Screening, identification and pathogenicity of phage-resistant strain of Salmonella

Abstract:

[Objective] To screen and identify resistant strains of Salmonella phage in the process of lysis, the differences of biological characteristics and the pathogenicity between resistant strains and the host strains were studied, to provide theoretical basis for solving the problem of presence of resistant bacteria in the phage therapy. [Methods] Salmonella phage-resistant bacteria were screened by secondary infection method and double-layer plate method. The differences between host strain ATCC 13076 and its phage-resistant strain R3 were compared by biological characteristics and virulence genes detection. The virulence of the bacteria was compared using mice challenge test and cell adhesion test. [Results] The growth curve of phage-resistant strain R3 was slightly slower than that of host strain; biochemical and virulent genetic tests showed that there was no difference between the resistant strain and host strain; compared to the host strain, the pathogenicity of the resistant strain to mice (Lethal Dose, 50%, LD₅₀) increased by 74.8% (P>0.05); and the adhesion ability to MODE-K cells were slightly weaker, but the difference was not significant. [Conclusion] Compared with the host strain, the biological characteristics and virulence genes of the bacteriophage-resistant strains did not change, and the pathogenicity of the strains was weakened in mice, but the adhesion ability to MODE-K cells was not significantly different.