| Pathogenic Escherichia coli is an important pathogen for pig breeding.Infection of newborn piglets may cause diseases such as yellow dysentery and white dysentery of piglets.Infected piglets may have diarrhea symptoms,affecting growth and development,leading to death in serious cases,and causing various direct and indirect economic losses.Due to the abuse of antibiotics and antibiotics,the drug resistance of pathogenic Escherichia coli is becoming increasingly serious,and the therapeutic effect of antibiotics and antibiotics is declining.It is necessary to seek solutions to this problem.Phage therapy,as a treatment scheme different from antibiotic therapy,has good research value in solving the problem of resistance of pathogenic Escherichia coli.In this experiment,Escherichia coli was isolated from piglet farms with yellow and white dysentery disease and fecal sewage samples were collected from the farm for phage isolation.The isolated phage was studied and its therapeutic effect on diarrhea caused by pathogenic Escherichia coli was verified through animal experiments,providing biological materials for the application of phage to solve the problem of decreasing therapeutic effect of antibiotic therapy.1.Isolation of porcine E.coli strainsFifty-eight strains of Escherichia coli were isolated and identified from yellow and white dysentery feces samples from pig plants in Wuhan and Yichang,Hubei Province.2.Study on the isolation,screening and biological characteristics of phage150 sewage samples were collected from the above pig farms for the isolation and purification of E.coli phage.A total of 32 E.coli phages were isolated.Using 58 strains of Escherichia coli as indicator bacteria,the lysate spectra of 32 phages were detected.Phage TPOW04(cleavage rate 71.67%)was selected for subsequent study based on the cleavage spectrum and fermentation conditions.Transmission electron microscopy of phages TPOW04 showed that TPOW04 belonged to the pnagus myococci family.The whole genome sequencing of phage TPOW04 showed that the total length of the phage genome was 359,183 bp,the GC content was 36%,and a total of 590 CDS were encoded.The whole genome did not contain drug resistance genes and virulence genes.The optimal infection complex number of phage TPOW04 was0.001.Good thermal stability,can tolerate 50℃.Phage activity remained stable in the range of p H4.0～10.0.3.Research on the application of phageThe therapeutic effect of phage TPOW04 on Escherichia coli diarrhea was studied in animal experiments.Sixty 3-week-old mice were randomly divided into 6groups: blank group,challenge no treatment group,antibiotic treatment group,phage group,phage treatment group and phage prevention group.The treatment group was challenged 24 h later,and the prevention group was challenged 2h after phage administration.After the experiment,the symptoms of mice in each group were observed,fecal scores of each group were calculated to calculate diarrhea,and the mice in each group were dissected to observe the lesions.The results showed that fecal score in the phage treatment group was significantly improved compared with that in the challenge without treatment group(P < 0.05),but there was no significant difference compared with antibiotic treatment effect(P > 0.05).There was no significant difference in fecal score between phage prevention group and blank group(P > 0.05).Statistically,the diarrhea rate of the phage treatment group was significantly reduced compared with the challenge no treatment group,and the cure rate and significant efficiency were similar to that of the antibiotic treatment group.Autopsy and lesion observation showed that there was no significant difference between the phage treatment group and the phage prevention group and the blank control group,and there was no obvious lesion in the challenge no treatment group.In conclusion,phage TPOW04 has good therapeutic and preventive effects on diarrhea in mice. |
