Successful Treatment of a Recalcitrant Staphylococcus epidermidis Prosthetic Knee Infection with Intraoperative Bacteriophage Therapy

Disruption of Biofilm by Bacteriophages in Clinically Relevant Settings

INTRODUCTION

Antibiotic-resistant bacteria are a growing threat to civilian and military health today. Although infections were once easily treatable by antibiotics and wound cleaning, the frequent mutation of bacteria has created strains impermeable to antibiotics and physical attack. Bacteria further their pathogenicity because of their ability to form biofilms on wounds, medical devices, and implant surfaces. Methods for treating biofilms in clinical settings are limited, and when formed by antibiotic-resistant bacteria, can generate chronic infections that are recalcitrant to available therapies. Bacteriophages are natural viral predators of bacteria, and their ability to rapidly destroy their host has led to increased attention in potential phage therapy applications.

MATERIALS AND METHODS

The present article sought to address a knowledge gap in the available literature pertaining to the usage of bacteriophage in clinically relevant settings and the resolution of infections particular to military concerns. PRISMA guidelines were followed for a systematic review of available literature that met the criteria for analysis and inclusion. The research completed for this review article originated from the U.S. Military Academy's library "Scout" search engine, which complies results from 254 available databases (including PubMed, Google Scholar, and SciFinder). The search criteria included original studies that employed bacteriophage use against biofilms, as well as successful phage therapy strategies for combating chronic bacterial infections. We specifically explored the use of bacteriophage against antibiotic- and treatment-resistant bacteria.

RESULTS

A total of 80 studies were identified that met the inclusion criteria following PRISMA guidelines. The application of bacteriophage has been demonstrated to robustly disrupt biofilm growth in wounds and on implant surfaces. When traditional therapies have failed to disrupt biofilms and chronic infections, a combination of these treatments with phage has proven to be effective, often leading to complete wound healing without reinfection.

CONCLUSIONS

This review article examines the available literature where bacteriophages have been utilized to treat biofilms in clinically relevant settings. Specific attention is paid to biofilms on implant medical devices, biofilms formed on wounds, and clinical outcomes, where phage treatment has been efficacious. In addition to the clinical benefit of phage therapies, the military relevance and treatment of combat-related infections is also examined. Phages offer the ability to expand available treatment options in austere environments with relatively low cost and effort, allowing the impacted warfighter to return to duty quicker and healthier.

A review and new perspective on oral bacteriophages: manifestations in the ecology of oral diseases

Objective

To explore the manifestations of bacteriophages in different oral disease ecologies, including periodontal diseases, dental caries, endodontic infections, and oral cancer, as well as to propel phage therapy for safer and more effective clinical application in the field of dentistry.

Methods

In this literature review, we outlined interactions between bacteriophages, bacteria and even oral cells in the oral ecosystem, especially in disease states. We also analyzed the current status and future prospects of phage therapy in the perspective of different oral diseases.

Results

Various oral bacteriophages targeting at periodontal pathogens as Porphyromonas gingivalis, Fusobacterium nucleatum, Treponema denticola and Aggregatibacter actinomycetemcomitans, cariogenic pathogen Streptococcus mutans, endodontic pathogen Enterococcus faecalis were predicted or isolated, providing promising options for phage therapy. In the realm of oral cancer, aside from displaying tumor antigens or participating in tumor-targeted therapies, phage-like particle vaccines demonstrated the potential to prevent oral infections caused by human papillomaviruses (HPVs) associated with head-and-neck cancers.

Conclusion

Due to their intricate interactions with bacteria and oral cells, bacteriophages are closely linked to the progression and regression of diverse oral diseases. And there is an urgent need for research to explore additional possibilities of bacteriophages in the management of oral diseases.

An effective antibiofilm strategy based on bacteriophages armed with silver nanoparticles

The emerging antibiotic resistance in pathogenic bacteria is a key problem in modern medicine that has led to a search for novel therapeutic strategies. A potential approach for managing such bacteria involves the use of their natural killers, namely lytic bacteriophages. Another effective method involves the use of metal nanoparticles with antimicrobial properties. However, the use of lytic phages armed with nanoparticles as an effective antimicrobial strategy, particularly with respect to biofilms, remains unexplored. Here, we show that T7 phages armed with silver nanoparticles exhibit greater efficacy in terms of controlling bacterial biofilm, compared with phages or nanoparticles alone. We initially identified a novel silver nanoparticle-binding peptide, then constructed T7 phages that successfully displayed the peptide on the outer surface of the viral head. These recombinant, AgNP-binding phages could effectively eradicate bacterial biofilm, even when used at low concentrations. Additionally, when used at concentrations that could eradicate bacterial biofilm, T7 phages armed with silver nanoparticles were not toxic to eukaryotic cells. Our results show that the novel combination of lytic phages with phage-bound silver nanoparticles is an effective, synergistic and safe strategy for the treatment of bacterial biofilms.

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 Experience of Bacteriophages in Biofilm-Related Infections

Bacterial infection has always accompanied human beings, causing suffering and death while also contributing to the advancement of medical science. However, the treatment of infections has become more complex in recent times. The increasing resistance of bacterial strains to antibiotics has diminished the effectiveness of the therapeutic arsenal, making it less likely to find the appropriate empiric antibiotic option. Additionally, the development and persistence of bacterial biofilms have become more prevalent, attributed to the greater use of invasive devices that facilitate biofilm formation and the enhanced survival of chronic infection models where biofilm plays a crucial role. Bacteria within biofilms are less susceptible to antibiotics due to physical, chemical, and genetic factors. Bacteriophages, as biological weapons, can overcome both antimicrobial resistance and biofilm protection. In this review, we will analyze the scientific progress achieved in vitro to justify their clinical application. In the absence of scientific evidence, we will compile publications of clinical cases where phages have been used to treat infections related to biofilm. The scientific basis obtained in vitro and the success rate and safety observed in clinical practice should motivate the medical community to conduct clinical trials establishing a protocol for the proper use of bacteriophages.

Phage Therapy as a Novel Therapeutic for the Treatment of Bone and Joint Infections

Solutions for bone and joint infection (BJI) are needed where conventional treatments are inadequate. Bacteriophages (phages) are naturally occurring viruses that infect bacteria and have been harnessed for refractory bone and joint infections (BJI) in many case reports. Here we examine the safety and efficacy of English-language published cases of BJI since 2010 with phage therapy. From 33 reported cases of BJI treated with phage therapy, 29 (87%) achieved microbiological or clinical success, 2 (5.9%) relapsed with the same organisms, and 2 (5.9%) with a different organism. Of these 4 relapses, all but 1 had eventual clinical resolution with additional surgery or phage treatments. Eight out of 33 cases (24%) reported mild, transient adverse events with no serious events reported. Further work is needed to understand the true efficacy of phages and the role of phages in BJI. Opportunities lay ahead for thoughtfully designed clinical trials adapted to individualized therapies.

Improving the safety and efficacy of phage therapy from the perspective of phage-mammal interactions

Phage therapy has re-emerged as a promising solution for combating antimicrobial-resistant bacterial infections. Increasingly, studies have revealed that phages possess therapeutic potential beyond their antimicrobial properties, including regulating the gut microbiome and maintain intestinal homeostasis, as a novel nanocarrier for targeted drug delivery. However, the complexity and unpredictability of phage behavior during treatment pose a significant challenge in clinical practice. The intricate interactions established between phages, humans, and bacteria throughout their long coexistence in the natural ecosystem contribute to the complexity of phage behavior in therapy, raising concerns about their efficacy and safety as therapeutic agents. Revealing the mechanisms by which phages interact with the human body will provide a theoretical basis for increased application of promising phage therapy. In this review, we provide a comprehensive summary of phage-mammal interactions, including signaling pathways, adaptive immunity responses, and phage-mediated anti-inflammatory responses. Then, from the perspective of phage-mammalian immune system interactions, we present the first systematic overview of the factors affecting phage therapy, such as the mode of administration, the physiological status of the patient, and the biological properties of the phage, to offer new insights into phage therapy for various human diseases.

Isolation and in vitro characterization of novel S. epidermidis phages for therapeutic applications

S. epidermidis is an important opportunistic pathogen causing chronic prosthetic joint infections associated with biofilm growth. Increased tolerance to antibiotic therapy often requires prolonged treatment or revision surgery. Phage therapy is currently used as compassionate use therapy and continues to be evaluated for its viability as adjunctive therapy to antibiotic treatment or as an alternative treatment for infections caused by S. epidermidis to prevent relapses. In the present study, we report the isolation and in vitro characterization of three novel lytic S. epidermidis phages. Their genome content analysis indicated the absence of antibiotic resistance genes and virulence factors. Detailed investigation of the phage preparation indicated the absence of any prophage-related contamination and demonstrated the importance of selecting appropriate hosts for phage development from the outset. The isolated phages infect a high proportion of clinically relevant S. epidermidis strains and several other coagulase-negative species growing both in planktonic culture and as a biofilm. Clinical strains differing in their biofilm phenotype and antibiotic resistance profile were selected to further identify possible mechanisms behind increased tolerance to isolated phages.

A Century of Clinical Use of Phages: A Literature Review

Growing antibiotic resistance and the broken antibiotic market have renewed interest in the use of phages, a century-old therapy that fell into oblivion in the West after two decades of promising results. This literature review with a particular focus on French literature aims to complement current scientific databases with medical and non-medical publications on the clinical use of phages. While several cases of successful treatment with phages have been reported, prospective randomized clinical trials are needed to confirm the efficacy of this therapy.

The promising role of bacteriophage therapy in managing total hip and knee arthroplasty related periprosthetic joint infection, a systematic review

PURPOSE

Total hip and knee arthroplasty periprosthetic joint infection (PJI) poses a management dilemma owing to the emergence of resistant organisms. A promising option is Bacteriophage therapy (BT) was used as an adjuvant for PJI management, aiming at treating resistant infections, decreasing morbidity, and mortality. The current review aimed to demonstrate the role and safety of using BT as an adjuvant to treat PJIs.

METHODS

A systematic search was performed through four databases (Embase, PubMed, Web of Science, and Scopus) up to March 2022, according to the predetermined inclusion and exclusion criteria.

RESULTS

Our systematic review included 11 case reports of 13 patients in which 14 joints (11 TKAs and three THAs) were treated. The patients' average age was 73.7 years, underwent an average of 4.5 previous surgeries. The most common organism was the Staphylococcus aureus species. All patients underwent surgical debridement; for the 13 patients, eight received a cocktail, and five received monophage therapy. All patients received postoperative suppressive antibiotic therapy. After an average follow-up of 14.5 months, all patients had satisfactory outcomes. No recurrence of infection in any patient. Transaminitis complicating BT was developed in three patients, needed stoppage in only one, and the condition was reversible and non-life-threatening.

CONCLUSION

BT is a safe and potentially effective adjuvant therapy for treating resistant and relapsing PJIs. However, further investigations are needed to clarify some BT-related issues to create effective and reproducible therapeutics. Furthermore, new ethical regulations should be implemented to facilitate its widespread use.

Bacteriophage therapy for periprosthetic joint infections: Current limitations and research needed to advance this therapeutic

Bacteriophage therapy is a promising treatment for periprosthetic joint infections (PJIs), particularly given these agents have innate abilities to degrade the biofilm matrix and lyse bacteria within. However, many aspects of this therapy are poorly understood causing treatments to lack uniform effectiveness and reproducibility, which is in part a consequence of several inherent limitations to using bacteriophages to treat PJI. Herein, these limitations are discussed as are additional translational research that needs to be conducted to advance this therapeutic. These include determining if bacteria causing PJIs are polyclonal, consequences of bacteriophage attachment receptor phenotypic variations and ramifications of bacteriophage activity when bacteria interact with in vivo macromolecules. Only with the realization of the current limitations and subsequent knowledge gained from translational research will the potential of bacteriophages to reduce the morbidity and mortality in PJI be fully elucidated.

Characterization of a Lytic Bacteriophage vB_SurP-PSU3 Infecting Staphylococcus ureilyticus and Its Efficacy Against Biofilm

In response to the increasing nosocomial infections caused by antimicrobial-resistant coagulase-negative staphylococci (CoNS), bacteriophages (phages) have emerged as an alternative to antibiotics. Staphylococcus ureilyticus, one of the representative species of the CoNS, is now considered a notable pathogen that causes nosocomial bloodstream infections, and its biofilm-forming ability increases pathogenicity and resistance to antimicrobial agents. In this study, a lytic phage infecting S. ureilyticus was newly isolated from wastewater collected from a sewage treatment plant and its biological and antimicrobial characteristics are described. The isolated phage, named vB_SurP-PSU3, was morphologically similar to Podoviridae and could simultaneously lyse some S. warneri strains used in this study. The sequenced genome of the phage consisted of linear dsDNA with 18,146 bp and genome-based phylogeny revealed that vB_SurP-PSU3 belonged to the genus Andhravirus. Although its overall genomic arrangement and contents were similar to those of other members of the Andhravirus, the predicted endolysin of vB_SurP-PSU3 distinctly differed from the other members of the genus. The bacteriolytic activity of vB_SurP-PSU3 was evaluated using S. ureilyticus ATCC 49330, and the phage could efficiently inhibit the planktonic growth of the bacteria. Moreover, the anti-biofilm analysis showed that vB_SurP-PSU3 could prevent the formation of bacterial biofilm and degrade the mature biofilm in vitro. In an additional cytotoxicity assay of vB_SurP-PSU3, no significant adverse effects were observed on the tested cell. Based on these findings, the newly isolated phage vB_SurP-PSU3 could be classified as a new member of Andhravirus and could be considered an alternative potential biocontrol agent against S. ureilyticus infections and its biofilm.

Salphage: Salvage Bacteriophage Therapy for Recalcitrant MRSA Prosthetic Joint Infection

Prosthetic joint infections are a devastating complication of joint replacement surgery. Consequently, novel therapeutics are needed to thwart the significant morbidity and enormous financial ramifications that are associated with conventional treatments. One such promising adjuvant therapeutic is bacteriophage therapy given its antibiofilm activity and its ability to self-replicate. Herein we discuss the case of a 70-year-old female who had a recalcitrant MRSA prosthetic knee and femoral lateral plate infection who was successfully treated with adjuvant bacteriophage therapy. Moreover, this case discusses the importance of propagating bacteriophage therapeutics on bacteria that are devoid of toxins and the need to ensure bacteriophage activity to all bacterial morphologies. Overall, this case reinforces the potential benefit of using personalized bacteriophage therapy for recalcitrant prosthetic joint infections, but more translational research is needed to thereby devise effective, reproducible clinical trials.

Bacteriophage-Mediated Control of Biofilm: A Promising New Dawn for the Future

Biofilms are complex microbial microcolonies consisting of planktonic and dormant bacteria bound to a surface. The bacterial cells within the biofilm are embedded within the extracellular polymeric substance (EPS) consisting mainly of exopolysaccharides, secreted proteins, lipids, and extracellular DNA. This structural matrix poses a major challenge against common treatment options due to its extensive antibiotic-resistant properties. Because biofilms are so recalcitrant to antibiotics, they pose a unique challenge to patients in a nosocomial setting, mainly linked to lower respiratory, urinary tract, and surgical wound infections as well as the medical devices used during treatment. Another unique property of biofilm is its ability to adhere to both biological and man-made surfaces, allowing growth on human tissues and organs, hospital tools, and medical devices, etc. Based on prior understanding of bacteriophage structure, mechanisms, and its effects on bacteria eradication, leading research has been conducted on the effects of phages and its individual proteins on biofilm and its role in overall biofilm removal while also revealing the obstacles this form of treatment currently have. The expansion in the phage host-species range is one that urges for improvement and is the focus for future studies. This review aims to demonstrate the advantages and challenges of bacteriophage and its components on biofilm removal, as well as potential usage of phage cocktail, combination therapy, and genetically modified phages in a clinical setting.

Assessment of Staphylococcal Clinical Isolates from Periprosthetic Joint Infections for Potential Bacteriophage Therapy

BACKGROUND

Bacteriophage therapy is a potential adjunctive treatment for periprosthetic joint infections (PJIs) given the capabilities of bacteriophages to degrade biofilms, self-replicate, and lyse bacteria. However, many aspects of this therapeutic are ill-defined, and the narrow spectrum of bacteriophage activity along with limited available bacteriophage strains curb potential use for specific bacteria such as Staphylococcus aureus at the present time. Therefore, the aim of this study was to determine the feasibility of using bacteriophages for PJI by (1) categorizing the causative organisms in hip and knee PJI at a tertiary academic center and (2) evaluating in vitro activity of a group of bacteriophages against clinical S. aureus PJI isolates.

METHODS

Patients with chronic hip or knee PJI after undergoing the first stage of a 2-stage revision protocol from 2017 to 2020 were identified retrospectively by a query of the hospital billing database. The causative pathogens in 129 cases were reviewed and categorized. From this cohort, preserved S. aureus isolates were tested against a library of 15 staphylococcal bacteriophages to evaluate for bacterial growth inhibition over 48 hours.

RESULTS

S. aureus was the most common pathogen causing PJI (26% [33] of 129 cases). Of 29 S. aureus samples that were analyzed for bacteriophage activity, 97% showed adequate growth inhibition of the predominant planktonic colonies by at least 1 bacteriophage strain. However, 24% of the 29 samples demonstrated additional smaller, slower-growing S. aureus colonies, none of which had adequate growth inhibition by any of the initial 14 bacteriophages. Of 5 secondary colonies that underwent subsequent testing with another bacteriophage with enhanced biofilm activity, 4 showed adequate growth inhibition.

CONCLUSIONS

Effective bacteriophage therapeutics are potentially available for S. aureus PJI isolates. The differences in bacteriophage activity against the presumed small-colony variants compared with the planktonic isolates have important clinical implications. This finding suggests that bacteriophage attachment receptors differ between the different bacterial morphologic states, and supports future in vitro testing of bacteriophage therapeutics against both planktonic and stationary states of PJI clinical isolates to ensure activity.

Human Plasma Significantly Reduces Bacteriophage Infectivity Against Staphylococcus aureus Clinical Isolates

Bacteriophage therapy has been regaining interest as a potential therapeutic in treating a wide range of infections. However, there is a paucity of knowledge regarding numerous aspects of bacteriophage therapy, thereby hindering the development of proper treatment protocols and effective clinical trials. In this report, the activities of three bacteriophages are evaluated against clinical bacterial isolates in the presence and absence of human plasma (HP). The bacteriophages used in this experiment were residual therapeutic doses from the United States Food and Drug Administration (FDA) approved compassionate use cases to treat recalcitrant prosthetic joint infections (PJIs). Herein we demonstrate that in the presence of HP, the infectivity of these Staphylococcal bacteriophages was significantly reduced compared to the infectivity in the absence of HP. Inhibition of infectivity ranged from 48% to 81% for two methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates independently infected with the same bacteriophage and 98% for a third MRSA clinical isolate infected with a different bacteriophage. In contrast, bacteriophage infectivity of an Enterococcus faecalis clinical isolate was not affected by the presence of HP. We hypothesize that the inhibition is correlated with plasma proteins binding to Staphylococcal surface proteins masking the receptors associated with bacteriophage attachment, thereby reducing infectivity. This has clinical ramifications for bacteriophage therapy use in treating Staphylococcal bacteremia and periprosthetic joint infections.

Considerations for the Use of Phage Therapy in Clinical Practice

Increasing antimicrobial resistance and medical device-related infections have led to a renewed interest in phage therapy as an alternative or adjunct to conventional antimicrobials. Expanded access and compassionate use cases have risen exponentially but have varied widely in approach, methodology, and clinical situations in which phage therapy might be considered. Large gaps in knowledge contribute to heterogeneity in approach and lack of consensus in many important clinical areas. The Antibacterial Resistance Leadership Group (ARLG) has convened a panel of experts in phage therapy, clinical microbiology, infectious diseases, and pharmacology, who worked with regulatory experts and a funding agency to identify questions based on a clinical framework and divided them into three themes: potential clinical situations in which phage therapy might be considered, laboratory testing, and pharmacokinetic considerations. Suggestions are provided as answers to a series of questions intended to inform clinicians considering experimental phage therapy for patients in their clinical practices.

Phage Activity against Planktonic and Biofilm Staphylococcus aureus Periprosthetic Joint Infection Isolates

We recently reported the successful treatment of a case of periprosthetic joint infection (PJI) with phage. Phage activity against bacteria causing PJI has not been systematically evaluated. Here, we examined the in vitro activity of seven phages against 122 clinical isolates of Staphylococcus aureus recovered between April 1999 and February 2018 from subjects with PJI. Phages were assessed against planktonic and biofilm phenotypes. Activity of individual phages was demonstrated against up to 73% of bacterial isolates in the planktonic state and up to 100% of biofilms formed by isolates that were planktonically phage susceptible. Susceptibility to phage was not correlated with small-colony-variant phenotype for planktonic or biofilm bacteria; correlation between antibiotic susceptibility and planktonic phage susceptibility and between biofilm phage susceptibility and strength of biofilm formation were noted under select conditions. These results demonstrate that phages can infect S. aureus causing PJI in both planktonic and biofilm phenotypes, and thus are worthy of investigation as an alternative or addition to antibiotics in this setting.

A systematic review of phage therapy applied to bone and joint infections: an analysis of success rates, treatment modalities and safety

Bone and joint infections are difficult to treat, and increasing antibiotic resistance has only made them more challenging. This has led to renewed interest in phage therapy (PT). The aim of this systematic review was to determine success rate, current treatment modalities and safety of PT in bone and joint infections.A systematic search of PubMed, EMBASE and Cochrane databases as well as the journal PHAGE for literature published between January 2000 and April 2021 was conducted according to PRISMA guidelines to identify all human studies assessing bacteriophages as therapy for bone and joint infections. All study designs and patient populations were eligible. The review's primary outcome was success rate.Twenty records describing a total of 51 patients and 52 treatment episodes were included. No randomized controlled studies were identified. The overall success rate was 71% (n = 37/52). Topical administration alone was the most frequent administration route (85%, n = 44/52). Antibiotics were administered concomitantly with PT in the majority of treatments (79%, n = 41/52), and surgery was performed for 87% (n = 45/52) of treatment episodes. Four minor adverse events related to PT were reported, representing 8% (n = 4/52) of treatment episodes.PT for bone and joint infections has not been evaluated in any randomized controlled clinical study, and current administration modalities are highly variable between case reports and case series. While publications included here show potential benefit and few adverse effects, clinical trials are warranted to assess the efficacy of PT for bone and joint infections and determine optimal treatment modalities. Cite this article: EFORT Open Rev 2021;6:1148-1156. DOI: 10.1302/2058-5241.6.210073.

Phage therapeutics: from promises to practices and prospectives

The rise in multi-drug resistant bacteria and the inability to develop novel antibacterial agents limits our arsenal against infectious diseases. Antibiotic resistance is a global issue requiring an immediate solution, including the development of new antibiotic molecules and other alternative modes of therapy. This article highlights the mechanism of bacteriophage treatment that makes it a real solution for multidrug-resistant infectious diseases. Several case reports identified phage therapy as a potential solution to the emerging challenge of multi-drug resistance. Bacteriophages, unlike antibiotics, have special features, such as host specificity and do not impact other commensals. A new outlook has also arisen with recent advancements in the understanding of phage immunobiology, where phages are repurposed against both bacterial and viral infections. Thus, the potential possibility of phages in COVID-19 patients with secondary bacterial infections has been briefly elucidated. However, significant obstacles that need to be addressed are to design better clinical studies that may contribute to the widespread use of bacteriophage therapy against multi-drug resistant pathogens. In conclusion, antibacterial agents can be used with bacteriophages, i.e. bacteriophage-antibiotic combination therapy, or they can be administered alone in cases when antibiotics are ineffective.

Key points

• AMR, a consequence of antibiotic generated menace globally, has led to the resurgence of phage therapy as an effective and sustainable solution without any side effects and high specificity against refractory MDR bacterial infections.

• Bacteriophages have fewer adverse reactions and can thus be used as monotherapy as well as in conjunction with antibiotics.

• In the context of the COVID-19 pandemic, phage therapy may be a viable option.

Friends or Foes? Rapid Determination of Dissimilar Colistin and Ciprofloxacin Antagonism of Pseudomonas aeruginosa Phages

Phage therapy is a century-old technique employing viruses (phages) to treat bacterial infections, and in the clinic it is often used in combination with antibiotics. Antibiotics, however, interfere with critical bacterial metabolic activities that can be required by phages. Explicit testing of antibiotic antagonism of phage infection activities, though, is not a common feature of phage therapy studies. Here we use optical density-based 'lysis-profile' assays to assess the impact of two antibiotics, colistin and ciprofloxacin, on the bactericidal, bacteriolytic, and new-virion-production activities of three Pseudomonas aeruginosa phages. Though phages and antibiotics in combination are more potent in killing P. aeruginosa than either acting alone, colistin nevertheless substantially interferes with phage bacteriolytic and virion-production activities even at its minimum inhibitory concentration (1× MIC). Ciprofloxacin, by contrast, has little anti-phage impact at 1× or 3× MIC. We corroborate these results with more traditional measures, particularly colony-forming units, plaque-forming units, and one-step growth experiments. Our results suggest that ciprofloxacin could be useful as a concurrent phage therapy co-treatment especially when phage replication is required for treatment success. Lysis-profile assays also appear to be useful, fast, and high-throughput means of assessing antibiotic antagonism of phage infection activities.

Phage Therapy in the 21st Century: Is There Modern, Clinical Evidence of Phage-Mediated Efficacy?

Many bacteriophages are obligate killers of bacteria. That this property could be medically useful was first recognized over one hundred years ago, with 2021 being the 100-year anniversary of the first clinical phage therapy publication. Here we consider modern use of phages in clinical settings. Our aim is to answer one question: do phages serve as effective anti-bacterial infection agents when used clinically? An important emphasis of our analyses is on whether phage therapy-associated anti-bacterial infection efficacy can be reasonably distinguished from that associated with often coadministered antibiotics. We find that about half of 70 human phage treatment reports-published in English thus far in the 2000s-are suggestive of phage-mediated anti-bacterial infection efficacy. Two of these are randomized, double-blinded, infection-treatment studies while 14 of those studies, in our opinion, provide superior evidence of a phage role in observed treatment successes. Roughly three-quarters of these potentially phage-mediated outcomes are based on microbiological as well as clinical results, with the rest based on clinical success. Since many of these phage treatments are of infections for which antibiotic therapy had not been successful, their collective effectiveness is suggestive of a valid utility in employing phages to treat otherwise difficult-to-cure bacterial infections.

Antibiotics- and Heavy Metals-Based Titanium Alloy Surface Modifications for Local Prosthetic Joint Infections

Prosthetic joint infection (PJI) is the second most common cause of arthroplasty failure. Though infrequent, it is one of the most devastating complications since it is associated with great personal cost for the patient and a high economic burden for health systems. Due to the high number of patients that will eventually receive a prosthesis, PJI incidence is increasing exponentially. As these infections are provoked by microorganisms, mainly bacteria, and as such can develop a biofilm, which is in turn resistant to both antibiotics and the immune system, prevention is the ideal approach. However, conventional preventative strategies seem to have reached their limit. Novel prevention strategies fall within two broad categories: (1) antibiotic- and (2) heavy metal-based surface modifications of titanium alloy prostheses. This review examines research on the most relevant titanium alloy surface modifications that use antibiotics to locally prevent primary PJI.

Antimicrobial efficacy and activity perseverance in arthroplasty of calcium sulfate beads containing vancomycin prepared ahead of time and stored in ready-to-use formula

The use of local therapy with antibiotics in a suitable carrier is essential in the treatment and prevention of infections in orthopedic surgery and traumatology. In our orthopedic surgery department, a synthetic calcium sulfate hemihydrate (CaSO₄·½H₂O) is used as an antibiotic carrier, enabling the application of most types of intravenous antibiotics in the form of powder and liquid. This type of carrier with antibiotics is prepared in the theater during the procedure. During a surgical procedure, a small dead space is created (hand and foot area), which must be filled with an antibiotic carrier, and the situations arise where a large amount of the carrier is not used and thrown away. Therefore, we verified the efficacy of vancomycin in the pre-prepared carrier by an orientation microbiological method and by measuring the concentrations of the vancomycin released in active form and its two crystalline degradation products. Based on the agar diffusion test, we did not measure any difference in the effectiveness of the antibiotic in the carrier after its 12-day storage. Although vancomycin concentrations decreased by approximately 32% at the end of 12 days of storage, the concentrations of the released active form of vancomycin are many times higher than the minimum inhibitory concentrations for resistant strains of Staphylococcus aureus. Thus, the calcium sulfate carrier with vancomycin can be prepared several days in advance before its application, certainly up to 12 days.

Successful Treatment of Staphylococcus aureus Prosthetic Joint Infection with Bacteriophage Therapy

Successful joint replacement is a life-enhancing procedure with significant growth in the past decade. Prosthetic joint infection occurs rarely; it is a biofilm-based infection that is poorly responsive to antibiotic alone. Recent interest in bacteriophage therapy has made it possible to treat some biofilm-based infections, as well as those caused by multidrug-resistant pathogens, successfully when conventional antibiotic therapy has failed. Here, we describe the case of a 61-year-old woman who was successfully treated after a second cycle of bacteriophage therapy administered at the time of a two-stage exchange procedure for a persistent methicillin-sensitive Staphylococcus aureus (MSSA) prosthetic knee-joint infection. We highlight the safety and efficacy of both intravenous and intra-articular infusions of bacteriophage therapy, a successful outcome with a single lytic phage, and the development of serum neutralization with prolonged treatment.

Potential Use of Adjuvant Bacteriophage Therapy With Debridement, Antibiotics, and Implant Retention Surgery to Treat Chronic Prosthetic Joint Infections

The number of arthroplasties conducted annually continues to increase; however, approximately 1%–2% of all knee and hip arthroplasties will become infected. These prosthetic joint infections are costly, difficult to treat, and cause significant morbidity and mortality as a direct result of conventional surgical and medical managements. In this perspective, we discuss factors that make these infections arduous to treat as well as the potential use of adjuvant bacteriophage therapy with debridement, antibiotics, and implant retention surgery to cure these infections without removing the infected prosthesis. We also provide rationale as to why future clinical trials evaluating this novel therapeutic will need to be designed as noninferiority trials, and we compare this approach to 2-stage revision surgery. If bacteriophage therapy continues to show effectiveness, this could revolutionize the treatment of prosthetic joint infections and pioneer new treatments for similar infections.