Genotypic and Phenotypic Characterization of Some psms Hypervirulent Clinical Isolates of Staphylococcus aureus in a Tertiary Hospital in Hefei, Anhui

Abstract

Background

Staphylococcus aureus is a highly successful pathogen that can cause various infectious diseases, from relatively mild skin infections to life-threatening severe systemic diseases. The widespread pathogenicity of S. aureus is mainly due to its ability to produce many virulence factors that help destroy various host cells, causing disease. Our primary goal in this study was to explore the genes of highly virulent strains, to identify genes closely associated with high virulence, and to provide ideas for the treatment of infection by highly virulent clinical strains.

Results

This study collected 221 clinical strains from The First Affiliated Hospital Of The University of Science and Technology of China (USTC); their hemolytic abilities were tested. Eight isolates were selected based on their highly hemolytic ability and tested their hemolytic activity again; their phenotypes and gene sequences were also explored. Whole-genome sequencing (WGS) showed six plasmids (pN315, pNE131, pSJH901, pSJH101, SAP106B, and MSSA476), eight antibiotic resistance genes [blaR1, blaI, blaZ, mecA, erm(C), erm(T), tet(38), and fosB-Saur] and seventy-two virulence related genes. Three highly virulent strains, namely X21111206, 21092239, and 21112607, were found according the Galleria mellonella infection model. Therefore, we selected 10 representative virulence genes for qRT-PCR: psmα, psmβ, hlgA, hlgB, hlgC, hla, clfA, clfB, spa, and sak. Among them, the expression levels of psmα and psmβ, the three isolates, were significantly higher than the positive control NCTC8325.

Conclusion

Significant differences appear in the expression of virulence genes in the highly virulent strains, particularly the psmα and psmβ, It may be that the high expression of psm gene is the cause of the high virulence of Staphylococcus aureus. We can reduce the pathogenicity of Staphylococcus aureus by inhibiting the expression of psm gene, which may provide a strong basis for psm as a new target for clinical treatment of S. aureus infection.

Keywords:

• Staphylococcus aureus
• virulence factors
• qRT-PCR
• next-generation sequencing
• psm

Abbreviations

SSSS, staphylococcal scalded skin syndrome; WGS, Whole genome sequencing; PSM, phenol-soluble modulin; SpA, Staphylococcus protein A; IG, immunoglobulin; Sak, staphylokinase; ClfA, clumping factor A; ClfB, clumping factor B; FNBP, fibronectin-binding protein; fnbA/ fnbB, fibronectin adhesin genes; PNAG, poly-N-acetylglucosamine; MSCRAMM, microbial surface component-recognizing adhesion matrix molecule; TLR, toll-like receptor; IL, Interleukin; PVL, Panton-Valentine leukocidin; ET, exfoliative toxin; BSH, bacillus thiol; NGS, Next-generation sequencing; MLST, Multilocus Sequence Typing; ST, sequence type; arc, carbamate kinase; aroE, shikimate dehydrogenase; glp, glycerol kinase; gmk, guanylate kinase; pta, phosphate acetyltransferase; tpi, triosephosphate isomerase; yqiL, acetyl coenzyme A acetyltransferase; PCR, Polymerase chain reaction; vWbp, von Willebrand factor-binding protein; qRT-PCR, Quantitative Real-Time Reverse Transcription-PCR.

Data Sharing Statement

The whole genome sequences generated in the current study are available in the NCBI database (BioProject: PRJNA824222).

Ethics Approval and Consent to Participate

All isolates in this study were collected during the bacteriological analysis in the clinical microbiology laboratory of a public hospital, and patients were treated anonymously and therefore did not require ethical approval.

Acknowledgments

We thank Yuanyuan Dai and Huaiwei Lu for providing us with clinical strains.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no competing interests for this work.

Additional information

Funding

This research was supported by the National Key Research and Development Program of China (2021YFC2300300), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB29020000), grants from National Natural Science Foundation of China (32070132) and the Fundamental Research Funds for the Central Universities (YD9100002013).