Isolation,Identification And Genome Analysis Of Escherichia Coli NMGCF-19 Strain Associated With Lamb Meningoencephalitis

Escherichia coli(E.coli)is an opportunistic pathogen that can cause diarrhea,dehydration,urethritis,bacteremia,sepsis,pneumonia,meningoencephalitis and other diseases in humans and livestock and poultry.It can be divided into enteric pathogenic and non-enteric pathogenic E.coli.Due to E.coli has tens of thousands of serotypes and the cross-protection between different serotypes is poor,Colibacillosis,becomes more difficult to prevent and treat.Currently,colibacillosis is still one of the important infectious diseases that pose severe threat to the development of domestic animal husbandry.Since the different serotypes can be easily found in different regions,even in the same farms,therefore,the isolation and identification of strains and the analysis of their virulence and resistance genes are of great significance for exploring the prevention and treatment strategies of the disease.In this study,we investigated an outbreak of disease characterized by severe diarrhea and neurological symptoms on a sheep farm in the Chifeng of Inner Mongolia.Isolation and characterization of the potential pathogens identified the Escherichia coli as the causative agents for the outbreak via bacteria isolation,morphological observation,biochemical characterization,and sequencing.The identified bacterium strain was designated as NMGCF-19 strain.Characterization of this bacteria revealed its median lethal dose to be 1.0×10~6 cfu.The pathogenicity was also determined using ICR mouse model.The results showed that the NMGCF-19strain was a pathogenic E.coli with a capability of causing the bacteremia and broad pathological lesions in mice.Moreover,the NMGCF-19 strain was also detected in the brain tissues,suggesting it has the ability of disrupting the blood brain barrier.Further investigation demonstrated that the expression of tight junction protein in mouse brain tissue decreased and the expression of inflammatory cytokines increased by q PCR and Western blot methods,thus indicating that the NMGCF-19 strain may invade brain tissue and cause meningitis by destroying the blood-brain barrier.This study determined and analyzed the complete genome sequence of the NMGCF-19 strain.After sequencing,a total of 1,189,209,800 bp Clean Data,27186bp repetitive sequences,and 5040 codes were obtained.Further analysis showed that756 were identified as potential genes for bacterial adhesion,flagella synthesis,movement,fimbriae synthesis,toxins,and invasion.The findings of virulent-related factors and 46 resistance genes,as such hemolysin,are very important for drug target screening and vaccine development for colibacillosis.In summary,a strain of pathogenic Escherichia coli was isolated and identified,which can cross the blood-brain barrier and cause meningitis in lambs,and identified potential virulence,resistance and other functional genes in the strain.The above results provide a theoretical basis and preliminary basis for the diagnosis,treatment and vaccine development of colibacillosis in this area.