A Comprehensive Review on Phage Therapy and Phage-Based Drug Development

Phage therapy, the use of bacteriophages (phages) to treat bacterial infections, is regaining momentum as a promising weapon against the rising threat of multidrug-resistant (MDR) bacteria. This comprehensive review explores the historical context, the modern resurgence of phage therapy, and phage-facilitated advancements in medical and technological fields. It details the mechanisms of action and applications of phages in treating MDR bacterial infections, particularly those associated with biofilms and intracellular pathogens. The review further highlights innovative uses of phages in vaccine development, cancer therapy, and as gene delivery vectors. Despite its targeted and efficient approach, phage therapy faces challenges related to phage stability, immune response, and regulatory approval. By examining these areas in detail, this review underscores the immense potential and remaining hurdles in integrating phage-based therapies into modern medical practices.

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

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

Sustained Release of a Streptococcus pneumoniae Endolysin from Liposomes for Potential Otitis Media Treatment

Local delivery of antimicrobials for otitis media treatment would maximize therapeutic efficacy while minimizing side effects. However, drug transport across the tympanic membrane in the absence of a delivery system is challenging. In this study, the MSlys endolysin was encapsulated in deformable liposomes for a targeted treatment of S. pneumoniae, one of the most important causative agents of otitis media. MSlys was successfully encapsulated in liposomes composed of l-alpha-lecithin and sodium cholate (5:1) or l-alpha-lecithin and PEG2000 PE (10:1), with encapsulation efficiencies of about 35%. The PEGylated and sodium cholate liposomes showed, respectively, mean hydrodynamic diameters of 85 and 115 nm and polydispersity indices of 0.32 and 0.42, both being stable after storage at 4 °C for at least one year. Both liposomal formulations showed a sustained release of MSlys over 7 days. Cytotoxicity studies against fibroblast and keratinocyte cell lines revealed the biocompatible nature of both MSlys and MSlys-loaded liposomes. Additionally, the encapsulated MSlys showed prompt antipneumococcal activity against planktonic and biofilm S. pneumoniae, thus holding great potential for transtympanic treatment against S. pneumoniae otitis media.

Emerging medical and engineering strategies for the prevention of long-term indwelling catheter blockage

Urinary catheters have been used on an intermittent or indwelling basis for centuries, in order to relieve urinary retention and incontinence. Nevertheless, the use of urinary catheters in the clinical setting is fraught with complication, the most common of which is the development of nosocomial urinary tract infections, known as catheter-associated urinary tract infections. Infections of this nature are not only significant owing to their high incidence rate and subsequent economic burden but also to the severe medical consecutions that result. A range of techniques have been employed in recent years, utilising various technologies in attempts to counteract the perilous medical cascade following catheter blockage. This review will focus on the current advancement (within the last 10 years) in prevention of encrustation and blockage of long-term indwelling catheters both from engineering and medical perspectives, with particular emphasis on the importance of stimuli-responsive systems.

Enhancing Whole Phage Therapy and Their Derived Antimicrobial Enzymes through Complex Formulation

The resurgence of research into phage biology and therapy is, in part, due to the increasing need for novel agents to treat multidrug-resistant infections. Despite a long clinical history in Eastern Europe and initial success within the food industry, commercialized phage products have yet to enter other sectors. This relative lack of success is, in part, due to the inherent biological limitations of whole phages. These include (but are not limited to) reaching target sites at sufficiently high concentrations to establish an infection which produces enough progeny phages to reduce the bacterial population in a clinically meaningful manner and the limited host range of some phages. Conversely, parallels can be drawn between antimicrobial enzymes derived from phages and conventional antibiotics. In the current article the biological limitations of whole phage-based therapeutics and their derived antimicrobial enzymes will be discussed. In addition, the ability of more complex formulations to address these issues, in the context of medical and non-medical applications, will also be included.

Recombinant Endolysins as Potential Therapeutics against Antibiotic-Resistant Staphylococcus aureus: Current Status of Research and Novel Delivery Strategies

Staphylococcus aureus is one of the most common pathogens of humans and animals, where it frequently colonizes skin and mucosal membranes. It is of major clinical importance as a nosocomial pathogen and causative agent of a wide array of diseases. Multidrug-resistant strains have become increasingly prevalent and represent a leading cause of morbidity and mortality. For this reason, novel strategies to combat multidrug-resistant pathogens are urgently needed. Bacteriophage-derived enzymes, so-called endolysins, and other peptidoglycan hydrolases with the ability to disrupt cell walls represent possible alternatives to conventional antibiotics. These lytic enzymes confer a high degree of host specificity and could potentially replace or be utilized in combination with antibiotics, with the aim to specifically treat infections caused by Gram-positive drug-resistant bacterial pathogens such as methicillin-resistant S. aureus. LysK is one of the best-characterized endolysins with activity against multiple staphylococcal species. Various approaches to further enhance the antibacterial efficacy and applicability of endolysins have been demonstrated. These approaches include the construction of recombinant endolysin derivatives and the development of novel delivery strategies for various applications, such as the production of endolysins in lactic acid bacteria and their conjugation to nanoparticles. These novel strategies are a major focus of this review.