Isolation and biological characterization of a bacteriophage against Staphylococcus aureus

Abstract:

[Background] As a conditioned pathogen, Staphylococcus aureus plays an important role in clinical infection. Therefore, the effective prevention and treatment methods should be studied more. [Objective] To isolate and analyze the biological characteristics of staphylococcus aureus phage, and to provide theoretical reference for the alternative prevention and treatment of Staphylococcus aureus. [Methods] A phage was isolated from sewage using pathogenic Staphylococcus aureus D085 as host and called vB_SauS_SAP3. The phage was obtained by PEG8000 concentration and cesium chloride density gradient centrifugation. It was stained with uranium acetate and observed via transmission electron microscopy. The phage host spectrum, optimal multiplicity of infection (MOI), one-step growth curve, temperature sensitivity, pH sensitivity and the effects of organic reagents on the activity of phage were determined. The phage’s genome was obtained by the equilibrium phenol method and illumina sequencing technology for genome sequencing analyzed. [Results] via transmission electron microscopy, phage vB_SauS_SAP3 has a head with diameter of 60±5 nm and a tail with length of 170±5 nm. It was also able to lyse five strains of Staphylococcus aureus and one strain of Staphylococcus chromogenes. The optimal multiplicity of infection was 0.1. One step growth curve showed that the latent period and the burst period was 20 min and 60 min. The burst size was about 210 PFU per infected cell. The phage vB_SauS_SAP3 was resistanted to temperatures below 45 °C and sharply inactivated beyond 45 °C. It can maintain stable activity in neutral pH and has a certain resistance in alkaline environment, but acid environment will make it sharply inactivated. The phage vB_SauS_SAP3 were completely inactivated when treatment with chloroform and isoamyl alcohol. The size of phage vB_SauS_SAP3 genome was 41 950 base pairs (bp) and ecoding 65 ORFs by predicted. The genome include GC content was 35.42%. Phylogenic analysis indicated that the phage vB_SauS_SAP3 was a member of siphoviridae and a new staphylococcus aureus phage. [Conclusion] The phage vB_SauS_SAP3 has a narrow host spectrum and can withstand certain temperature and alkaline environment, which was a new Staphylococcus aureus phage. The study of vB_SauS_SAP3 can provide theoretical materials for the study of Staphylococcus aureus phage.

Key words:Staphylococcus aureus, phage, biological characterization, genomic analysis