## 5 New Technologies to Support the Development of Phage Therapy
CF affects the function of several organs, including the lungs, that predispose patients to develop chronic, recurrent, multispecies, biofilm-associated bacterial pulmonary infections, most commonly caused by drug-resistant _P. aeruginosa_, _S. aureus_, and _Bulloldiericepacia_ complex strains. Chronic inflammation, pulmonary tissue damage, and progressive respiratory insufficiency heavilylimit the quality of life and finally cause the premature death of CF patients [124; 125; 126; 127]. A summary of the case report of phage therapy in a 26-year-old man with CF described by [PERSON] et al. [124] is presented in Table 2.  
However, there is limited progress in applying phage therapy against _M. tuberculosis_ infections, and the few in vivo studies described so far have involved only animal models (Table 2). First of all, anti-_M. tuberculosis_ activity tested in vitro is not common among mycobacteria phages and appears to be restricted mainly to cluster K, G, and sub-clusters A2 and A3, including the studied TM4, L5, and D29 mycobacteria phages [118; 119]. Fortunately, the number of mycobacteria phages being discovered constantly increases, and they frequently expand or switch the host range. [PERSON] et al., analyzing the genomes and predicting the host ranges of P mycobacteria phages, found that subcluster P1 phages are mostly limited to _Mycobacterium_ spp., infecting mainly _M. abscessus, M. marinum_, and _M. smgematis_, but also _M. fortuitum, M. gilvum_, and _M. intracellular_. Meanwhile, subclusters P2-P6 may infect additional bacterial genera, including _Gordonia, Rhizobium, Corynebacterium, Clostridides_, and _Clostridium_. Most cluster P phages have a conserved integration-dependent immunity system, involving integrase (Int), repressor (Rep), and Cro proteins, which controls the switch between lytic and lysogenic cycles and probably also determines host range. So, genetic switch complexity may influence host range evolution [129]. Although the temperate nature of most P phages limits their use in bacteriophage therapy, these observations bring hope for the development of genetic engineering to alter mycobacteria phages specificity and enhance their effectiveness. [PERSON] et al. used a temperate _L. monocytogenes_ phage PSA, with a very narrow host range restricted to serovar 4b _Listeria_, as a model for host range re-programming based on receptor binding protein (RBP) modifications [130]. \begin{table}
\begin{tabular}{p{14.2 pt} p{142.3 pt} p{142.3 pt} p{142.3 pt} p{142.3 pt} p{142.3 pt}} \hline \hline
**Model** & **Target** & **Infection** & **Phase** & **Therapy Mode** & **Effects** & **Reference** \\ \hline Human (CF patient, genotype H11997/2184 insA) & _M. abscessus_ & _M. abscessus_ & _BPs_A33 HTH_HIRM10 (H1997/2184 insA) & & Clinical improvements: (a host range mutant of engineered lytic phage BPs with the depleted part of the repressor gene); (b) & & \\  & & &  
They identified Gp15 as the PSA RBP, showed its crystal structure, and, combining synthetic biology with structure-guided approaches, prepared PSA mutants containing chimeric RBPs that exhibited reprogrammed host specificity and changed plating efficiency [130]. Mycobacteriophages are a promising alternative to antibiotics and chemotherapeutics to treat the infections caused by _Mycobacterium_ spp. However, their use in treating TB still seems to be a long way off. Of course, some unfavorable phenomena impacting treatment efficacy, such as bacterial resistance to phages or different susceptibility patterns resulting from bacterial morphotypes, should also be considered. Bacterial resistance to phages usually arises through mutations affecting the bacterial surface or internal components that interfere with the phage adsorption or lifecycle. However, mutants that totally disrupt phage adsorption have yet to be isolated among Mycobacterium strains [121]. Meanwhile, different susceptibility happens and may be a consequence of the mycobacterial morphotype. [PERSON] et al. have demonstrated that smooth strains of _M.