Isolation,Identification And Preliminary Application Of Enteroinvasive Escherichia Coli Phage DK-13

Enteroinvasive Escherichia coli(EIEC)is one of the pathogenic Escherichia coli,which mainly causes severe diarrhea in children and adults.EIEC does not produce enterotoxin.It mainly invades human colon epithelial cells,proliferates in the cell and extends to Adjacent epithelial cells have similar pathogenic mechanisms to Shigella.EIEC infections mostly occur in areas lacking or unable to obtain safe drinking water,sanitation services,or electricity.Ingestion of contaminated food or water may also cause infection.EIEC-induced epidemics have occurred all over the world,and most of them It is a developing country.Facing the abuse of antibiotics,the increasing number of multi-drug resistant bacteria,and the limitations of traditional food sterilization methods in the field of food safety,phage therapy is considered to be one of the possible solutions to the crisis related to bacterial antibiotic resistance.Prevention and treatment are increasingly accepted as a natural and green antibiotic intervention method and return to people's vision.In this paper,using EIEC as the host bacteria,a strain of potent phage DK-13 was isolated from the sewage collected from the First Hospital of Jilin University.The phage DK13 belongs to Caudovirales,Myoviridae,and T4 Tevenvirinae..The phage DK-13 presents a typical tadpole-like appearance,including an icosahedral head with a diameter of about 100nm and a retractable spiral symmetric tail;the phage DK-13 has strong host specificity and can only lysis the host bacteria EIEC;the optimal multiplicity of infection of phage DK-13 is 0.01;the incubation period of phage DK-13 is about 10 minutes,the lysis period is about 70 minutes,and the average burst is 164PFU/cell;phage DK-13 is at 50? and The activity is almost unchanged at around 60?,but it is easily inactivated in a high temperature environment above 70?.Under the condition of pH 5-10,the activity of phage DK-13 has no great influence.Under the condition of pH 4 or pH 11,The activity of phage decreased slightly,but when pH<4 or pH>11,phage DK-13 was almost inactivated.In this article,the whole genome of phage DK-13 was sequenced,and the sequencing results have been uploaded to GenBank,the sequence number is MT611523.The full length of phage DK-13 is 172275bp,the GC content is 40.18%,and it contains two tRNAs.No related virulence genes and drug resistance genes have been found in the genome of phage DK-13.There are 293 ORFs in the whole genome of phage DK-13,which are divided into six modules according to their functions:structural gene module,packaging gene module,nucleotide metabolism gene module,replication/recombination gene module,transcription/translation gene module and other functions;Evolutionary analysis showed that the gene arrangement results of phage DK-13 and the reported Escherichia coli phage vB_EcoM_VR20 are similar,and the two have a close relationship.The biofilm formed by bacteria is a medical hazard.It increases the bacteria's resistance to antibiotics and the host immune system,and is associated with persistent infections.EIEC can also spread food-borne diseases by contaminating food such as water,pork,milk,fruits and vegetables.In this paper,phage DK-13 is used to investigate whether it can effectively lyse or inhibit the formation of biofilms.The preliminary application of its bactericidal effect in pork and milk is carried out.The results show that phage DK-13 can effectively lyse and inhibit The formation of biofilm can effectively reduce the number of host bacteria in pork and milk.In summary,phage DK-13 has great potential in medical and food safety,and it can be considered for the development of phage therapy and phage preparations in the future.