Biofilm Prevention and Removal in Non-Target Pseudomonas Strain by Siphovirus-like Coliphage

<b>Background/Objectives.</b> Bacteriophages have gained significant interest as a potential solution to combat harmful bacteria, especially in the fight against antimicrobial resistance. With the rise in drug-resistant microorganisms, the medical community is increasingly exploring new alternatives to traditional antibiotics, and bacteriophages offer several advantages in this regard. However, phage applications still face some challenges, such as host specificity. <b>Methods.</b> In this study, a somatic <i>Siphovirus</i>-like coliphage (SOM7) was tested for inhibiting the biofilm-forming capacity of the non-target strain <i>Pseudomonas aeruginosa</i> (ATTC 10145). The phage-sensitive strain <i>E. coli</i> WG5 was used as a control. The selected microorganisms were first tested for growth in the presence of SOM7 at three different concentrations (10⁵, 10⁷, and 10⁹ PFU/mL). <b>Results.</b> As expected, the phage-sensitive <i>E. coli</i> WG5 was fully inhibited by the coliphage, and no phage-related affection on the growth rate was observed for the SOM7-resistant <i>P. aeruginosa</i>. More notably, increasing concentrations of SOM7 significantly reduced both the biofilm-forming capacity and the amount of pre-established bacterial biofilm of the phage-insensitive <i>P. aeruginosa</i> (24.9% and 38.8% reduction in the biofilm-forming ability, and 18.8% and 28.0% biofilm degradation for 10⁷ PFU/mL and 10⁹ PFU/mL SOM7, respectively; <i>p</i> < 0.05). These results were supported by transmission electron microscopy (TEM) imaging, providing unprecedent evidence for the interaction of the somatic coliphage with the non-host strain. <b>Conclusions.</b> Although more studies in other biofilm models are necessary, our results show for the very first time that bacteriophages could potentially be used as an alternative to achieve desired anti-biofilm and biofilm-degrading activity in non-host bacterial strains.