**5. Phage therapy**

A bacteriophage therapy is a treatment for a patient's bacterial disease illness that is provided after the patient has been diagnosed. Bacteriophages are the most valuable and ubiquitous (1031) organisms in the world, and are known to infect >140 bacterial genera. Description of phages and their antibacterial activity has initially been set up [6]. Bacteriophage therapy exhibits precise antibacterial lytic activities that have turned out to be a really useful concept to kill even an intracellular pathogenic bacterium and guarantee future development and consequently the therapeutic phages are re-emerging. As a substitute to antibiotics, experimental bacteriophage therapy might replace them when they fail to treat chronic infections, and such successful eradication of drug-resistant bacteria has been properly identified and demonstrated [65–72]. A single dose of phage has been shown to be more effective treatment than many doses of antibiotics such as amphetamines, tetracycline but chloramphenicol [73]. Moreover, careful phage collection, propagation, and purification requires complete experimental conditions. Such a focus ought to assist in the improvement of medical phage therapy utilized to a variety of systems, which is viewed an attribute on an emerging choice to antibiotic therapy and vaccination. The consequences of phage therapy are dependent on the plan of preparations and rout of administration of bacteriophage. The best possible administration route for phage preparations which should facilitate sufficient phages coming into direct contact with the bacteria. Routes of phage administration vary from oral, intravenous to multiple topical applications. There are different types of bacteriophage preparations developed to facilitate direct contact of the phage with the pathogenic bacterium for special bacterial infections and they are: (i) a phage powder, phage-containing lotion or dry gauze layer containing phages could be used for skin infections [74]. (ii) bacteriophages that have been sprayed dry become phages that can be inhaled as powder [75–77]. (iii) aerosolized phage preparations may be chosen for respiratory tract infections [76–78]. (iv) cream of phage

preparations for skin infections. (v) injectable types of phage formulations [41, 47, 79]. (vi) phage infusion preparations may be considered for bloodstream infection [80, 81]. (vii) capsules containing phages (encapsulation/micro-encapsulation) that can protect particles from stomach acid inactivation should be preferred for gastrointestinal infections [75, 82]. An improved understanding of how synergic interactions of bacteriophages, cocktails with antibiotics impact bacterial infection is needed to stop unintentional inhibition of phage replication. Aerophages and IV phages each rescued 50% of animals from severe MRSA pneumonia. A mixture of aerophages and IV phages rescued 91% of animals, which was higher than either monotherapy or cocktail phage therapy [12]. Phage alone or a mixture of phages with antibiotics were treated against several bacterial infections in skin, blood, lung, and chronic otitis [36, 66, 80]. In contrast, other clinical reports have shown that some phages do not work due to constant infection and ETEC (Enterotoxic *Escherichia coli*) -complex diarrhoea [42, 83]. However, the prevalence of MDR bacteria is increasing, and our port drug portfolio is obsolete. The evolution of antibiotic resistance bacteria has thus become a major world health care problem. Clinical threats include MRSA, *Mycobacterium tuberculosis* and Vancomycin-Resistant *Enterococcus* (VRE) [84–86]. MDR bacterial infection is challenging and expensive to treat because of the increased resistance to all the antibiotics in practice. According to the Centres for Disease Control and Prevention (CDC), two million people are infected with antibiotic-resistant bacteria, and 23,000 people die each year in the USA from antibiotic-resistant bacterial infections. Prescribing antibiotics for the treatment of only standardized bacterial infections may slow down the process, but will not slow down the overall trend. Frequent use of antibiotics against diseases in humans and other organisms contaminates the environment and its cumulative effect on the development of antibiotic-resistant bacteria. As the number of antibiotic-resistant bacteria increases, alternative methods must be developed to effectively control them. Therefore, the use of antibiotics is a danger. Bacteriophage therapy with specific phages or a cocktail of phages signify an exciting alternative development to antibiotic therapy and vaccination. The progress of bacteriophage assays, biosensor tools, and bio-nano-targeted drug delivery system against drug-resistant bacteria elucidated. Bасteriорhаges are highly specific to target bасteriа, and hence its usage is targeted toward а specific bасteriаl species and signifiсаntly minimizes off-targets effects on microbiome or human patient, as bасteriорhаges do not directly аffeсt human cells [87]. Thus, phage treatment has been re-emphasized as the severity of drug-resistant bacteria has increased [66]. Therapeutic bacteriophages, units and outcome of the treatment of some antibiotic resistant bacterial infections are presented in **Tables 1** and **2**.

### **5.1 Personalized therapeutic phage**

The term "personalised phage therapy" refers to the preparation and precise targeting of phage(s) against bacteria isolated from infected patients. Phage therapy has made extensive use of such a precise approach [80, 96], (**Table 3**). The patient's conditions need to be observed regularly to evaluate whether or not they are improving, and clinical samples from bacterial infection sites should be assessed in a timely manner to evaluate therapeutic efficacy, the emergence of phage-resistant strains and efficient phage titers. Phage should be replaced once a particular phageresistant bacterium emerges [96]. If there are no phage in the library that kill a phage-resistant bacterial strain, the bacterial strain can be further used as a host bacterium to screen various types of samples (e.g., soils, faeces, urine) to isolate new effective phage. Such new bacteriophages can be added continuously to enrich the phage library if they meet the criteria. Phage therapy can be considered as an




**Table 2.**

*Efficacy of therapeutic bacteriophages treatment of antibiotic resistant bacterial infections.*

example of personalized medicine for bacterial infections [80]. Phage resistance may also be accompanied by changes in antibiotic resistance [99]. Therefore, the antibiotic resistance profile of phage-resistant strains should be simultaneously tested. The synergistic bactericidal activity of combining phage and antibiotics in the clinical cases should be considered [100] and further treatment strategies using phage alone and/or in combination with antibacterial drugs should be considered based on the results. The development of phage-sensitive and -resistant strains should be monitored regularly during phage therapy to see if phage therapy is a viable choice for successfully dealing with this issue. A clinical trial demonstrating the therapy's beneficial effects is critical in verifying its medical importance.

### **5.2 Gangrene wounds**

Gangrene is the death of body tissue due to bacterial infection or lack of blood flow. Gas gangrene is caused by infection with a bacterium called *Clostridium perfringens* which in turn produces toxins that release gas causing tissue death [91]. A concoction of bacteriophages has been used to cure gangrene which is lively towards *Staphylococcus* spp., *Streptococcus* spp. and *Clostridium* [36, 50, 56]. Therapeutic efficacy of the phage has been improved, with the utility of "Pyophage" (a poly-specific cocktail of phage), achieved after detection of the particular etiologic agents and application of mono-specific lytic phage. The sequence of phage therapy treatments consisted of washings of the wound with a phage preparation, followed by subcutaneous injections of phage(s) as soon as to 4 instances per day. The utility of phage therapy has led to the removal of 69% Staphylococcal and 50% Streptococcal infections. Poly-specific (Pyophage, Sekstaphage) and mono-specific therapeutic phage cocktails developed have been used. Bacteriophages had been administered locally, via subcutaneous injections, and orally. Notably, phage therapy used to be carried out as a monotherapy, or complex treatment, which covered phage(s) and antibiotics administration. The investigations revealed that complicated treatment diminished the healing time by way of 1.2–2.5 times compared with antibiotic treatment. Even application of bacteriophages unique to one of the infectious agents in a wound expanded restoration and prompted quicker recuperation and purification. Importantly, it has been proved that a single utility of a bacteriophage would now not be adequate to stop infectious lesion problems. However, the investigators could not be concluding that the utility of bacteriophages barring antibiotics is better, as they had been unsuccessfully handled with antibiotics. They cautioned that the use of phage preparations supplied a fantastic impact on mono-infection, whilst complicated treatment, consisting of bacteriophages and


### **Table 3.**

*Therapeutic bacteriophages for personalized treatments.*

antibiotics, was once required for combined bacterial infections [101]. The use of distinctive bacteriophages was once greater than therapy with unique poly cocktails [102]. The most effective of this kind of custom-made phage therapy can be accelerated by using the specificity and virulence of phage to host strains. However, modified phage preparations require certain planning due to the fact they can incorporate temperate bacteriophages produced with the aid of a kind of scientific bacterium which has been used for adaptation.

### **5.3 Burn wounds**

Burn wounds of patients have risks of bacterial infections. The floor of burn wound areas of sufferers may exhibit sepsis, lymphopenia, and intoxication. The


### **Table 4.**

*Therapeutic bacteriophages for antibiotic-resistant burn infections.*

**Figure 5.** *Diabetic chronic non-healing wounds (NHW).*

use of phage therapy was shown to be superb in eradication of pneumonia, the drug-resistant (MDR) *P. aeruginosa* infections in the burn wounds, and stopping the formation of sepsis [92, 103–107]. Therapeutic bacteriophages used for treatment of antibiotic-resistant burn infections are detailed in **Table 4**. In a complicated remedy comprising bacteriophages per OS and antibiotics, the use of bacteriophages has proven higher medical consequence in sufferers with contaminated burns (29% complicated instances of wounds) than in sufferers dealt with antibiotics (12.6% of cases) [103]. The volume of therapeutic phage particles (≥10<sup>6</sup> PFU/ml) used in the remedy is proven to be very extensive and the high-quality result of cure varied relying on the phage titer, routes of phage administration, sensitivity, specificity, and accessibility of bacterial host to the phage, length of phage therapy progression. A single dose (10<sup>3</sup> PFU/ml) of the phage BS24 has been confirmed to provide a

wonderful impact and in contrast, no encouraging wound restoration response has been determined when the phage cocktail BFC-1 10<sup>9</sup> PFU/ml has been utilized at the wound floor [51, 92, 106, 109]. Dosage, remedy procedure, safety, efficacy, and pharmacodynamics of two phage cocktails, suggestions to deal with *E. coli*, and *P. aeruginosa* contaminated burn wounds are described [51].
