## 4 The Use of Mycobacteriophages in Diagnostics and Therapy  
The escalating problem of antimicrobial resistance arises from a complex interplay between the intrinsic adaptability of microorganisms and anthropogenic factors. Bacteria have evolved a variety of mechanisms to withstand antimicrobial agents, including efflux pumps, enzymatic degradation, target modification, biofilm formation, and metabolic dormancy. These innate strategies are further amplified by environmental pressures, most notably the widespread and often indiscriminate use of antibiotics in human medicine, veterinary practice, agriculture, and aquaculture. Selective pressure from subtherapeutic or inappropriate antibiotic use, such as incomplete courses of treatment or the prophylactic use in livestock, accelerates the emergence and dissemination of resistant strains. Horizontal gene transfer facilitates the rapid spread of resistance determinants within and across bacterial species, compounding the problem. The resulting proliferation of multidrug-resistant and extensively drug-resistant organisms, including _M. tuberculosis_, poses a critical challenge to global health. Concurrently, a stagnation in the development of new antibiotic classes has led to growing dependence on older, less effective treatments [27]. This imbalance between resistance evolution and therapeutic innovation underscores the urgent need for alternative antimicrobial strategies. Among emerging alternatives, phage therapy has gained renewed attention as a targeted and potentially effective approach to combat drug-resistant infections, including those caused by _M. tuberculosis_. Unlike antibiotics, bacteriophages offer high specificity for their bacterial hosts and can evolve alongside them, potentially limiting the long-term impact of resistance. Nevertheless, phage therapy is not without limitations. Issues such as a narrow host range, potential for immune neutralization, regulatory hurdles, and the need for individualized matching between phages and pathogens present significant challenges to widespread clinical implementation. Phage therapy involves the administration of bacteriophages through various routes, depending on the infection site. These include intravenous, oral, topical (e.g., wound dressings), intrattissue, rectal, or parenteral delivery methods [71]. To provide a clearer perspective on its clinical potential, the key advantages and disadvantages of phage therapy are summarized in Figure 2.  
In polymicrobial infections, phage cocktails--mixtures of different phages--are often used to enhance therapeutic efficacy [74]. These cocktails can be delivered in liquid or aerosol form, particularly in treating burn wound infections caused by pathogens like _Pseudomonas aeruginosa_ or _Staphylococcus aureus_[79]. Recently, combination therapy involving antibiotics and phages has shown promise in reducing the likelihood of bacteria developing a resistance [80]. Phage therapy is also cost-effective and, to date, has shown a  
Figure 2: Advantages and disadvantages of phage therapy. Phages selectively destroy pathogenic bacteria without disturbing the natural microbiota and are safe for human cells. They replicate at the infection site and are naturally excreted and can cross the blood–brain barrier. However, phage therapy requires prior identification of the pathogen, may be ineffective in mixed infections, can trigger immune responses, and potentially transfer toxin genes between bacteria. Based on Refs. [72; 73; 74; 75; 76; 77; 78]. favorable safety profile in humans. In addition to therapeutic use, phage solutions are used for disinfection purposes, including the decontamination of surgical tools and hospital surfaces [81]. Despite their ability to lyse pathogenic bacteria, phages lost popularity in Western Europe following the advent of antibiotics. Early phage studies were often poorly understood and yielded inconsistent results, which led many researchers to abandon this line of investigation [78; 82].