肠炎沙门菌噬菌体vB_SalP_QS的生物学特性及治疗小鼠沙门菌肠道感染的研究OA北大核心CSTPCD

In order to study the phage therapy methods for drug-resistant Salmonella,a virulent bacteriophage was isolated from sewage with Salmonella SE-21 as the host bacterium and named vB_SalP_QS.On the baisis of identifying the biological characteristics of vB_SalP_QS,vB_SalP_QSand vB_SalP_SE29 hybrid phage for the treatment of enteritis in mice caused by SE-21 was evaluated.The results showed that:1)The phage belonged to the order of caudoviruses(Caudovirales)by electron microscopy.The potency of the phage was 8×108 PFU/mL.2)Biological characterization showed that the phage vB_SalP_QS had an optimal multiplicity of infection(MOI)of 0.01,with an incubation period of about 40 min,and a lysis period of about 50 min.It had good activity at temperatures ranging from 4 ℃ to 60 ℃,and it was very stable within the range of pH 4-pH 10.vB_SalP_QS could lyse 17 strains of Salmonella by The plate spot test.The cracking rate was 44.7％.3)The phage vB_SalP_QS was 42 293 bp in total length,had a GC content of 49％,contained a total of 72 open reading frames(ORFs),and had no lysogeny,virulence factors,and integrase genes.4)In vivo therapeutic tests in mice showed that the minimum lethal dose of the host bacterium SE-21 was 5 × 108 CFU/mL,and the survival rate of infected mice treated with vB_SalP_QS(100 µL 1 × 107 PFU/mL)and vB_SalP_SE29(100 μL 1 × 107 PFU/mL)was 100％.The survival rate of mice in the vB_SalP_QS treatment group(200 µL 1×107 PFU/mL)was 80％.The survival rate of mice in the vB_SalP_SE29 treatment group(200 µL 1 × 107 PFU/mL)was 70％.All control mice died.5)Pathological observations showed that mixed phage could effectively kill Salmonella SE-21 and also better protect the intestinal villi of mice,which could significantly improve the survival rate of mice infected with SE-21.In conclusion,phage vB_SalP_QS has good acid-base,thermal stability as well as safety,and the therapeutic effect of mixed phage combination therapy is higher than that of phage monotherapy.This study provides an important experimental basis for the treatment of Salmonella infections with phage preparations and lays the foundation for the clinical application of mixed phage therapy.