Abstract:

Objective To identify efficient and broad-spectrum phages aiming at multi-drug resistant Pseudomonas aeruginosa. Methods Clinical isolated P.aeruginosa strains were used as host bacteria. The P.aeruginosa phages were isolated and purified from sewage. The shape and size of phages were observed by transmission electron microscope (TEM) after phosphorus acid negative staining. Titer, host range, pH stability, and thermal stability were detected. One-step growth curve, adsorption curve, and infection curve were plotted. The DNA of phages was extracted for sequencing and analysis. Results One strain of P.aeruginosa phage was isolated and named D204. The activity of D204 was high at temperatures from 37 to 50 ℃ and pH values from 4 to 11. TEM observation showed that the phage consisted of a polyhedron head with the diameter of 50 nm and a 15 nm long tail. One step growth curve indicated that during the lysis of host bacteria, the latent period of phages was about 30 min, outbreak period was about 40 min, and the burst size was about 160 pfu/cell. The adsorption curve showed that the adsorption rate was more than 95% within 50 min. The infection curve indicated that the growth of host bacteria was inhibited when the multiplicities of infection were 0.1 and 1. The growth of host bacteria was totally inhibited after 180 min. The genome of phages was circular double-stranded DNA with total length of 50 609 bp and the content of GC was 44.8%. It was predicted that there were 75 open reading frames in the genome. Conclusion Isolated P.aeruginosa phages D204 have a strong lytic ability and wide ranges of thermal and pH stability and can serve as reserved phages of P.aeruginosa.

Key words: Pseudomonas aeruginosa, phages, genome, biological characteristic