibiotic therapy includes aspects of the mechanisms of PAS and the therapeutic performance of PAS in combating multidrug-resistant bacterial infections. The choice of phages and antibiotics, the administration time and sequence, and the concentrations of the two agents impact the bacterial inhibitory effects to different extents.

Bacteriophages and antibiotic interactions in clinical practice: what we have learned so far

Bacteriophages (phages) may be used as an alternative to antibiotic therapy for combating infections caused by multidrug-resistant bacteria. In the last decades, there have been studies concerning the use of phages and antibiotics separately or in combination both in animal models as well as in humans. The phenomenon of phage–antibiotic synergy, in which antibiotics may induce the production of phages by bacterial hosts has been observed. The potential mechanisms of phage and antibiotic synergy was presented in this paper. Studies of a biofilm model showed that a combination of phages with antibiotics may increase removal of bacteria and sequential treatment, consisting of phage administration followed by an antibiotic, was most effective in eliminating biofilms. In vivo studies predominantly show the phenomenon of phage and antibiotic synergy. A few studies also describe antagonism or indifference between phages and antibiotics. Recent papers regarding the application of phages and antibiotics in patients with severe bacterial infections show the effectiveness of simultaneous treatment with both antimicrobials on the clinical outcome.

Global Transcriptomic Response of Staphylococcus aureus to Virulent Bacteriophage Infection

In light of the ever-increasing number of multidrug-resistant bacteria worldwide, bacteriophages are becoming a valid alternative to antibiotics; therefore, their interactions with host bacteria must be thoroughly investigated. Here, we report genome-wide transcriptional changes in a clinical Staphylococcus aureus SA515 strain for three time points after infection with the vB_SauM-515A1 kayvirus. Using an RNA sequencing approach, we identify 263 genes that were differentially expressed (DEGs) between phage-infected and uninfected host samples. Most of the DEGs were identified at an early stage of phage infection and were mainly involved in nucleotide and amino acid metabolism, as well as in cell death prevention. At the subsequent infection stages, the vast majority of DEGs were upregulated. Interestingly, 39 upregulated DEGs were common between the 15th and 30th minutes post-infection, and a substantial number of them belonged to the prophages. Furthermore, some virulence factors were overexpressed at the late infection stage, which necessitates more stringent host strain selection requirements for further use of bacteriophages for therapeutic purposes. Thus, this work allows us to better understand the influence of kayviruses on the metabolic systems of S. aureus and contributes to a better comprehension of phage therapy.

Animal experimental investigation on the efficacy of antibiotic therapy with linezolid, vancomycin, cotrimoxazole, and rifampin in treatment of periprosthetic knee joint infections by MRSA

Aims

Periprosthetic joint infections (PJIs) are rare, but represent a great burden for the patient. In addition, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) is increasing. The aim of this rat experiment was therefore to compare the antibiotics commonly used in the treatment of PJIs caused by MRSA.

Methods

For this purpose, sterilized steel implants were implanted into the femur of 77 rats. The metal devices were inoculated with suspensions of two different MRSA strains. The animals were divided into groups and treated with vancomycin, linezolid, cotrimoxazole, or rifampin as monotherapy, or with combination of antibiotics over a period of 14 days. After a two-day antibiotic-free interval, the implant was explanted, and bone, muscle, and periarticular tissue were microbiologically analyzed.

Results

Vancomycin and linezolid were able to significantly (p < 0.05) reduce the MRSA bacterial count at implants. No significant effect was found at the bone. Rifampin was the only monotherapy that significantly reduced the bacterial count on implant and bone. The combination with vancomycin or linezolid showed significant efficacy. Treatment with cotrimoxazole alone did not achieve a significant bacterial count reduction. The combination of linezolid plus rifampin was significantly more effective on implant and bone than the control group in both trials.

Conclusion

Although rifampicin is effective as a monotherapy, it should not be used because of the high rate of resistance development. Our animal experiments showed the great importance of combination antibiotic therapies. In the future, investigations with higher case numbers, varied bacterial concentrations, and changes in individual drug dosages will be necessary to be able to draw an exact comparison, possibly within a clinical trial.

Cite this article: Bone Joint Res 2022;11(3):143–151.

How Good are Bacteriophages as an Alternative Therapy to Mitigate Biofilms of Nosocomial Infections

Bacteria survive on any surface through the generation of biofilms that provide a protective environment to grow as well as making them drug resistant. Extracellular polymeric matrix is a crucial component in biofilm formation. The presence of biofilms consisting of common opportunistic and nosocomial, drug-resistant pathogens has been reported on medical devices like catheters and prosthetics, leading to many complications. Several approaches are under investigation to combat drug-resistant bacteria. Deployment of bacteriophages is one of the promising approaches to invade biofilm that may expose bacteria to the conditions adverse for their growth. Penetration into these biofilms and their destruction by bacteriophages is brought about due to their small size and ability of their progeny to diffuse through the bacterial cell wall. The other mechanisms employed by phages to infect biofilms may include their relocation through water channels to embedded host cells, replication at local sites followed by infection to the neighboring cells and production of depolymerizing enzymes to decompose viscous biofilm matrix, etc. Various research groups are investigating intricacies involved in phage therapy to mitigate the bacterial infection and biofilm formation. Thus, bacteriophages represent a good control over different biofilms and further understanding of phage-biofilm interaction at molecular level may overcome the clinical challenges in phage therapy. The present review summarizes the comprehensive details on dynamic interaction of phages with bacterial biofilms and the role of phage-derived enzymes - endolysin and depolymerases in extenuating biofilms of clinical and medical concern. The methodology employed was an extensive literature search, using several keywords in important scientific databases, such as Scopus, Web of Science, PubMed, ScienceDirect, etc. The keywords were also used with Boolean operator "And". More than 250 relevant and recent articles were selected and reviewed to discuss the evidence-based data on the application of phage therapy with recent updates, and related potential challenges.

Biomaterial-based delivery of antimicrobial therapies for the treatment of bacterial infections

The rise in antibiotic-resistant bacteria, including strains that are resistant to last-resort antibiotics, and the limited ability of antibiotics to eradicate biofilms, have necessitated the development of alternative antibacterial therapeutics. Antibacterial biomaterials, such as polycationic polymers, and biomaterial-assisted delivery of non-antibiotic therapeutics, such as bacteriophages, antimicrobial peptides and antimicrobial enzymes, have improved our ability to treat antibiotic-resistant and recurring infections. Biomaterials not only allow targeted delivery of multiple agents, but also sustained release at the infection site, thereby reducing potential systemic adverse effects. In this Review, we discuss biomaterial-based non-antibiotic antibacterial therapies for the treatment of community- and hospital-acquired infectious diseases, with a focus in in vivo results. We highlight the translational potential of different biomaterial-based strategies, and provide a perspective on the challenges associated with their clinical translation. Finally, we discuss the future scope of biomaterial-assisted antibacterial therapies.

WEB SUMMARY

The development of antibiotic tolerance and resistance has demanded the search for alternative antibacterial therapies. This Review discusses antibacterial biomaterials and biomaterial-assisted delivery of non-antibiotic therapeutics for the treatment of bacterial infectious diseases, with a focus on clinical translation.

Prospects of Inhaled Phage Therapy for Combatting Pulmonary Infections

With respiratory infections accounting for significant morbidity and mortality, the issue of antibiotic resistance has added to the gravity of the situation. Treatment of pulmonary infections (bacterial pneumonia, cystic fibrosis-associated bacterial infections, tuberculosis) is more challenging with the involvement of multi-drug resistant bacterial strains, which act as etiological agents. Furthermore, with the dearth of new antibiotics available and old antibiotics losing efficacy, it is prudent to switch to non-antibiotic approaches to fight this battle. Phage therapy represents one such approach that has proven effective against a range of bacterial pathogens including drug resistant strains. Inhaled phage therapy encompasses the use of stable phage preparations given via aerosol delivery. This therapy can be used as an adjunct treatment option in both prophylactic and therapeutic modes. In the present review, we first highlight the role and action of phages against pulmonary pathogens, followed by delineating the different methods of delivery of inhaled phage therapy with evidence of success. The review aims to focus on recent advances and developments in improving the final success and outcome of pulmonary phage therapy. It details the use of electrospray for targeted delivery, advances in nebulization techniques, individualized controlled inhalation with software control, and liposome-encapsulated nebulized phages to take pulmonary phage delivery to the next level. The review expands knowledge on the pulmonary delivery of phages and the advances that have been made for improved outcomes in the treatment of respiratory infections.

Bacteriophage Therapy for the Prevention and Treatment of Fracture-Related Infection Caused by Staphylococcus aureus: a Preclinical Study

Although several studies have shown promising clinical outcomes of phage therapy in patients with orthopedic device-related infections, questions remain regarding the optimal application protocol, systemic effects, and the impact of the immune response. This study provides a proof-of-concept of phage therapy in a clinically relevant rabbit model of fracture-related infection (FRI) caused by Staphylococcus aureus. In a prevention setting, phage in saline (without any biomaterial-based carrier) was highly effective in the prevention of FRI, compared to systemic antibiotic prophylaxis alone. In the subsequent study involving treatment of established infection, daily administration of phage in saline through a subcutaneous access tube was compared to a single intraoperative application of a phage-loaded hydrogel and a control group receiving antibiotics only. In this setting, although a possible trend of bacterial load reduction on the implant was observed with the phage-loaded hydrogel, no superior effect of phage therapy was found compared to antibiotic treatment alone. The application of phage in saline through a subcutaneous access tube was, however, complicated by superinfection and the development of neutralizing antibodies. The latter was not found in the animals that received the phage-loaded hydrogel, which may indicate that encapsulation of phages into a carrier such as a hydrogel limits their exposure to the adaptive immune system. These studies show phage therapy can be useful in targeting orthopedic device-related infection, however, further research and improvements of these application methods are required for this complex clinical setting. IMPORTANCE Because of the growing spread of antimicrobial resistance, the use of alternative prevention and treatment strategies is gaining interest. Although the therapeutic potential of bacteriophages has been demonstrated in a number of case reports and series over the past decade, many unanswered questions remain regarding the optimal application protocol. Furthermore, a major concern during phage therapy is the induction of phage neutralizing antibodies. This study aimed at providing a proof-of-concept of phage therapy in a clinically relevant rabbit model of fracture-related infection caused by Staphylococcus aureus. Phage therapy was applied as prophylaxis in a first phase, and as treatment of an established infection in a second phase. The development of phage neutralizing antibodies was evaluated in the treatment study. This study demonstrates that phage therapy can be useful in targeting orthopedic device-related infection, especially as prophylaxis; however, further research and improvements of these application methods are required.

Recent Advances in the Evaluation of Antimicrobial Materials for Resolution of Orthopedic Implant-Associated Infections In Vivo

While orthopedic implant-associated infections are rare, revision surgeries resulting from infections incur considerable healthcare costs and represent a substantial research area clinically, in academia, and in industry. In recent years, there have been numerous advances in the development of antimicrobial strategies for the prevention and treatment of orthopedic implant-associated infections which offer promise to improve the limitations of existing delivery systems through local and controlled release of antimicrobial agents. Prior to translation to in vivo orthopedic implant-associated infection models, the properties (e.g., degradation, antimicrobial activity, biocompatibility) of the antimicrobial materials can be evaluated in subcutaneous implant in vivo models. The antimicrobial materials are then incorporated into in vivo implant models to evaluate the efficacy of using the material to prevent or treat implant-associated infections. Recent technological advances such as 3D-printing, bacterial genomic sequencing, and real-time in vivo imaging of infection and inflammation have contributed to the development of preclinical implant-associated infection models that more effectively recapitulate the clinical presentation of infections and improve the evaluation of antimicrobial materials. This Review highlights the advantages and limitations of antimicrobial materials used in conjunction with orthopedic implants for the prevention and treatment of orthopedic implant-associated infections and discusses how these materials are evaluated in preclinical in vivo models. This analysis serves as a resource for biomaterial researchers in the selection of an appropriate orthopedic implant-associated infection preclinical model to evaluate novel antimicrobial materials.

Preventing Staphylococcus aureus stainless steel-associated infections in orthopedics. A systematic review and meta-analysis of animal literature

Surgical site infection in the presence of orthopedic implants poses significant healthcare and socioeconomic burden. To assess the potential of various prevention strategies against Staphylococcus-induced stainless steel-associated infections, a review of animal evidence was designed. The databases of PubMed, Embase, and CENTRAL were searched until March 10, 2020, for articles including animal models with stainless steel instrumentation and techniques to prevent Staphylococcus infection. We conducted a random-effects meta-analysis of standardized mean differences (SMD) with subgroup analysis linked to various protection strategies and we recorded complications. Quality was assessed with the SYRCLE's risk of bias tool. Twenty-five studies were included. Combined active coating (featuring organic antibacterial compound release) and degradable passive finishing (lipid- or polymer-based structure modification reducing bacterial adhesion) was favored over untreated controls (SMDs for methicillin-sensitive Staphylococcus aureus [MSSA] and methicillin-resistant Staphylococcus aureus [MRSA] were -3.46, 95% CI [-4.53 to -2.4], p < .001 [n = 4 head-to-head comparisons]; and -6.67, 95% CI [-10.53 to -3], p < .001 [n = 5 head-to-head comparisons], respectively). Systemic vitamin D supplementation and systemic antibiotic administration with or without local antibiotics demonstrated favorable outcomes against MSSA infection. On the contrary, no benefit was seen following vaccination. Of note, no side effects were documented. On the basis of data gathered from eight studies, which comprised 294 animals, a bioresorbable polymer- or lipid-based surface modification supplemented with organic coating yielded improved infection-related outcomes against MSSA and MRSA stainless steel infections, and therefore, this strategy could be further investigated in human research.

Nanotechnology Based Approaches in Phage Therapy: Overcoming the Pharmacological Barriers

With the emergence and spread of global antibiotic resistance and the need for searching safer alternatives, there has been resurgence in exploring the use of bacteriophages in the treatment of bacterial infections referred as phage therapy. Although modern phage therapy has come a long way as demonstrated by numerous efficacy studies but the fact remains that till date, phage therapy has not received regulatory approval for human use (except for compassionate use).Thus, to hit the clinical market, the roadblocks need to be seriously addressed and gaps mended with modern solution based technologies. Nanotechnology represents one such ideal and powerful tool for overcoming the pharmacological barriers (low stability, poor in-vivo retention, targeted delivery, neutralisation by immune system etc.) of administered phage preparations.In literature, there are many review articles on nanotechnology and bacteriophages but these are primarily focussed on highlighting the use of lytic and temperate phages in different fields of nano-medicine such as nanoprobes, nanosensors, cancer diagnostics, cancer cell targeting, drug delivery through phage receptors, phage display etc. Reviews specifically focused on the use of nanotechnology driven techniques strictly to improve phage therapy are however limited. Moreover, these review if present have primarily focussed on discussing encapsulation as a primary method for improving the stability and retention of phage(s) in the body.With new advances made in the field of nanotechnology, approaches extend from mere encapsulation to recently adopted newer strategies. The present review gives a detailed insight into the more recent strategies which include 1) use of lipid based nano-carriers (liposomes, transfersomes etc.) 2) adopting microfluidic based approach, surface modification methods to further enhance the efficiency and stability of phage loaded liposomes 3) Nano- emulsification approach with integration of microfluidics for producing multiple emulsions (suitable for phage cocktails) with unique control over size, shape and drop morphology 4) Phage loaded nanofibers produced by electro-spinning and advanced core shell nanofibers for immediate, biphasic and delayed release systems and 5) Smart release drug delivery platforms that allow superior control over dosing and phage release as and when required. All these new advances are aimed at creating a suitable housing system for therapeutic bacteriophage preparations while targeting the multiple issues of phage therapy i.e., improving phage stability and titers, improving in-vivo retention times, acting as suitable delivery systems for sustained release at target site of infection, improved penetration into biofilms and protection from immune cell attack. The present review thus aims at giving a complete insight into the recent advances (2010 onwards) related to various nanotechnology based approaches to address the issues pertaining to phage therapy. This is essential for improving the overall therapeutic index and success of phage therapy for future clinical approval.

The Trace Element Selenium Is Important for Redox Signaling in Phorbol Ester-Differentiated THP-1 Macrophages

Physiological selenium (Se) levels counteract excessive inflammation, with selenoproteins shaping the immunoregulatory cytokine and lipid mediator profile. How exactly differentiation of monocytes into macrophages influences the expression of the selenoproteome in concert with the Se supply remains obscure. THP-1 monocytes were differentiated with phorbol 12-myristate 13-acetate (PMA) into macrophages and (i) the expression of selenoproteins, (ii) differentiation markers, (iii) the activity of NF-κB and NRF2, as well as (iv) lipid mediator profiles were analyzed. Se and differentiation affected the expression of selenoproteins in a heterogeneous manner. GPX4 expression was substantially decreased during differentiation, whereas GPX1 was not affected. Moreover, Se increased the expression of selenoproteins H and F, which was further enhanced by differentiation for selenoprotein F and diminished for selenoprotein H. Notably, LPS-induced expression of NF-κB target genes was facilitated by Se, as was the release of COX- and LOX-derived lipid mediators and substrates required for lipid mediator biosynthesis. This included TXB2, TXB3, 15-HETE, and 12-HEPE, as well as arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Our results indicate that Se enables macrophages to accurately adjust redox-dependent signaling and thereby modulate downstream lipid mediator profiles.

Recent Strategies to Combat Infections from Biofilm-Forming Bacteria on Orthopaedic Implants

Biofilm-related implant infections (BRII) are a disastrous complication of both elective and trauma orthopaedic surgery and occur when an implant becomes colonised by bacteria. The definitive treatment to eradicate the infections once a biofilm has established is surgical excision of the implant and thorough local debridement, but this carries a significant socioeconomic cost, the outcomes for the patient are often poor, and there is a significant risk of recurrence. Due to the large volumes of surgical procedures performed annually involving medical device implantation, both in orthopaedic surgery and healthcare in general, and with the incidence of implant-related infection being as high as 5%, interventions to prevent and treat BRII are a major focus of research. As such, innovation is progressing at a very fast pace; the aim of this study is to review the latest interventions for the prevention and treatment of BRII, with a particular focus on implant-related approaches.

A combination therapy of Phages and Antibiotics: Two is better than one

Emergence of antibiotic resistance presents a major setback to global health, and shortage of antibiotic pipelines has created an urgent need for development of alternative therapeutic strategies. Bacteriophage (phage) therapy is considered as a potential approach for treatment of the increasing number of antibiotic-resistant pathogens. Phage-antibiotic synergy (PAS) refers to sublethal concentrations of certain antibiotics that enhance release of progeny phages from bacterial cells. A combination of phages and antibiotics is a promising strategy to reduce the dose of antibiotics and the development of antibiotic resistance during treatment. In this review, we highlight the state-of-the-art advancements of PAS studies, including the analysis of bacterial-killing enhancement, bacterial resistance reduction, and anti-biofilm effect, at both in vitro and in vivo levels. A comprehensive review of the genetic and molecular mechanisms of phage antibiotic synergy is provided, and synthetic biology approaches used to engineer phages, and design novel therapies and diagnostic tools are discussed. In addition, the role of engineered phages in reducing pathogenicity of bacteria is explored.

Novel strategies to diagnose prosthetic or native bone and joint infections

INTRODUCTION

Bone and Joint Infections (BJI) are medically important, costly and occur in native and prosthetic joints. Arthroplasties will increase significantly in absolute numbers over time as well as the incidence of Prosthetic Joint Infections (PJI). Diagnosis of BJI and PJI is sub-optimal. The available diagnostic tests have variable effectiveness, are often below standard in sensitivity and/or specificity, and carry significant contamination risks during the collection of clinical samples. Improvement of diagnostics is urgently needed.

AREAS COVERED

We provide a narrative review on current and future diagnostic microbiology technologies. Pathogen identification, antibiotic resistance detection, and assessment of the epidemiology of infections via bacterial typing are considered useful for improved patient management. We confirm the continuing importance of culture methods and successful introduction of molecular, mass spectrometry-mediated and next-generation genome sequencing technologies. The diagnostic algorithms for BJI must be better defined, especially in the context of diversity of both disease phenotypes and clinical specimens rendered available.

EXPERT OPINION

Whether interventions in BJI or PJI are surgical or chemo-therapeutic (antibiotics and bacteriophages included), prior sensitive and specific pathogen detection remains a therapy-substantiating necessity. Innovative tests for earlier and more sensitive and specific detection of bacterial pathogens in BJI are urgently needed.

Biomaterials and technologies in the management of periprosthetic infection after total hip arthroplasty: An updated review

Although total hip arthroplasty (THA) is considered one of the most efficacious procedures for managing various hip conditions, failures due to different mechanisms are still being reported. Periprosthetic joint infection (PJI) is one of the devastating causes of failure and revision of THA. PJI carries a burden on the patient, the surgeon, and the health-care system. The diagnosis and management of PJIs carry many morbidities and increased treatment costs. The development of PJI is multifactorial, including issues related to the patient’s general condition, the surgeon’s efficiency, surgical technique, and the implants used. Recent advances in the area of diagnosis and predicting PJI as well as introducing new technologies and biomaterials update for the prevention and treatment of PJI. Local implant coatings, advancement in the bearing surfaces technologies, and new technologies such as immunotherapy and bacteriophage therapy were introduced and suggested as contemporary PJI eradication solutions. In this review, we aimed at discussing some of the newly introduced materials and technologies for the sake of PJI control.

A mouse air pouch model for evaluating the anti-bacterial efficacy of phage MR-5 in resolving skin and soft tissue infection induced by methicillin-resistant Staphylococcus aureus

With the alarming rise in antimicrobial resistance, phage therapy represents a new paradigm for combating antibiotic-resistant infectious diseases that is worth exploring for its clinical success. With this scenario, the present study aimed at evaluating the in vivo potential of phage MR-5 (broad host range Staphylococcus aureus phage) against soft tissue infections induced by methicillin-resistant S. aureus (MRSA). Also, the usefulness of relatively simple murine air pouch as a dual-purpose model (to study both anti-bacterial and anti-inflammatory parameters) in the field of phage therapeutics has been put to test. Murine air pouch model was established with experimental skin infection induced by S. aureus ATCC 43,300 followed by subcutaneous administration of phage alone as well as along with linezolid. Phage MR-5 alone and in combination with linezolid (showing synergy) brought significant reduction in the bacterial load (both extracellular as well as intracellular) that led to faster resolution of pouch infection. The main conclusions surfaced from the present study include the following: (a) murine air pouch model represents a simple useful model (mimicking subcutaneous skin infection) for studying anti-bacterial potencies of drug candidates. Therefore, its use and further adaptations especially in field of phage therapeutics is highly advocated and (b) phage MR-5 proved to be a potential therapeutic candidate against treatment of MRSA-induced skin and soft tissue infections and use of combination therapy is strongly recommended.

Novel therapeutic interventions towards improved management of septic arthritis

Septic arthritis (SA) represents a medical emergency that needs immediate diagnosis and urgent treatment. Despite aggressive treatment and rapid diagnosis of the causative agent, the mortality and lifelong disability, associated with septic arthritis remain high as close to 11%. Moreover, with the rise in drug resistance, the rates of failure of conventional antibiotic therapy have also increased. Among the etiological agents frequently isolated from cases of septic arthritis, Staphylococcus aureus emerges as a dominating pathogen, and to worsen, the rise in methicillin-resistant S. aureus (MRSA) isolates in bone and joint infections is worrisome. MRSA associated cases of septic arthritis exhibit higher mortality, longer hospital stay, and higher treatment failure with poorer clinical outcomes as compared to cases caused by the sensitive strain i.e methicillin-sensitive S. aureus (MSSA).

In addition to this, equal or even greater damage is imposed by the exacerbated immune response mounted by the patient’s body in a futile attempt to eradicate the bacteria. The antibiotic therapy may not be sufficient enough to control the progression of damage to the joint involved thus, adding to higher mortality and disability rates despite the prompt and timely start of treatment. This situation implies that efforts and focus towards studying/understanding new strategies for improved management of sepsis arthritis is prudent and worth exploring.

The review article aims to give a complete insight into the new therapeutic approaches studied by workers lately in this field. To the best of our knowledge studies highlighting the novel therapeutic strategies against septic arthritis are limited in the literature, although articles on pathogenic mechanism and choice of antibiotics for therapy, current treatment algorithms followed have been discussed by workers in the past. The present study presents and discusses the new alternative approaches, their mechanism of action, proof of concept, and work done so far towards their clinical success. This will surely help to enlighten the researchers with comprehensive knowledge of the new interventions that can be used as an adjunct therapy along with conventional treatment protocol for improved success rates.

Characteristics for phage-encoded cell wall hydrolase of LysSAP27 to reduce staphylococcal food poisoning

To reduce staphylococcal food poisoning (SFP), a phage-encoded cell wall hydrolase called endolysin has emerged as an attractive antibacterial agent. In this study, the Staphylococcus aureus infecting phage vB_SauS-SAP27 (ϕSAP27) was isolated from sewage and characterized morphologically and genetically. ϕSAP27 was identified as Siphoviridae temperate phage, with a genome of 43 kbp. A ϕSAP27 endolysin named LysSAP27 was produced recombinantly in Escherichia coli. LysSAP27 exhibited the highest activity at neutral pH and a temperature of 30 °C, and its lytic activity was upregulated by calcium ions. Following optimization of the enzymatic conditions, LysSAP27 was applied to S. aureus-contaminated milk. Treatment with 2 μM LysSAP27 led to a significant bactericidal effect, corresponding to a reduction in bacterial titer by 2.8 log CFU/mL within 1 h and 3.4 log CFU/mL within 2 h. Therefore, LysSAP27 could be used as an effective antimicrobial agent to prevent SFP in food.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10068-021-00910-2.

Toward Designing of Anti-infective Hydrogels for Orthopedic Implants: From Lab to Clinic

An alarming increase in implant failure incidence due to microbial colonization on the administered orthopedic implants has become a horrifying threat to replacement surgeries and related health concerns. In essence, microbial adhesion and its subsequent biofilm formation, antibiotic resistance, and the host immune system's deficiency are the main culprits. An advanced class of biomaterials termed anti-infective hydrogel implant coatings are evolving to subdue these complications. On this account, this review provides an insight into the significance of anti-infective hydrogels for preventing orthopedic implant associated infections to improve the bone healing process. We briefly discuss the clinical course of implant failure, with a prime focus on orthopedic implants. We identify the different anti-infective coating strategies and hence several anti-infective agents which could be incorporated in the hydrogel matrix. The fundamental design criteria to be considered while fabricating anti-infective hydrogels for orthopedic implants will be discussed. We highlight the different hydrogel coatings based on the origin of the polymers involved in light of their antimicrobial efficacy. We summarize the relevant patents reported in the prevention of implant infections, including orthopedics. Finally, the challenges concerning the clinical translation of the aforesaid hydrogels are described, and considerable solutions for improved clinical practice and better future prospects are proposed.

Bacteriophage therapy for bone and joint infections

Antibiotic resistance represents a threat to human health. It has been suggested that by 2050, antibiotic-resistant infections could cause ten million deaths each year. In orthopaedics, many patients undergoing surgery suffer from complications resulting from implant-associated infection. In these circumstances secondary surgery is usually required and chronic and/or relapsing disease may ensue. The development of effective treatments for antibiotic-resistant infections is needed. Recent evidence shows that bacteriophage (phages; viruses that infect bacteria) therapy may represent a viable and successful solution. In this review, a brief description of bone and joint infection and the nature of bacteriophages is presented, as well as a summary of our current knowledge on the use of bacteriophages in the treatment of bacterial infections. We present contemporary published in vitro and in vivo data as well as data from clinical trials, as they relate to bone and joint infections. We discuss the potential use of bacteriophage therapy in orthopaedic infections. This area of research is beginning to reveal successful results, but mostly in nonorthopaedic fields. We believe that bacteriophage therapy has potential therapeutic value for implant-associated infections in orthopaedics. Cite this article: Bone Joint J 2021;103-B(2):234-244.

Characterization of a Novel Bacteriophage Henu2 and Evaluation of the Synergistic Antibacterial Activity of Phage-Antibiotics

Staphylococcus aureus phage Henu2 was isolated from a sewage sample collected in Kaifeng, China, in 2017. In this study, Henu2, a linear double-stranded DNA virus, was sequenced and found to be 43,513 bp long with 35% G + C content and 63 putative open reading frames (ORFs). Phage Henu2 belongs to the family Siphoviridae and possesses an isometric head (63 nm in diameter). The latent time and burst size of Henu2 were approximately 20 min and 7.8 plaque forming unit (PFU)/infected cells. The Henu2 maintained infectivity over a wide range of temperature (10–60 °C) and pH values (4–12). Phylogenetic and comparative genomic analyses indicate that Staphylococcus aureus phage Henu2 should be a new member of the family of Siphoviridae class-II. In this paper, Phage Henu2 alone exhibited weak inhibitory activity on the growth of S. aureus. However, the combination of phage Henu2 and some antibiotics or oxides could effectively inhibit the growth of S. aureus, with a decrease of more than three logs within 24 h in vitro. These results provide useful information that phage Henu2 can be combined with antibiotics to increase the production of phage Henu2 and thus enhance the efficacy of bacterial killing.

New developments in anti-biofilm intervention towards effective management of orthopedic device related infections (ODRI's)

Orthopedic device related infections (ODRI's) represent a difficult to treat situation owing to their biofilm based nature. Biofilm infections once established are difficult to eradicate even with an aggressive treatment regimen due to their recalcitrance towards antibiotics and immune attack. The involvement of antibiotic resistant pathogens as the etiological agent further worsens the overall clinical picture, pressing on the need to look into alternative treatment strategies. The present review highlightes the microbiological challenges associated with treatment of ODRI's due to biofilm formation on the implant surface. Further, it details the newer anti-infective modalities that work either by preventing biofilm formation and/or through effective disruption of the mature biofilms formed on the medical implant. The study, therefore aims to provide a comprehensive insight into the newer anti-biofilm interventions (non-antibiotic approaches) and a better understanding of their mechanism of action essential for improved management of orthopedic implant infections.

The Rationale for Using Bacteriophage to Treat and Prevent Periprosthetic Joint Infections

Prosthetic joint infection (PJI) is a devastating complication after a joint replacement. PJI and its treatment have a high monetary cost, morbidity, and mortality. The lack of success treating PJI with conventional antibiotics alone is related to the presence of bacterial biofilm on medical implants. Consequently, surgical removal of the implant and prolonged intravenous antibiotics to eradicate the infection are necessary prior to re-implanting a new prosthetic joint. Growing clinical data shows that bacterial predators, called bacteriophages (phages), could be an alternative treatment strategy or prophylactic approach for PJI. Phages could further be exploited to degrade biofilms, making bacteria more susceptible to antibiotics and enabling potential combinatorial therapies. Emerging research suggests that phages may also directly interact with the innate immune response. Phage therapy may play an important, and currently understudied, role in the clearance of PJI, and has the potential to treat thousands of patients who would either have to undergo revision surgery to attempt to clear an infections, take antibiotics for a prolonged period to try and suppress the re-emerging infection, or potentially risk losing a limb.

Synergistic activity of phage PEV20-ciprofloxacin combination powder formulation-A proof-of-principle study in a P. aeruginosa lung infection model

Combination treatment using bacteriophage and antibiotics is potentially an advanced approach to combatting antimicrobial-resistant bacterial infections. We have recently developed an inhalable powder by co-spray drying Pseudomonas phage PEV20 with ciprofloxacin. The purpose of this study was to assess the in vivo effect of the powder using a neutropenic mouse model of acute lung infection. The synergistic activity of PEV20 and ciprofloxacin was investigated by infecting mice with P. aeruginosa, then administering freshly spray-dried single PEV20 (10⁶ PFU/mg), single ciprofloxacin (0.33 mg/mg) or combined PEV20-ciprofloxacin treatment using a dry powder insufflator. Lung tissues were then harvested for colony counting and flow cytometry analysis at 24 h post-treatment. PEV20 and ciprofloxacin combination powder significantly reduced the bacterial load of clinical P. aeruginosa strain in mouse lungs by 5.9 log₁₀ (p < 0.005). No obvious reduction in the bacterial load was observed when the animals were treated only with PEV20 or ciprofloxacin. Assessment of immunological responses in the lungs showed reduced inflammation associating with the bactericidal effect of the PEV20-ciprofloxacin powder. In conclusion, this study has demonstrated the synergistic potential of using the combination PEV20-ciprofloxacin powder for P. aeruginosa respiratory infections.

Transcriptional Landscape of Staphylococcus aureus Kayvirus Bacteriophage vB_SauM-515A1

The Twort-like myoviruses (Kayvirus genus) of S. aureus are promising agents for bacteriophage therapy due to a broad host range and high killing activity against clinical isolates. This work improves the current understanding of the phage infection physiology by transcriptome analysis. The expression profiles of a typical member of the Kayvirus genus (vB_SauM-515A1) were obtained at three time-points post-infection using RNA sequencing. A total of 35 transcription units comprising 238 ORFs were established. The sequences for 58 early and 12 late promoters were identified in the phage genome. The early promoters represent the strong sigma-70 promoters consensus sequence and control the host-dependent expression of 26 transcription units (81% of genes). The late promoters exclusively controlled the expression of four transcription units, while the transcription of the other five units was directed by both types of promoters. The characteristic features of late promoters were long -10 box of TGTTATATTA consensus sequence and the absence of -35 boxes. The data obtained are also of general interest, demonstrating a strategy of the phage genome expression with a broad overlap of the early and late transcription phases without any middle transcription, which is unusual for the large phage genomes (>100 kbp).

Emerging Strategies to Combat β-Lactamase Producing ESKAPE Pathogens

Since the discovery of penicillin by Alexander Fleming in 1929 as a therapeutic agent against staphylococci, β-lactam antibiotics (BLAs) remained the most successful antibiotic classes against the majority of bacterial strains, reaching a percentage of 65% of all medical prescriptions. Unfortunately, the emergence and diversification of β-lactamases pose indefinite health issues, limiting the clinical effectiveness of all current BLAs. One solution is to develop β-lactamase inhibitors (BLIs) capable of restoring the activity of β-lactam drugs. In this review, we will briefly present the older and new BLAs classes, their mechanisms of action, and an update of the BLIs capable of restoring the activity of β-lactam drugs against ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens. Subsequently, we will discuss several promising alternative approaches such as bacteriophages, antimicrobial peptides, nanoparticles, CRISPR (clustered regularly interspaced short palindromic repeats) cas technology, or vaccination developed to limit antimicrobial resistance in this endless fight against Gram-negative pathogens.

Contribution of Podoviridae and Myoviridae bacteriophages to the effectiveness of anti-staphylococcal therapeutic cocktails

Bacteriophage therapy is considered one of the most promising therapeutic approaches against multi-drug resistant bacterial infections. Infections caused by Staphylococcus aureus are very efficiently controlled with therapeutic bacteriophage cocktails, containing a number of individual phages infecting a majority of known pathogenic S. aureus strains. We assessed the contribution of individual bacteriophages comprising a therapeutic bacteriophage cocktail against S. aureus in order to optimize its composition. Two lytic bacteriophages vB_SauM-515A1 (Myoviridae) and vB_SauP-436A (Podoviridae) were isolated from the commercial therapeutic cocktail produced by Microgen (Russia). Host ranges of the phages were established on the panel of 75 S. aureus strains. Phage vB_SauM-515A1 lysed 85.3% and vB_SauP-436A lysed 68.0% of the strains, however, vB_SauP-436A was active against four strains resistant to vB_SauM-515A1, as well as to the therapeutic cocktail per se. Suboptimal results of the therapeutic cocktail application were due to extremely low vB_SauP-436A1 content in this composition. Optimization of the phage titers led to an increase in overall cocktail efficiency. Thus, one of the effective ways to optimize the phage cocktails design was demonstrated and realized by using bacteriophages of different families and lytic spectra.