Identification and functional insights into new phage tail-like bacteriocins targeting <i>Pseudomonas aeruginosa</i> as new antimicrobials

The current health crisis caused by multidrug-resistant (MDR) pathogens is one of the health problems of most concern globally. Infections caused by these pathogens, such as <i>Pseudomonas aeruginosa</i>, lead to high rates of complications, particularly in compromised patients such as cystic fibrosis (CF) patients. The need to counteract and minimize the forecast future impact has led to the rescue of phage therapy. The use of bacteriophages has important advantages, including highly specific targeting, self-amplification at the infection site, minimal disruption of the microbiome, safety, and biocompatibility. However, the capacity of bacteria to escape these entities results in a form of resistance that compromises the effectiveness of the therapy. This involves the search for potential alternatives, such as the phage tail-like bacteriocins (PTLBs), also named as tailocins. These high-molecular-weight particles resemble the tail structure of bacteriophages and are characterized by the absence of genetic material, avoiding the development of resistance, one of the major handicaps associated with phage therapy. In this study, we detected 34 different PTLBs in 75 <i>P. aeruginosa</i> genomes, with different serotypes and sequence types, 11 of which were characterized as novel F-type PTLB subtypes (F13-F24). Furthermore, we report that four selected PTLBs (R1, F15, F19, and R3-F24) can deal with bacterial infection, with the R1 and the F15 PTLBs being the most efficient in clearing infection <i>in vitro</i>, yielding a survival rate of more than 75% in the <i>Galleria mellonella</i> larvae <i>in vivo</i> model. This reaffirms the potential of PTLBs to control <i>P. aeruginosa</i> infections, which can cause chronic infections in some patients, such as people with CF, due to its strong impact as a MDR bacterium.IMPORTANCEThe 75 <i>Pseudomonas aeruginosa</i> genomes from people with cystic fibrosis in the study collection included at least one phage tail-like bacteriocins (PTLB) cluster. From the 34 different PTLBs detected in the study collection, 7 were R-type, 10 were complex (R- and F-type encoded), and 14 were F-type PTLBs. Eleven new F-type PTLBs were described in the <i>P. aeruginosa</i> collection under study. An association between the O-antigen present on the surface of the <i>P. aeruginosa</i> isolate and the encoded PTLB subtype was detected. The R1 and F15 PTLB subtypes display high antimicrobial activity both <i>in vitro</i> and <i>in vivo</i> (<i>Galleria mellonella</i>).