Biological Characteristics of Salmonella pullorum Lytic Phage PC79-13 and Preliminary Detection of Its Fluorescently Labeled Host Bacteria
Objective:To establish a protocol for detecting Salmonella pullorum with fluorescently labeled bacteriophage PC79-13.Methods:A lytic bacteriophage specific for Salmonella pullorum(abbreviated as S.pullorum)was isolated from sewage.Its morphology was characterized by transmission electron microscopy(TEM).The infectivity of the bacteriophage was assessed by generating a one-step growth curve after liquid culture with the host organism.Additionally,its thermal stability,pH stability,UV stability,and optimal infectious dose were measured,and the bioinformatics methods were used to understand its biological characteristics and genetic features.Finally,the bacteriophage was labeled with FITC to generate a fluorescent probe to detect Salmonella pullorum.Results:The isolated bacteriophage PC79-13 formed uniform,clear plaques on double-layer agar plates containing S.pullorum C79-13.Electron microscopy showed that PC79-13 has an icosahedral head about 60 nm in diameter and a long tail,placing it in the Myoviridae family.The optimal multiplicity of infection(MOI)for PC79-13 was 0.01.The one-step growth curve showed a latent period of 30 min and a burst period of 80 min.PC79-13 exhibited significant tolerance to a range of pH levels,with pH 7.0 being the most suitable.It also showed strong resistance to UV radiation and high temperatures.The FITC-labeled PC79-13 retained its infectivity against S.pullorum C79-13.It bound efficiently to S.pullorum strains,showing green fluorescent rod-like structures under the fluorescence microscope,but did not bind to non-host bacteria such as Salmonella typhimurium,Salmonella enteritidis,and Escherichia coli.Conclusion:PC79-13,a highly lytic and specific bacteriophage against Salmonella pullorum,was isolated.Fluorescently labeled PC79-13 can specifically and rapidly attach to the host Salmonella pullorum,facilitating its detection by fluorescence microscopy with a detection limit of 10 CFU/mL and a detection time of 20 min.Therefore,the fluorescent phage rapid detection method constructed by our experiments has the potential to be applied to the rapid detection of common clinical Salmonella pullorum.
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