Isolation,Identification and Biological Characterization Analysis of Phage BP32 from Multidrug-Resistant Escherichia coli
[Objective]The aim of this study was to isolate a phages that specifically lysed multidrug-resistant Escherichia coli and clarify the biological properties and genomic characteristics of the isolated phages furtherly.[Method]In this study,Escherichia coli was isolated from the lung tissue of dead goats and its drug resistance was analyzed by drug sensitivity test.Using Escherichia coli ER2738 as host bacteria,the phage was initially propagated from farm sewage,and the host spectrum of the phage was determined by drop method.The phage of lytic Escherichia coli was isolated and purified by double agar plate method,and its morphology,optimal multiplicity of infection(MOI),growth curve,pH and temperature tolerance were further studied.Finally,the whole genome sequence was determined by high-throughput sequencing platform,and the characteristics of the genome and genetic evolution were analyzed.[Result]A multidrug-resistant Escherichia coli strain named YNEC001 was isolated from the lung of dead goats.A phage(BP32)that could specifically lyse YNEC001 strain was isolated.Electron microscopic observation showed that phage BP32 belonged to Myoviridae,with the optimal MOI of 0.1,the incubation period was about 30 min,and the lysis period lasted about 60 min,and the average amount of lysis was about 660 PFU/cell.Phage BP32 could maintain stable activity at 30-50 ℃ and pH 4.0-10.0.The genome length of phage BP32 was 166 346 bp,the GC content was low(35.42％),no drug resistance genes and virulence factors were found,and the genome contained 261 open reading frame(ORF),of which 125 were known functional genes and contained 8 tRNA.At the genome-wide level,the nucleotide similarity between phage BP32 and enterobacter phage Escherichia BF15(MW822007)was the highest(98.25％).Based on the phylogenetic analysis of the large subunit of the terminal enzyme,BP32 was most closely related to Escherichia vB_EcoM_SP1(MT682709),but more distant to Escherichia BF15(MW822007).[Conclusion]In this study,a strain of multidrug-resistant Escherichia coli YNEC001 was isolated,and phage BP32,which could specifically lyse the YNEC001 strain,was isolated.This phage had strong lytic ability and good stability,and had the potential to be developed as a therapeutic agent for multidrug-resistant Escherichia coli.
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