Research – Disrupting the mixed species biofilm of Klebsiella pneumoniae B5055 and Pseudomonas aeruginosa PAO using bacteriophages alone or in combination with xylitol

Microbiology 

We investigated the potential of bacteriophages alone as well as in combination with xylitol for tackling mixed species biofilm of Pseudomonas aeruginosa and Klebsiella pneumoniae. When mixed species biofilm was established on polycarbonate discs, Pseudomonas aeruginosa formed the base layer which was physically shielded on the top by Klebsiella pneumoniae. Thereafter, mixed species biofilm was treated with bacteriophages. K. pneumoniae specific depolymerase producing phage KPO1K2, caused significant reduction in the count of Klebsiella. In contrast, P. aeruginosa specific non-depolymerase producing phage Pa29 failed to cause any reduction in the count of Pseudomonas. However, application of both the phages together resulted in significant reduction in the count of both the organisms. This observation suggests that depolymerase produced by phage KPO1K2, hydrolysed the top layer of K. pneumoniae and guided the entry of Pa29 to reach P. aeruginosa lying underneath. This phenomenon was confirmed when K. pneumoniae specific non-depolymerase producing phage NDP was used alongwith Pa29. Pa29 could not penetrate and reach its host bacterium. Xylitol worked synergistically along with phage resulting in significant decrease in counts of both the organisms. Disruption of mixed species biofilm by phage and xylitol was confirmed on the basis of amount of protein and DNA released. This phage based approach for altering the structural pattern and disrupting the mixed species biofilm is first of its kind. It can be used as topical application, coating for foreign devices or for aerosol delivery to tackle infections where both pathogens coexist in a biofilm mode.