Isolation,identification And Biological Characteristics Of Pathogenic Escherichia Coli Phage From Dolphin

Enterotoxigenic Escherichia coil(ETEC)is one of the main pathogenic bacteria causing diarrhea in animals,which poses a serious threat to dolphin breeding industry.Once infected with bacterial diseases,it is easy to cause a wide range of infection,resulting in the morbidity and even death of Marine mammals,resulting in huge economic losses.ETEC can produce many kinds of enterotoxin,among which heat-resistant enterotoxin is the main pathogenic factor of dolphin diarrhea.At present,there are few prevention and control measures against the diseases of dolphins,and because of the particularity of dolphins,the sterilization of the aquaculture pond water can only rely on disinfectants.Therefore,bacteriophages,which are pollution-free and can replace antibiotics for the treatment of Marine mammal bacterial diseases,have gradually become a research hotspot.Therefore,aiming at the increasingly serious problem of bacterial resistance in the ocean,this study isolated a strain of Escherichia coli from the feces of diarrhea dolphins in an aquarium in Qingdao,Shandong Province.Through isolation culture,16 S r DNA identification and drug sensitivity detection,the bacterium was identified as multiple drug resistant and heat resistant enterotoxin Escherichia coli.With it as the host bacteria,a highly efficient lytic phage was screened and named Wilfred.Through studying its biological characteristics,whole genome sequencing and clinical experiment,it provides the basis for clinical application of E.coli phage.Results showed that the negative colonies of phage Wilfred were moist and clear with regular smooth edges.The optimum infection number was 1,the optimum temperature was 20-60℃,and the optimum p H was ph 6-9.Bioinformatics analysis showed that the total length of the genome fragment of phage Wilfred was 49802 bp,GC content was 51.95%,and there were 78 ORF reading frames.Among the proteins with known functions,they are mainly some phage head and tail proteins and DNA replication related proteins.Phylogenetic tree analysis showed that Lambda＿2H10was closely related to Escherichia virus.In clinical trials,phage Wilfred was used to treat E.coli infection in mice and Mary fish.In conclusion,bacteriophage Wilfred has a clear host and has the temperature and acid-base stability suitable for dolphin rearing ponds,which can lay a theoretical foundation for the effective prevention and control of heat-resistant enterotoxin-resistant E.coli infection in dolphin rearing.