Pseudomonas aeruginosa bacteriophage PA1Ø requires type IV pili for infection and shows broad bactericidal and biofilm removal activities

Abstract

We isolated a new lytic Pseudomonas aeruginosa phage that requires type IV pili for infection. PA1Ø has a broad bactericidal spectrum, covering Gram-positive and Gram-negative bacteria, and can eradicate biofilm cells. PA1Ø may be developed as a therapeutic agent for biofilm-related mixed infections with P. aeruginosa and Staphylococcus aureus.

Fig 1

Three pilus mutants grow normally in the presence of PA1Ø. The growth of three pilus-negative strains and wild-type PAO1 was monitored by measuring the optical density (OD) at 600 nm. PAO1 growth in plain LB is included as a control. *, P < 0.001 versus all other growth.

Fig 2

Bactericidal and biofilm removal effects of PA1Ø. Planktonic cultures (A) and 1-day-old biofilms (B) of eight different bacterial species were treated with PA1Ø at an MOI of 200 for 6 h and 1 × 10¹⁰ PFU of PA1Ø for 3 h, respectively. Triphenyltetrazolium chloride (TTC) absorbance values at 600 nm were compared with those of non-PA1Ø-treated controls (gray bars). 1, S. aureus ATCC 25923; 2, S. aureus WS-05; 3, S. aureus D43-a; 4, S. epidermidis KNUH-134; 5, S. epidermidis KNUH-174; 6, S. hominis KNUH-328; 7, S. hominis KNUH-329; and 8, P. aeruginosa PAO1. Experiments were performed three times independently, and values are means and standard deviations.

Fig 3

Biofilm removal capacity of PA1Ø. Non-PA1Ø-treated (A, C, E, and G) and treated (B, D, F, and G) biofilms of four bacterial strains were visualized by scanning electron microscopy. (A and B) P. aeruginosa PAO1; (C and D) S. aureus ATCC 25923; (E and F) S. epidermidis KNUH-134; (G and H) S. hominis KNUH-329.

Fig 4

Alignment of the PA1Ø and D3112 genomes. This MAUVE-generated diagram shows the degree of sequence similarity between two phages. Both gene maps are measured against a ruler in base pairs. The degree of sequence similarity between two genomes is indicated by the height of the similarity peaks. The six genomic dissimilarity regions are marked with black bold lines and numbered, and affected genes in both phages are listed in numbered boxes. Regions A to C show highly conserved regions of PA1Ø and phage D3112.