Emerging Therapies Using Phage-Derived Enzymes Against Multidrug-Resistant Healthcare Pathogens

Abstract

The global rise of multidrug-resistant (MDR) pathogens has intensified the search for innovative antimicrobial strategies. Among these, phage-derived enzymes, particularly endolysins and depolymerases, have emerged as promising alternatives or adjuncts to conventional antibiotics. This review examines current evidence, mechanisms of action, clinical implications, and future perspectives of phage-derived enzymes for managing MDR infections in healthcare settings. Emphasis is placed on their efficacy, safety, spectrum of activity, and integration into existing clinical guidelines, providing a comprehensive resource for clinicians and researchers confronting the evolving threat of antimicrobial resistance.

Introduction

The alarming proliferation of multidrug-resistant (MDR) bacteria poses critical challenges to modern medicine, undermining the effectiveness of conventional antibiotics and complicating the management of healthcare-associated infections. The World Health Organization has highlighted MDR pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Enterobacterales (CRE), and multidrug-resistant Pseudomonas aeruginosa as urgent public health threats. In this context, the exploration of bacteriophage (phage)-derived enzymes, notably endolysins and depolymerases, represents a rapidly evolving field with significant clinical promise. These enzymes offer targeted lytic activity against bacterial pathogens, circumventing traditional mechanisms of resistance. This article synthesizes current knowledge on the deployment of phage-derived enzymes against MDR organisms, discussing their mechanisms, clinical applications, and integration into evidence-based medical practice.

Epidemiology / Disease Burden

MDR healthcare-associated infections are responsible for significant morbidity, mortality, and healthcare costs globally. The Centers for Disease Control and Prevention (CDC) estimate that in the United States alone, at least 2.8 million people acquire MDR bacterial infections annually, resulting in more than 35,000 deaths. Similar trends are reported in Europe and Asia, with MDR Gram-negative bacteria such as Klebsiella pneumoniae and Acinetobacter baumannii contributing to outbreaks in intensive care units (ICUs) and surgical wards. The burden is exacerbated by limited therapeutic options, prolonged hospitalizations, and increased need for advanced supportive care, underscoring the urgent necessity for novel antimicrobial strategies.

Pathophysiology

The pathophysiology of MDR infections is characterized by the acquisition and expression of genetic determinants that confer resistance to multiple antibiotic classes. These mechanisms include the production of extended-spectrum β-lactamases (ESBLs), carbapenemases, efflux pumps, and modifications to target sites. Phage-derived enzymes, particularly endolysins, act by cleaving peptidoglycan bonds in the bacterial cell wall, leading to rapid cell lysis. Depolymerases degrade extracellular polysaccharides such as biofilm matrices and capsules, enhancing bacterial susceptibility to immune clearance and antimicrobials. Unlike antibiotics, these enzymes demonstrate species-specific activity, minimizing off-target effects on the host microbiota.

Risk Factors

Risk factors for MDR infections include prior exposure to broad-spectrum antibiotics, prolonged hospitalization, presence of invasive devices (e.g., catheters, ventilators), immunosuppression, and exposure to high-risk healthcare environments. Patients in ICUs, oncology wards, and transplant units are particularly vulnerable. Underlying chronic diseases such as diabetes, chronic kidney disease, and advanced age further increase susceptibility. The overuse and misuse of antibiotics in both human and veterinary medicine continue to drive the selection and transmission of resistant organisms.

Clinical Features

MDR bacterial infections can manifest as bloodstream infections, pneumonia, urinary tract infections, wound infections, and device-associated infections. Clinical presentations are often indistinguishable from those caused by susceptible strains but are characterized by poor response to standard antibiotic therapy, rapid progression, and increased risk of complications such as sepsis and organ dysfunction. The presence of biofilms on medical devices complicates eradication, necessitating adjunctive or alternative therapies.

Diagnosis

Accurate and timely diagnosis of MDR infections relies on microbiological cultures, antimicrobial susceptibility testing, and molecular assays to detect resistance genes. Recent advances include multiplex PCR and next-generation sequencing, which enable rapid identification of pathogens and their resistance profiles. Diagnostic stewardship is essential to guide appropriate therapy and to monitor the emergence of resistance during treatment.

Treatment & Management

Traditional management of MDR infections includes the use of last-resort antibiotics such as colistin, tigecycline, and fosfomycin, often in combination regimens. However, the efficacy of these agents is limited by toxicity and the emergence of pan-resistant strains. Supportive care, source control, and removal of infected devices are critical adjuncts. The integration of phage-derived enzymes into clinical protocols is being explored as a means to enhance bacterial clearance, disrupt biofilms, and reduce reliance on toxic antimicrobials.

Recent Advances / Emerging Therapies

Phage-derived enzymes have demonstrated potent antibacterial activity in preclinical and early-phase clinical studies. Endolysins such as CF-301 (exebacase) have shown efficacy against MRSA bacteremia and endocarditis, with improved clinical outcomes when used adjunctively with antibiotics. Depolymerases have been effective in disrupting biofilms and enhancing the activity of host immune defenses and antibiotics against Gram-negative pathogens. Notably, these enzymes retain activity against dormant bacteria within biofilms, addressing a key limitation of conventional antimicrobials. Delivery strategies under investigation include topical, intravenous, inhalational, and device-associated formulations. Early-phase clinical trials report favorable safety profiles, with minimal immunogenicity and low risk of resistance development. Regulatory pathways for compassionate and investigational use are evolving, highlighting the translational potential of these therapies.

Guideline Recommendations

International guidelines, including those from the Infectious Diseases Society of America (IDSA) and European Society of Clinical Microbiology and Infectious Diseases (ESCMID), currently recommend phage therapy and phage-derived enzymes primarily within research or compassionate use frameworks. Ongoing clinical trials and real-world studies are expected to inform future updates. The integration of phage-derived enzymes into antimicrobial stewardship programs is anticipated, particularly for patients with limited therapeutic options or recalcitrant biofilm-associated infections. Multidisciplinary collaboration and robust pharmacovigilance are essential to ensure safe and effective implementation.

Conclusion

The escalating threat of multidrug-resistant healthcare pathogens necessitates innovative and mechanism-driven therapeutic approaches. Phage-derived enzymes represent a scientifically robust and clinically promising strategy to augment existing antimicrobial arsenals. While further research is required to optimize dosing, delivery, and patient selection, current evidence supports their potential role as adjunctive or alternative therapies against MDR infections. Continued collaboration between clinicians, microbiologists, and regulatory bodies will be vital to translating these emerging therapies into routine clinical practice, ultimately improving patient outcomes in the era of antimicrobial resistance.