Abstract
We here describe two novel lytic phages, KT28 and KTN6, infecting Pseudomonas aeruginosa, isolated from a sewage sample from an irrigated field near Wroclaw, in Poland. Both viruses show characteristic features of Pbunalikevirus genus within the Myoviridae family with respect to shape and size of head/tail, as well as LPS host receptor recognition. Genome analysis confirmed the similarity to other PB1-related phages, ranging between 48 and 96%. Pseudomonas phage KT28 has a genome size of 66,381 bp and KTN6 of 65,994 bp. The latent period, burst size, stability and host range was determined for both viruses under standard laboratory conditions. Biofilm eradication efficacy was tested on peg-lid plate assay and PET membrane surface. Significant reduction of colony forming units was observed (70-90%) in 24 h to 72 h old Pseudomonas aeruginosa PAO1 biofilm cultures for both phages. Furthermore, a pyocyanin and pyoverdin reduction tests reveal that tested phages lowers the amount of both secreted dyes in 48-72 h old biofilms. Diffusion and goniometry experiments revealed the increase of diffusion rate through the biofilm matrix after phage application. These characteristics indicate these phages could be used to prevent Pseudomonas aeruginosa infections and biofilm formation. It was also shown, that PB1-related phage treatment of biofilm caused the emergence of stable phage-resistant mutants growing as small colony variants.
Highlights
The aerobic gram-negative bacterium Pseudomonas aeruginosa is an opportunistic human pathogen, that causes chronic and acute infections of burn wounds, respiratory and urinary tracts [1]
The bacteriophages were examined by transmission electron microscopy (TEM) and classified on the basis of their morphological features to Pbunalikevirus (Fig 1)
The KT28, with a larger genome encapsulated in a bigger virion, exhibits the same latent period, but much lower burst size in comparison to KTN6 phage (64 ± 0.98 pfu/cell versus 96 ± 0.2 pfu/cell)
Summary
The aerobic gram-negative bacterium Pseudomonas aeruginosa is an opportunistic human pathogen, that causes chronic and acute infections of burn wounds, respiratory and urinary tracts [1]. P. aeruginosa is the major cause of morbidity and mortality in individuals suffering from cystic fibrosis [3] This bacterium possesses a wide array of virulence factors that do cause extensive tissue damage, and directly interfere with the human immune system [4]. P. aeruginosa reversibly regulates gene expression and changes its phenotype and genotype in response to the environmental signals during the infection [6]. This provides a protective mode that allows microorganisms to survive in hostile environments and disperse seeding cells to colonize new niches with desirable conditions [7]
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