A team of doctors and researchers working at Erasmus Hospital in Belgium has successfully treated an adult woman infected with a drug-resistant bacteria using a combination of bacteriophage therapy and antibiotics.
In their paper published in the journal Nature Communications, the group describes the reasons for the use of the treatment and the ways it might be used in other cases.
Bacteriophages are viruses that infect and kill bacteria. Research involving their use in human patients has been ongoing for several decades, but they are still not used to treat patients. In this new effort, the researchers were presented with a unique opportunity not only to treat a patient in need of help, but to learn more about the possible use of viruses to treat patients infected with bacteria that have become resistant to conventional antibiotics.
In this case, the patient had been severely injured by a terrorist’s bomb—she suffered multiple injuries, including damage to her leg. Doctors treating her had to remove some of the bone, which led to a bacterial infection. Unfortunately for the patient, the bacteria was Klebsiella pneumoniae, which is known to be resistant to antibiotics, and it also creates films that make it difficult for antibiotics to reach infected areas.
Over the course of several years, the researchers tried multiple ways to rid the patient of the infection, to no avail. Her medical team, finding no other options, chose to pursue bacteriophage therapy. To that end, they asked for assistance from a team at the Eliava Institute in Tbilisi that has been studying bacteriophage therapy for many years.
To use a bacteriophage, a virus must be found that attacks the exact strain of bacteria behind an infection. The researchers conducted an exhaustive search and test regimen until finally coming across a virus they found in a sample of sewer water. The virus was cultured and then mixed into a liquid solution that was applied directly to the infected site on the patient’s leg.
They also administered a host of antibacterial agents. The patient finally began recovering from her infection, and over a period of three years, she recovered to the point that she was not only free of the bacterial infection, but able to walk again.
The researchers suggest that bacteriophage therapy is a viable treatment for bacterial infections, though they note that before it can be considered as an alternative therapy for infected patients, a better means of finding bacteriophages must be found.
It is estimated that antibiotic-resistant bacterial strains account for approximately 33,000 annual deaths in Europe, emphasizing the urgent need for devising novel strategies to tackle this global challenge . The ability of bacteria to acquire drug resistance through random mutation as well as conjugation-mediated genetic transfer has made bacterial infection and contamination a major concern with far reaching implications.
Pseudomonas aeruginosa strains have been shown to become resistant to colistin through cross-species plasmid transfer of the MCR-1 gene from resistant strains of Escherichia coli . Other examples of antibiotic-resistant superbugs include methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus (VRE) and multi-drug-resistant Mycobacterium tuberculosis . The spread of resistance has resulted in the emergence of ‘superbugs’, responsible for an increase in deaths from illnesses previously treatable with conventional antibiotics [4,5,6,7,8].
The search for alternative strategies to solve these problems has rekindled interest in bacteriophages. These viruses can kill specific bacterial targets, leaving other cells unharmed. Additionally, their ability to propagate to high concentrations at the site of infection reduces the need for continuous application [9,10]. A considerable proportion of bacteriophage-related research now focuses on their practical application for the treatment of diseases including respiratory, gastro-intestinal, wound and skin infections [11,12,13,14,15,16].
While phages can be applied to areas of infection in liquid form, this does not necessarily represent the most effective means of treatment, with the few controlled clinical trials that have been carried out yielding mixed results thus far [17,18,19]. Apart from the difficulty in applying a liquid preparation to a site of infection, adverse conditions brought about by the body’s natural physio-chemical environment as well as its immune response could present a considerable challenge to bacteriophage stability . There has therefore been increased attention towards the development of alternative phage formulations, with a view to improving both their efficiency of application as well as their long-term stability [21,22].
The incorporation of bacteriophages into therapeutic formulations typically involves encapsulating them within a stabilizing substance [23,24]. Through such an approach, various antimicrobial materials such as powders, semisolids and nanofibers can be produced, providing more options for effective delivery at the site of infection and, consequently, improved patient outcomes. To this end, encouraging in vitro and in vivo results have been reported for various encapsulated phage formulations including spray and freeze-dried powders, emulsions and liposomes [25,26,27,28].
A strategy that has received considerably less attention with respect to therapeutic formulations is immobilization. Here, phages are instead bound to substrate surfaces. Whilst more commonly applied to the incorporation of bacteriophages into pathogen biosensors, immobilization represents a broad array of techniques which could potentially also be applied in this area. These are discussed in detail in this review, in addition to an overview of the formulation approaches carried out with respect to phage therapeutics thus far.
Examples of the various encapsulation approaches that have been carried out with bacteriophages.
|Encapsulation Method||Bacteriophage (Host Genus)||Formulation||Observations||Reference|
|Emulsification||K (Staphylococcus)||Semi-solid||Up to 10 days of activity at 20 °C|||
|Freeze-Drying||M13 (Escherichia)||Powder||<1 log drop in titer after 2 months at ambient temperature|||
|Spray-Drying||PEV2, PEV40 (Pseudomonas)||Powder||<1 log drop in titer after 1 year at 20 °C|||
|Liposome Entrapment||KP01K2 (Klebsiella)||Liquid||Up to 14 days of activity in vivo|||
|Electrospinning||Felix O1 (Salmonella)||Nanofibers||Phage activity of equivalent to 105–106 PFU/mL after fiber preparation|||
Summary of the benefits and limitations associated with the mass production of encapsulated therapeutic phage formulations.
|Emulsification||Material produced ideal for cream-type treatments|
Promote absorption when applied topically
|Difficult to transport/store at large scale|
Prone to bacterial contamination
Only stable when refrigerated
|Freeze-Drying||Final product easy to store/transport|
High stability post-production
Variety of applications
|Time-consuming, costly process|
Ice crystal formation can decrease phage viability
|Spray-Drying||Final product easy to store/transport|
High stability post-production
Variety of applications
Temperature can decrease phage viability during process
|Liposome Entrapment||Protection of phages against in vivo conditions|
Extensive studies demonstrating therapeutic effect compared free phage
|Encapsulation yield of phages in liposomes difficult to control|
Difficult to transport/store at large scaleOnly stable when refrigerated
|Electrospinning||Diverse array of materials can be produced.|
Easy deposition of fiber-encapsulated phage onto other substrates
|Fiber-spinning process can damage phages|
reference link :https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC8069877/
More information: Anaïs Eskenazi et al, Combination of pre-adapted bacteriophage therapy and antibiotics for treatment of fracture-related infection due to pandrug-resistant Klebsiella pneumoniae, Nature Communications (2022). DOI: 10.1038/s41467-021-27656-z