The aim of this study is to evaluate the in vitro and in vivo antibacterial potential of Ly-sZHSHW,a phage lysin against Acinetobacter baumannii infections,and to study its characteris-tics.The pET28a-Lys recombinant plasmid containing LysZHSHW coding gene was constructed by PCR,enzyme digestion and ligation using the expression plasmid pET28a as the backbone and ex-pressed in E.coli BL21(DE3).After confirming the expression of the LysZHSHW through West-ern blot analysis,its characterization and potential applications were assessed both in vitro and in vivo.The results showed that the pET28a-Lys recombinant plasmid was successfully constructed and the LysZHSHW protein was expressed correctly.The mass concentration of the purified en-zyme was 4 086 mg/L,which could be used for subsequent experiments.The enzymatic activity of LysZHSHW was determined to be 630 U/μg,with maximum activity observed at 25 ℃ and pH9.0.In vitro experiments demonstrated that 1 000 or 750 mg/L of LysZHSHW,in the presence of EDTA,resulted in a four-log reduction in bacterial counts without any cytotoxicity.In vivo,2.5 μg of LysZHSHW combined with EDTA could increase the survival rate of Galleria mellonel-la larvae infection model to 92.86％after 24 hours,and 0.15 mg of LysZHSHW reduced the bacte-rial load in the thighs of mice by 2.8 logs and alleviated the inflammatory response in muscle fi-bers.In conclusion,LysZHSHW derived from Acinetobacter baumannii bacteriophage exhibited characteristics such as stability at room temperature,alkaline pH,and safety,making it a promis-ing candidate as a novel antimicrobial agent.
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